Transcript for:
Understanding Microbes and Human Health

here we're looking at microb human interactions basically health and disease to do that let's define infection an infection a condition in which a pathogenic microorganism or germ penetrates the host defenses enters the tissues and multiplies that's an infection and the disease is the pathologic state that occurs upon infection by the way not all infections lead to overt disease right so and you could have an infection and be healthy right but infection can also lead to disease you can think of the disease as damage that's caused by an infection deviation from Health that's caused by an infection but again not all infections lead to disease what are the factors that cause disease well infections genics aging malfunctioning organs or systems but we're here to study infectious disease aren't we germs and uh diseases caused by germs right everything we've talked about in this semester we've talked about bacteria we've talked about ARA we've talked about fungi protozoa hel means viruses prons all of those are germs all of those are considered germs and there a that's why with your disease report coming up you need to pick an actual infectious disease something that's caused by a germ right and remember you have microbes all over your body that are not causing any problem they're with you your entire life These are known as your normal biota they can include an array of bacteria fungi protozoa viruses and they're just normal parts of your biota okay and remember these microbiota they live on your surfaces remember we talked about how humans are essentially elongated Donuts right on the first day of class so we're talking your surfaces of your skin the surfaces of the inside of your mouth all the way down the tube that starts at the esophagus and ends up at the other side the anus right so that whole tube is still considered on on your tissues and not inside of your tissues right you should not find microbes inside of your tissues I'm talking your blood your organs themselves right things like that we shouldn't find microorganisms there but there are plenty and and by plenty I mean in the trillions of microorganisms on you right including your colon and your intestines and such okay we actually have more microorganisms that we tote around every day than we we have our own number of cells that we tote around every day we have more bacterial and other microorganisms living on our body then we have our own number of cells especially if you don't count our red blood cells then it's like a 10:1 ratio of microbes to our own cells that we carry around let me skip ahead again remember I said it's your surfaces that Harbor the normal microbiota right skin mucous membranes upper respiratory tract remember your upper respiratory tract includes basically it stops around your neck right it's it's your nose your nasal passages your mouth your throat all that is your upper respiratory tract where you shouldn't find microbes is in your lungs your lower respiratory tract so when when you breathe in dust and debris and microbes can make it to your lungs but remember you should have a mucco silary blanket right it's a mechanism for expelling microbes out of your lungs right so if microbes do make their way to your lungs they should be expelled from the lungs they shouldn't just hang out in your lungs the GI tract including your mouth right the tube that starts at the mouth and goes all the way to to the other side that's teeming with microorganisms the outer portion of the urethra bladder urine external genitalia vagina external ear canal external eye you see how all this stuff is on your surfaces not inside of your actual tissues and you know inside of your blood right that's where you should not find microbes that's when you have an infection right when it's starts penetrating your skin penetrating your gut lining penetrating into your body that's when you have a real infection okay now they are they are finding some microbes in the lower respiratory tract you can find them in the placenta amniotic fluid and fetus these were all sites that were traditionally thought to have zero microb Iota but we are finding some Trace Amounts you know some small amounts but it's not a big it's not a big site of of microorganisms right and we all know by now the benefits of the normal microbiota right these microbiota they take up space just by taking up space and not causing harm that's a great feature of your normal microbiota CU imagine I told you happens if you know you kill off your gut microbes for instance well that frees up that space for SE or some other nefarious microbe to take over and cause you know disease they can also help you to some extent too you know that your gut microbes they can make vitamins for you they can help in the digestive process as well you know so they they can be beneficial to some extent as well now what are the factors that make you more susceptible to infection um most of us are familiar with this right age very young children are more susceptible to infection because their immune system hasn't fully developed old as well very old you know at this point your immune system is more uh compromised it's not as robust as when you were younger genetic defects or a pregnancy Surgery organ PL uh transplants other underlying diseases chemotherapy immunosuppressive drugs stress fatigue stress is a big one stress can also lead to all kinds of infection as well okay so if it's your normal biota your normal biota that causes the disease this is known as an endogenous infection okay this can happen but it's usually if a bacteria gets introduced into a site that was previously sterile okay so for instance if I cut if I cut my arm and that staff that happens to be on my skin makes its way into that cut well that cut was sterile but I cut my skin and that normal biota went where it shouldn't go and it gave me an infection right or think of a UTI right a UTI Ur urinary tract infection some microorganisms made their way up the urethra where they shouldn't go right and that could cause an infection there so think of normal microbiota but just making their way where they shouldn't be like through a cut or you know up their urethra or some other place where they shouldn't normally be this can lead to an endogenous infection so where does your normal biota start where do we get our normal biota well when you're first conceived right you're a fetus and it was first believed that you know the fetus in the amniotic sac you know is completely sterile but now we know you're not completely sterile in the amniotic sac there are some some viruses that can transverse the amniotic barrier right have you've heard of zika virus zika virus that can make its way through that barrier there are other microbes little microbes here and there that can make their way into the fetus before it's born but for the most part for the most part the fetus is relatively germ free right the fetus is relatively germ free it's upon birth right there's exposure that occurs during birth when the baby becomes colonized with the mother's vaginal biota during birth you're in inoculated think about you're inoculated by your mom's skin as you're born right and that's your first inoculation of true microbiota and then you can also gain sugars through breast milk for healthy gut bacterium breast milk may be necessary for maintaining a healthy gut micro uh microbiome for the baby as well so it's really upon birth that you really pick up your microbiome ioda it's it's that's where you get inoculated by your first surroundings right which it usually include mainly your mom is a source of your earliest microbiota okay let me skip ahead here all right so more terminology for us real quick a pathogen what is a pathogen a pathogen is a germ or microb whose relationship with the host is parasitic remember it's a type of symbiosis where one member is harmed and the other it benefits this results from an infection okay um a pathogen by the way it becomes nutritionally dependent on the host right a pathogen typically becomes nutritionally dependent on the host a true pathogen is one of is the scariest pathogen a true pathogen is a pathogen that's capable of causing disease in healthy persons with normal immune system so think of like Ebola right you could be perfectly healthy and be exposed to Ebola and you're coming down with Ebola it doesn't matter how healthy you are right so Ebola is considered a true pathogen whereas other pathogens they may be more you might be way more susceptible to them if you're a young child or elderly or if you have AIDS or such what's an opportunistic pathogen an opportunistic pathogen is one as its name suggests that can cause disease if you're defenses are compromised several of the bacteria that we work with in the lab are considered opportunistic pathogens if you get some on your skin and you go and immediately wash your skin with soap and water you're going to be just fine right but if you have a cut and they get into the cut or if you don't wash your hands and you take it home somehow and it gets into your food right these types of things are opportunistic path pens if you're careless if you're not using proper techniques to sanitize then these can cause harm let me skip that let's talk about virulence virulence is the degree of pathogenicity the more the more capable a microorganism is to cause disease the more virulent it is right so Ebola I was just talking about ebola ebola would be highly virent it has a high degree of pathogenicity ability to cause disease is what that means and virulence factors this is almost an all-inclusive term virulence factors are any characteristic or structure of a microb that helps it to cause disease you can think of it that way so virulence factors are many many let me put it this way anything that helps a microorganism cause disease uh is considered a virulence Factor anything so for instance let me give you an example we we learned that fim you know the bristles fim help you to attach to tissues right would that be a virulence Factor yeah because without those fim e you would have a harder time attaching to the tissues and causing disease right does that make sense so even even even an adherence structure like fim is considered a virulence Factor because with think about if I took this away would it be less capable of causing disease if the answer is yes it's a veillance factor right does that make sense so what about capsules right remember capsules this sugary layer that you know it prevents phagocytosis by white blood cells you know white blood cells have a hard time with capsules is that a veilance factor then yeah so capsules are veilance factors fime are veilance factors right if if I'm a bacteria and I make a toxin and that causes disease is that toxin a veilance factor that's a virence factor right if I if I am resistant to antibiotics is that a virence factor sure that's a virulence Factor you see what I'm saying anything that helps the microb caus disease and prevents it from being destroyed is a virulence Factor so endospores would be a virulence Factor because that makes it harder to treat and harder to clear right you see what I'm saying anything that helps the microbe be pathogenic is a veilance factor okay anything um and so the most pathogenic organisms have happen to have usually happen to have the most virence factors right so if this organism has 12 different virulence factors it's most likely a pretty bad pathogen right does that make sense okay that leads to a concept known as infectious dose ID for short the Infectious dose is the min minimum number of microbes required for an infection to proceed I know it's weird concept but one of almost any microb one of a microbe is not going to make you sick right so if I'm exposed to one bacillus andthis bacterium I'm going to be fine right so how many bacterium do I need to ingest or get in my body before I get get sick right how many how many basill andthis have to infect me right this is known as the Infectious dose and they figured this out experimentally you know usually they start with mice you know or other organisms that for instance they'll expose mice to X number of this bacterium and then they'll figure out at what point do at least half of the mice get the disease that's called the id50 right id50 would be how many microbes do I need to inject for half of my sample to get the disease right and it it shouldn't surprise you that the more pathogenic the virus or the bacteria the more pathogenic it is would you expect it to have a lower id50 or a higher id50 what do you think lower yeah yeah think about it if you're better at causing disease you're a true pathogen it's most likely going to take fewer of you to cause an infection and cause disease right if you're less pathogenic then it probably takes way more of you to cause a disease right and so it doesn't it it's not uniform for all different microbes right for me to come down with this infection and this other infection you know it may require totally different amounts of inoculum totally different amounts of bacteria I'm exposed to right you see what I'm saying depending on how pathogenic it is and so each pathogen has a different the most scary bacteria I think they've estimated like 12 to 18 individual bacteria are enough to give you a disease right so that's scary okay and again your genetics plays a role to your susceptibility to different diseases your overall health your overall health and when you're exposed as well okay if you ever notice like with covid for instance some people caught covid and they were pretty much asymptomatic and they never showed any signs or symptoms right that could happen you know that that could happen but then other people were exposed to covid and unfortunately they got really bad pneumonia and passed right what's the difference well it's genetics Health number of different factors so diseases don't affect everybody the same way right some people come down with a virus and then it's it's it causes it reeks havoc on them right some some other people come down with with the same virus and they're fine right again it all depends on your genetics your overall health okay let me skip ahead here so how do how do um microbes cause disease in a host first of all the microbe has to find a portal of entry entry into what entry into your sterile areas okay places where microbes are not supposed to be right like I'm talking inside of your skin right inside of your body so we need a break in the skin we need a break in the GI tract we need to go through the lungs out the other side right we need to get in we need to find a portal of entry because guess what if I'm just hanging out on the surface of the skin I'm not going to be causing disease right I'm going to be causing an infection how do we attach remember there are different ways that these microbes can attach to your surfaces fim capsules can help with attachment even slime layers can help with attachment surface protein what about viral Spike proteins right all of these things help with attachment then surviving the host defenses if I get into the skin I'm not I'm not on easy street am I right if I get into the blood well guess what a big fosic white blood cell is just going to come along and Gobble me up right so I need a way of like avoiding the host's immune system right so can I avoid phagocytosis by the white blood cells of the host can I avoid death inside the fosite so this is a trick that I don't know which one of you is doing TB as your project yeah TB but that's what TB does TB gets phagocytosed by the white blood cell but then it lives inside of the white blood cell it doesn't get killed by the white blood cell so it's got this trick up its sleeve it's like yeah you can gobble me up but I'm going to just live inside you forever right isn't that interesting right and then the absence of specific immunity as well okay so then now again just because like this is this is probably sufficient to cause an infection right this is sufficient to cause an infection but not all infections lead to disease right for for for it to lead to disease we need to damage the host we need to damage the the person that's infected right how do we damage we could release enzymes we could release toxins that damage the host tissues we could cause a m massive allergic reaction in the host you know cuz sometimes what happens is certain pathogens can cause an like almost like an autoimmune response in the host where the the host's immune system goes so overboard that that causes dead damage right they can cause epigenetic changes in the host's chromosome this is kind of above our pay grade for this class and then what do we timately have to do exit the host yeah because keep spreading right that's why it's called communicable right we want to keep spreading so we got to find a portal of exit a lot of viruses and bacteria they exit by respiratory means right so if I'm coughing sneezing if I'm you know you know if if I'm uh spitting into a water source right this is all ways of exiting my body through salivary glands respiratory tract but what about also fecal matter blood eurogen tracts skin cells right all of these are ways of exiting the host so again you know these are steps that are required for causing pathogenesis for causing disease and by the way all of these are yes all of these are virulence factors right anything that helps you is a veillance factor Factor right anything that helps you cause a disease and prevents you from being treated is a verance factor okay just gonna skip ahead here so remember that the placenta the placenta is a good barrier against microorganisms but it's not perfect okay some germs can cross the placenta and be spread to the fetal tissues okay but many diseases can be spread many germs can be spread to the fetus during birth that's the most common time to pick up the microbes during the birthing process but remember some germs can cross the placenta I know we had a big scare a few years back with zika during the Olympics uh so that's an example of a virus that can cross that barrier okay but otherwise your barriers are pretty good right um your respiratory tract like like I said when you breathe in germs your lungs have this way of have Celia to beat that debris out of the lung um when you ingest germs like eat germs they go down to your stomach where they're killed by the very acidic pH of the stomach your skin is great at keeping germs out of your system your eyes are constantly flushing your ears are of ear wax right all of these things are helping keep microbes out but when they penetrate those sources when they bypass those barriers this is when you lead to infection and disease and these are some common infections of the fetus and neonate the acronym torch toxoplasmosis other diseases that's like allinclusive rubella cytomegalo virus herpes simplex virus these are all common complications during birth or to the fetus itself and I told you about adhesion being very important for the disease process right if the pathogen cannot adhere to the host then the host is not susceptible to that pathogen and remember there are many different adhesion molecules so here's a list of different microbes and their adhesion mechanisms so for instance ecoli E coli adhere to your intestinal cells your microvilli with fim remember fim those short projection buril like projections pomonis orosa also use fim but they have slime layers as well so they can use their slime slime layer for adhesion as well right what about the flu for instance influenza virus notice how it uses its viral Spike proteins right so different germs have different ways of absorption right to adhere to the cells okay and remember all of these mechanisms of adher uh adherence all of these are examples of virence factors remember what I said last time what is a virulence factor is anything that can help a germ cause disease right anything and and adhesion is vital in the disease process so if you can't adhere you can't cause disease so adherence factors are in and of themselves virulence factors okay now once you have adhered to the cell you need to survive the host's defenses right what do they mean by host defenses what they're talking about is your immune system you know if you if you have a healthy immune system that means your fosic white blood cells are constantly looking for Invaders your B cells your t- cells they are constantly on the lookout for Invaders and they're going to kill any Invader right so how do you survive the host's defenses if you're a germ how do you survive well they have different me mechanisms like antiago factors these are factors that either prevent the microorganism from getting phagocytosed right or allow the organism to survive inside of the fosite the fosite is the white blood cell and they kind of work like amoeba you know how amoeba work they have pseudopods but then they can wrap their membrane around some food and bring it in right that's how your white blood cells work now not all of them but they're called the fosic white blood cells these are your dendritic cells your macro phages your neutrophils if you've ever heard of those we're going to cover those later on but those are the three white blood cells that are fosic they gobble up Intruders right so either you can make yourself so you're invisible you're you're cloaked you know and invisible to the fosic white blood cell or you could make it so even if you get phagocytosed you don't get destroyed inside of the phagocytic white blood cell right so those are the two ways by which you can you know survive you could also try killing the fosy so you know when you get inside of the fosic white blood cell you could destroy that that white blood cell too do you guys remember for instance capsules right capsulated bacterium well the capsule helps evade the fosic white blood cells because it's hard for a fosic white blood cell to determine if that capsule is an Invader or just sugar you know what I mean another thing is uh you've heard of like TB tuberculosis microbacterium tuberculosis this is a organism that gets inside of the maccrage and then lives inside of the maccrage it's adapted to just flourish inside of the maccrage right so that's another example of evading the host defenses then we can cause disease remember remember one thing infection does not necessarily lead to disease you can have infection and not lead to disease because disease means a deterioration in the host's health you can be infected with something and not show a disease like I could be a carrier for salmonella I could be a carrier for Co and not ever show the disease right that's called a uh asymptomatic carrier right but if the organism has enough virulence factors like toxins or other types of toxic substances it can lead to disease if it damages my tissues enough it can lead to disease if it lices my cells like a virus that lices cells that could lead to disease right again if you damage the host this can lead to disease how can you do that well you can secrete different enzymes or toxins if you secrete enzymes or toxins this can cause tissue damage leading to disease you can cause an overreaction of the body's defense this means that you know you know when when you have a intruder you know how your body responds to that Intruder there's like a inflammation that happens and a response well some diseases can trigger an overreaction by your body right so it's like a over re response an overly a aggravated response and that could lead to damage by itself in fact they were hypothesizing that you know when people had the really bad reactions to covid it may have been a body's response an overreaction of the body to covid right uh syphilis is another example did you know I don't any of you doing syphilis as your disease no well syphilis has three tiers three phases there's primary syphilis secondary syphilis and then tertiary syphilis the primary and secondary syphilis is treatable but then when it progresses to tertiary syphilis it's not treatable anymore you know why because by that point the damage caused by tertiary syphilis is not because of the bacteria anymore now it's because of your own immune system overreacting causing all the damage is that interesting so you know your own body could be triggered into causing tons of damage because it's overreacting right uh so those are the main ways we're not going to talk about epigenetic ways or Gene transcription things like that okay so again what are these enzymes I speak of these enzymes that cause damage to your tissues well um mucinase catinas hyaluronidase these are all enzymes that break down your tissues or mucus right hyaluronic acid is important in your tissues to hold your cells together this is mucus mucus is important because it keeps germs off of your epithelial cells keratin your cells are surrounded with keratin that can break down the Keratin so if you're breaking down the Keratin you're breaking down the hyaluronic acid you're breaking down that mucus you could actually start breaking apart the tissues right and B boring into the tissues okay and that can cause damage right okay I think you can see it kind of here let me see if I can get this to oops I'm going to try to get this to zoom but it's not working with me here you can see there are enzymes secreted and notice what these enzymes do like hyaluronidase or keratinase you know these types of enzymes they chew up the connections between cells and now the cells have leaky spots and the bacteria can grow through the Leaky spots to the other side and they can basically penetrate from one tissue to the next by breaking up the connections of the tissues one of the reasons why your skin is such a good protection against germs is because you know how those tight junctions and those tight connections between cells right well these enzymes break up those connections and then the bacteria can just kind of grow through those pores right and that's how the bacteria can get in even without a cut because what's the normal way for bacteria to get in well I I get a cut right and now I got a cut that invites the bacteria into my system right but even without a cut some bacteria can release enzymes that chew up you know the connections between my cells and then they can grow into those connections right and these are called EXO enzymes because exoenzymes are enzymes that you secrete into the environment right remember we also talked about another type in lab we talked about uh hemo as well remember hemo um some bacteria release hemo license that can cause red blood cells to get destroyed right there's Alpha homolysis Beta homolysis so another type of exoenzyme that causes tissue damage are the Hemo license like streptococus pyogenes make you know in your throat now toxins are another type of exoprotein these proteins that are secreted toxins there are um toxins are chemicals that are you know hazardous to your cells they they're toxic to your cells they cause cell damage that's what they do they cause cell damage they can be produced by all different kinds of microbes fungi can make toxins bacteria can make toxins you know um viruses can't make toxins by the way viruses cannot make toxins so exotoxins and endotoxins are the two types of toxins that we need to learn about are two types of toxins endotoxin and exotoxin okay those are the two we've already talked about endotoxin we've already learned about endotoxin who what does lipid a yeah remember lipid a I told you that it's so important to understand gram negative bacteria because the outer membrane of gram negatives has LPS remember lipopolysaccharide and the lipid portion of LPS is is called lipid a and that lipid a is really toxic and it's known as endotoxin so that's when you go in the clinic when they do a endotoxin screening when they're looking for endotoxin that's what they're referring to there is no other endotoxin lipid a is endotoxin lipid a is what they're referring to right and it's made out of lipid it's a it's it's not a protein it's a lipid okay but exotoxin a protein that's a protein that's a protein that's a protein and there's many different proteins different organisms produce different exotoxins there are so many different exotoxins so you know clostridium botulinum remember we talked about clostridium botulinum which causes botulism uh that has a toxin the botox the botox toxin or the botulinum toxin that's the same toxin they inject into people's foreheads and stuff to prevent wrinkles right so that's a toxin what about clostridium tetani claustrum tetani tetanus that's another toxin what about Anthrax toxin that's another toxin right CI CI C stum defil makes a toxin that irritates the co and causes colitis uh shagel shagel makes a toxin the suar toxin that causes disent bloody diarrhea right so many different bacterium and fungi can make toxins and different toxins they work in different ways and they are what they're made out of what protein proteins which means they come from genes right whenever you see something's A protein that means it comes from a gene right because a gene codes for a protein does that make sense so the Sha um toxin is from shella's Gene it's a sha toxin Gene right isn't that interesting so for instance um I told you about that harmful strain of eoli right did I tell you about that that I told you there was a eoli strain called 0157 H 7 and that's the scary eoli you know when they say oh Jack in the Box watch out for this ecoli you know just making up an example but that eoli is not your friendly everyday eoli okay that eoli um picked up through horizontal Gene transfer right through horizontal Gene transfer that eoli picked up the shot toxin Gene from shagel does that make sense so it picked up that toxin from from shagel from a different species and now this eoli it has the gene for the suar toxin so it makes the shot Toxin and that causes dissenter that causes bloody diarrhea you know loss of water hypo volumic shock and even death right so you see how that works so those genes can be shared through horizontal Gene transfer which is kind of scary okay so again exotoxins they are proteins right whereas endotoxin is lipid a so can gr positive bacteria have endotoxin yes only gr negative only gram negatives would have endotoxin because the endotoxin is part of the outer membrane of the gram negative bacterium only yeah but but gram positives and gram negatives could have exotoxins depending on but that doesn't mean all bacteria have toxins right not all bacteria produce an exotoxin but some do and those are the ones that typically cause disease the you know shagel causes disease uh costum tetani causes tetanus you know the ones that Co that make an exotoxin typically cause disease right now what do we need to know the difference between exotoxins and endotoxins okay again we need we know that exotoxins are proteins endotoxin is a lipid lipid a exotoxins um one thing I want you to know about exotoxins is they are heat liable they they can be destroyed by heat exotoxins can be destroyed by Heat usually why do you think that isable cuz it's a protein proteins can do what when you heat them den and when proteins Den they lose their shape when they lose their shape they don't work right and do proteins just renature once they're denur no that's right they stay denatured so exotoxins can be denatured with heat right but what about endotoxin what do you think about that can I just heat it up and destroy that endotoxin no it's a fat it's a lipid can you destroy lipids by just heating them up no so you can't just cook you know you can't just heat up endotoxin and then it's safe to eat that food or something you know if there's a lot of endotoxin in that food it doesn't matter for example how much you cook that food it's still going to be toxic to you but if there are exotoxins in that food then maybe you can destroy a lot of it by cooking it thoroughly right so knowing that if you have food food that smells bad and it's a little spoiled do you think just cooking it will make it perfectly safe no because any endotoxin in that food is going to remain toxic whether you cook it or not right so when food's spoiled you cannot just cook it and make it safe to eat right does that make sense because of why well two reasons really one is lipid day and the other one is endospores right so neither of those will be destroyed by cooking right does that make sense cool what else should we learn about these [Music] um so uh exotoxins because because they are proteins your IM immune system is really good at identifying them as foreign right you know your immune system your immune system has antibodies right and all this stuff your immune system is really good at identifying foreign proteins right so exotoxins are what's called antigenic um they're antigenic that means they elicit a immune response they trigger an immune response in fact did you know a lot of vaccines are just a protein did you know that so for instance uh the the the tetanus vaccine is just the tetanus protein the Tet the tetanus toxin protein they injected into you but it's a denatured form it's a it's called a toxoid it's like a denatured form of that toxin what about the covid vaccine what is the covid vaccine do they do they vaccinate you with the entire covid virus no what what is the co vacine know it's just the spike protein just the spike because viruses have Spike proteins on the outside right well the covid vaccine is just the spike protein and that protein alone triggers your immune system right to make antibodies but what about what about this look what about endotoxin is endotoxin a protein no it's no it's a lipid and because it's a lipid your your immune system has a tough time figuring out its foreign and fighting it right it's like it's a lipid it's a weird looking lipid should I make antipodes against that I don't know so it basically it does not it's not antigenic it does not elicit an immune response right does that make sense so your immune system has a it doesn't get as alerted right foreign protein elicits an immune response foreign fat doesn't really so what do we need to know again exotoxins are more antigenic than endotoxins they elicit a immune response right and production of antibodies production of antibodies whereas lipid a would not lead to production of antibodies okay those are the big things and again I told you about hemo license as well which is a type of EXO enzyme right hemo license some bacteria do not produce hemo license and those would exhibit gamma hemolysis some produ hemolin that partially rupture red blood cells those would result in Alpha homolysis and some completely destroy completely destroy the red blood cells and that's beta homolysis have we looked at this yeah we we have looked at this right so so these are exoenzymes these are enzymes secreted by bacteria like streptococus pyogenes that rupture red blood cells these enzymes rupture red blood cells and that's why strep throat is so bad like if you get strep throat it's your throat gets so sore and that's because that streptococus pyogenes is in there it's penetrated into the back of your throat and it's starting to even rupture red blood cells and that's causing inflammation and pain right you see what I'm saying and again again some damage and some disease can be caused by excessive host response this means that your immune system going too uh over the top in response and it says here from your textbook scientists speculate that the symptoms of Long Haul covid-19 which is persisting for months uh it's caused by overstimulated immune response and that makes sense because you know these people are treated of the virus the virus is gone but they still have some symptoms and it may be due to that overstimulated uh response that overstimulated host response we're going to skip epigenetic changes okay so a couple a couple of different ways of you know patterns of infection you can have infections that are highly localized to a particular spot think of like if I get I don't know a a staff infection you know if you get a staff infection a lot of times it's like a circular spot on your skin that's called a localized infection right but what about systemic systemic means that it's basically spread throughout your body the the organism has somehow gotten into your system and is usually traveling around the circulatory system and it's everywhere right that's a systemic infection so if you ever had like chickenpox most of you have not had chickenpox because there's a vaccine I had chickenpox cuz believe it or not I'm old now and I was born before the vaccine I was born before the chickenpox so I remember having chickenpox I remember I was covered in these dots and that was a systemic infection that's systemic that's everywhere right so again localized infections they remain at a specific site on a specific tissue think of boils warts fungal skin infections right systemic obviously it means it's made its way throughout the fluids in the bloodstream or the lym fluid inside of your body and it's spread throughout the body there are fungal infections that could become systemic there are bacterial infections that can become systemic viral infections that can become systemic all of them can become systemic okay in fact bacterial infections you know they can become dangerous because you could have for example you could have a staff infection on your arm but if you leave it untreated you leave it and you don't treat the staff infection it could remember they release exoenzymes that start digesting the tissue and then next thing you know it's in the lower levels of the skin and then it penetrates into the blood right and it gets into the blood next thing you know you you have systemic staff infection right so that's one of the problems with bacterial infections is yeah sure it's can start here but it could spread throughout the body did you know uh this is also you could die for instance did you know you could end up dying from uh gum disease right you know your gums are inflamed and infected you know and then you just don't pay attention to it you don't go to the dentist you know why well guess what that infection that bacter in your gums in your in the in your tooth right and your gums well eventually it can make its way into some capillaries down there and some veins and next thing you know it's spreading throughout the body it go up to the brain and next thing you know you've got a systemic in life-threatening systemic infection from just a simple cavity or from a simple gingivitis a gum disease okay we're going to skip focal and mixed and primary secondary I'll just mention primary secondary a primary infection is the initial infection and then a secondary infection occurs when a primary infection is Complicated by another infection so this happens a lot you can see this happening with the flu for instance you know for instance sometimes people catch the flu the flu virus and that's their primary infection but because they're like not feeling well and then the flu can cause you know um you know fluid buildup in the lungs and pneumonia and then next thing you know you have a bacteria in the lungs as well and the bacteria is causing helping cause pneumonia so you could for instance come down with the flu virus but later on pick up I don't know some kind of bacteria in your lung and now you have a secondary infection right so that could happen and that's pretty common or you could catch Co right you could catch Co and then next thing you know you pick up another bacteria and then that complicates everything right so that would be a secondary infection so when when a doctor if a doctor were to prescribe antibiotics for covid right it it doesn't make sense right because CO's a virus right CO's a virus but the only time it would make sense to prescribe antibiotics to a patient with covid is if you susp ECT what you suspect there's a secondary infection maybe in the lung of the bacteria and that's making it worse you know what I mean so so yes there are cases where it's good or you know where a doctor May prescribe antibiotics for a flu or a covid or some kind of viral infection but only if they suspect a secondary bacterial infection right or a fungal infection or something like that as a complication but if you just have signs of the flu and that's it well then it would not make sense to prescribe antibiotics right so the flu would always be the primary the flu would be the primary and then you know and because what happens is that stresses your body you get less sleep you're more stressed your body's in a compromised State and that makes you more prone to getting another disease yeah and you know diseases can be acute which means they come on strong they come on quickly but they usually leave just as quickly right or chronic where they could progress and persist over a long period of time sometimes your whole lifetime right now this is one I enjoy talking about because not many people think about this but when it comes to a disease there are what are known as signs of a disease and symptoms of a disease and a lot of times people use these terms interchangeably but they're not interchangeable terms okay what you need to know is that signs are things that you could measure okay signs are things that you can measure like a fever like a fever I can measure a fever by sticking a thermometer on you right does that make sense I can measure a fever I don't need you to tell me that you have a fever I could put a thermometer on you and figure out that you have a fever does that make sense that's why it's a sign a symptom is not measurable it's not measurable but it's something you feel as a patient so what would be a a a a symptom like headache headache yeah can I tell if you have a headache there is there any way I can measure headaches no no exactly temperature yeah temperature I can measure it's a sign but headache no I can't measure it's a symptom you see what I'm saying together that makes the syndrome right so the syndrome of the signs and the and the symptoms but signs are not symptoms okay signs are measurable symptoms are not this is why it's so hard to be a veterinarian you know like when I take Gizmo and Wicket to the vet you know it's hard because I'm like well Wick's not acting right you know but Wicket can't say oh it's because you know this hurts or that hurts you know what I mean Wicket just doesn't act right you know what I mean so it's tough to be a vet because you have to go off of which one you have to go off of the signs you can't ask Wicked you know about the symptoms Wicked can't talk right right yeah so it's hard to be a vet you know if you're a doctor then you've got both right as long as the patient is alert and awake and not in a coma or something right you can ask the patient what's wrong he's like oh it really hurts here you know what I mean but Wicked can't say it really hurts here you know so that's the difference in fact my knowledge of signs and symptoms got me out of jury duty one time would you like to hear this story of how Dr D got out of jury duty with his knowledge of science um I didn't want to get at first of all quick disclaimer I did not want to get out of jury duty because I do believe in my civic duty and I believe that you know I should definitely do jury duty but you know this this time it was bad because I I I kept you know postponing it and then they wouldn't let me postpone it to the Su I just wanted to postpone it to the summer when I have free time but the latest they would let me postpone it was finals week and I was like I can't miss finals week you know so I needed to get out of jury duty okay this is the this disclaimer but anyway it was about one guy who punched another guy okay that was what it was all about it was like a simple assault this guy punched that guy and the during vo dire where they figure out if they want to keep you as a juror the lawyer for the defendant um said that you know I'm going to prove that my patient was in ex or not patient my client was in extreme pain due to the punch and I pounced on it's like do you guys have any objections with me with my premise here and what do you think I said I jumped in right away with a objection what do you think what was wrong with that statement I'm going to prove that my client was an extreme pain due to that punch it's a symptom can you prove pain no so I raised my hand and I said absent of broken bones or blood or bruising you're going to prove that your client was in pain and she said yes and I said well I would never be satisfied and she said why and I said well because pain is a symptom symptoms cannot be measured hence the 0 to 10 scale when you go into the doctor doctor don't have a panometer they cannot measure pain they need to ask you it's subjective to the patient if your entire premise says you're going to prove pain and proving pain is literally impossible well then I will never be satisfied the next thing you know I'm off that jury right so you see sometimes science comes in handy and I I I even glanced over at the you know the uh uh the I think the defendant I think that was the plaintiff I was talking to the GU over to the to the defendant table and the lawyer was taking notes he's like oh yeah yeah that's a good point that's funny stuff but yeah you cannot prove pain it's impossible to prove pain there's no way to measure pain this is why they ask you when you go to the doctor they say how much pain are you in Zer to 10 cuz they don't know they they have no way of measuring it and they just have to go off of what you say if you say 10 they have to go with it you know they probably think you're lying because 10 means you wouldn't be able to even answer cuz you know you know what I mean um but anything above eight they're they know to give you medicines anything below eight they know to give you something else so they just it's subjective they cannot they cannot measure pain so hopefully that makes it clear the difference between a sign a symptom and together they make up a syndrome so these are signs right you see this is a list of signs if I can measure it even if you're unconscious then it's a sign right does that make sense so what are some signs of covid signs of covid fever fever yeah that's the big one cough if I'm cough actively coughing I can see that I can I can see cof CH which one chest SS yeah chest sounds with by putting the stethoscope up to your chest yeah exactly what are some symptoms of covid headache headache L of taste loss of taste loss of smell yeah I can't I can't tell if you can smell or not dizziness dizziness yep fatigue how about fatigue well coughing coughing I can see coughing I can see but chills I can't tell if you're if you experiencing chills or if you have fatigue you know or if you have a headache or you're tired you know all these things I can't tell all that okay all right so what are some of the signs and symptoms of inflammation inflammation this is the earliest symptom of disease infections can lead to inflammation okay what we have is edema edema is accumulation of fluid in the affected tissue in fact you know when things are uh inflamed when you have inflammation it feels swollen right it feels like a lump right and that that's because of a lot of Edema going on there's more fluid coming to that part that's infected right and that can lead to you know swelling swelling because there edema this fluid is getting to that site of the infection also so that can lead to pain right because if you have more fluid in in this one spot that could also lead to pain as well right you can have swollen lymph nodes often times near the site of infection if I have for instance if I have a ear infection the lymph nodes near the ear will be inflamed they'll be bigger and that's because lymph nodes are a place where white blood cells congregate okay again signs signs of infection in the blood lucco yosis lucco sites are white blood cells that's what a Lucy is a white blood cell and you have an increase in the number of white blood cells in the area Okay the the opposite of that would be lucenia which is a decrease in white blood cells so we have increase in white blood cells to the area when we have infection what's sepsis or sepia this is where microbes are growing in the blood right so you have germs in the blood this is sepsis germs in the blood so if someone's gone septic that means that it's a systemic infection organisms are in the blood if it's bacteria in particular then it's bacteria you have bacteria in the blood if it's viruses it's Veria viruses in the blood see emia means in the blood what's upia leukemia leukemia means it's a cancer actually it's it's to many white blood cells too many uh white blood cells in the blood right produced being produced by your stem cells right so your your stem cells the the homat poetic stem cells in your bone marrow they're the ones that make the white blood cells and if those hematopoetic blood cells in your bone marrow become cancerous then they just start making too many of a particular type of white blood cell that's leukemia if it's lymphoma it's it's a similar to leuk IIA it's a l lymphocytes are a type of white blood cell and then other white blood cells are just generally luyt leukemia would be some of your white blood cells growing too much right or being produced too much lymphoma would be a B cell or a t- cell you know over abundance right so yeah either way it's a blood disease Leukemia Lymphoma are blood diseases but they are Cancers they are Cancers whereas these are the presence of these organisms growing in the blood y good question and again not all dis not all infections result in overt disease right not all infections result in disease these are called asymptomatic infections or subclinical infections inapparent infections these are all terms that refer to having an infection but not showing signs or symptoms of disease right so for instance that was a big problem during the pandemic right during 2020 2021 you know when the pandemic was spreading a big problem was all these asymptomatic carriers there were people who were perfectly normal you know they they didn't feel bad they weren't coughing they weren't they didn't have a fever but they were walking around as little human incubators you know what I mean spreading the germs around right so these are known as asymptomatic carriers all right and lastly do you remember at the very end these germs need to leave your body right they need to find some kind of portal of exit so they can spread to the next host right and there's so many ways for The Germ to spread right it could be coughed out sneezed out through the spit it could be sexual contact it could be through the feces it could be through the skinto skinin contact there's many different ways of you know exiting the host right Co was spread mainly by people coughing right coughing okay again escape from the lower and resp lower and upper respiratory tract through the mucus sputum nasal drainage coughing sneezing skin slopping off right your skin feal right any kind of enteric bacteria can be spread through the feal matter also worms can be spread through the feal matter as well urogenital tract you know the urogenital tract especially STI sexually transmitted diseases blood how about through the blood you can spread diseases through blood blood contact as well sometimes it could be direct blood contact and sometimes it could be through a vector you know like a tick or a flea or a mosquito could bite me and then it could bite you right and spread that blood disease plas plasmodium plasmodium exactly like a malaria that's right so when where we were where we left off we're about to talk about the course of an infectious disease so what happens when you come down with a disease what are those phases called so when you come down with a disease the first thing that happens is that you feel just fine as The Germ replicates inside of you this is known as the incubation period uh think of yourself as an incubator the organisms are growing within you but there are no signs or symptoms yet this is called the incubation period following this we enter the prodal period this is where you start noting signs or symptoms this is for example the morning you wake up and your throat's scratchy and something doesn't feel right that's the pmal period next is the acute phase this is where you have the most pronounced signs and symptoms and those pronounced and clear signs and symptoms of the disease uh up and then hopefully you reach the final stage here convalescence where you fight off the disease you fight off the infection and you are your your symptoms are declining right this is known as convalescent so we can if you plot it out with time versus intensity of symptoms here you can see at first you have no symptoms and during the incubation period there are no symptoms then remember you wake up that one day with that scratchy throat this is the pmal period where you start to feel symptoms and keep in mind one thing I want you to know about the pmal period is that even though the signs and symptoms begin to appear they're not very clear okay it's very difficult to be diagnosed properly During the pmal period of a disease right so for instance when you show up to the doctor and say my throat's kind of itchy today or scratchy and it hurts when I swallow well the doctor could say you're either coming down with a cold you could be coming down with the flu you could be coming down with covid you could be coming down with strep throat we don't know right so it's very hard to be diagnosed During the permal period but it's the acute phase where you know the signs and symptoms are really presenting themselves and you have full-on symptoms that's when you can be properly diagnosed okay and then you reach the height of infection this is when you feel the worst and then hopefully your body fights off the infection so that levels off and then we can enter the convalescence period so that you get better hopefully it doesn't do this number where it continues onto a continuation period for a chronic disease but hopefully we are cured right our body fights off the infection and we go back to zero symptoms again these are known as the stages in the course of an infectious disease now for some very important terminology about how we pick up these germs and you might you might want to keep this in mind for your disease reports as well so when we're talking about germs we need to understand the difference between a reservoir of germs and a source of germs what is a reservoir the reservoir is is defined as the primary habitat in which the n in the natural world from which a pathogen originates think of this as the the normal place where you would find that pathogen right where the pathogen lives okay so for instance uh you would find certain amiba in the soil and that's just where they live that's their normal habitat those amiba live in the soil right compare that to a source a source is not where it's not necessarily where the germ lives it's where you happen to pick up the germ okay it's distinct from the reservoir it's where you acquired the infection so for instance if I touch a door handle and I pick up covid virus from that do door handle do you think that's the reservoir for the for covid virus SAR zoov Source no it's the source it's where I picked up the SAR cov2 but that's not that doesn't mean they live on doorknobs they don't live on doorknobs they can be transferred to a door knob and then transferred to you you see the difference sometimes the source is the reservoir so for instance if I get an amoeba infection and it's because I went running around in that muddy soil then the source was the reservoir does that make sense but the source isn't always the reservoir I could pick up uh uh like I said a flu by touching a tabletop but that does not mean the tabletop is where the flu flourishes right does that make sense you see the difference between a reservoir and a source could you do another example it doesn't make sense but since it's so close what's another example yeah another example would be let's say Okay um if I eat a potato salad right and I come down with salmonella is that the source or the reservoir source source because salmonella doesn't it it doesn't naturally thrive in potato salad it's not like it's it's just every potato salad is teeming with salmonella it's salmonella is an enteric bacteria does that make sense enteric means gut right salmonella salmonella's Reservoir where it normally lives is in your gut right in the guts of animals like chicken in the guts of humans you can find salmonella that's a reservoir right but if I get salmonella poisoning from eating chicken salad or potato salad well then that's because somebody didn't wash their hands and prepared my my salad and then I ate that you know and I got sick so that's a source if it's if it made you sick but that's not normally where they come from That's The Source right yeah good question good question so I have a question if a dog with rabies bites me would that be the source yes the the dog with rabies would be the source and the reservoir oh it's you know why because rabies it it can only be they can only live in animals in mammals right so in that case the dog is the source and the reservoir if someone sneezes in your face they were the source and the reservoir of the cold too of the cold yeah yeah exactly right because the cold virus is its normal Reservoir people right does that make sense but if if you sneeze into your hand and touch a door knob and then and then someone else touches is that dornob that's a source right and what's a carrier a carrier is simply someone who is carrying the germ right think of someone who's carrying the germ around they've they're incubating that germ so there are many different kinds of carriers and some of them seem identical you know even though they're so for instance there's asymptomatic carriers these are infected people that show no signs or symptoms you can see this with gonorrhea you can see this with herpes you can see this with HPV um you can even see it with covid right some remember that was a big problem with covid when it first emerged um there were people walking around just fine but they were asymptomatic carriers they were still spreading the germs but not showing any of the signs or the symptoms you know and that's kind of dangerous then there are I'm not going to talk about all these different types of carriers but I will talk about convalescent carriers convalescent carriers these are the people who are just recovering from a disease but they're still carrying s significant numbers of that germ right so think of someone who just got over the flu and they're feeling better they're walking around but they're still kind of shedding that virus they they could still make you sick right that's known as a convalescent carrier how about um uh chronic carriers people who shelter the Infectious agent for long period after recovery okay and so they they just keep carrying it around with them even though they have recovered a lot of these types of carriers get redundant in some their definitions to some extent do we have to memorize this um I would want to know about asymptomatic carriers and maybe convalescent carriers that's about it then there are living reservoirs so would um so so remember Reservoir is where you normally find that particular germ right where it lives you can think of it that way if it's a living organism that it lives on then it's called a living reservoir so a human is a living reservoir for let's say chickenpox virus right a human is a living reservoir for let's say um uh uh uh herpes virus right does that make sense so there are living reservoirs living reservoirs okay and by the way um a lot of diseases are spread by insects remember we learned about those biting insects in the lab and those insects can spread disease they are called vectors we're going to talk about that in a second but a vector is a living Liv transmitter of disease okay so this is why they say mosquitoes are vectors you know ticks are vectors they are living transmitters of disease malaria mhm mosquito can spread other things yes yeah HIV not HIV like what is uh it can spread uh chicken G it could spread uh West Nile it could spread uh yeah it could spread a number of actually a number of different diseases are spread by by mosquitoes it can't spread HIV though which is really interesting no there's a number of uh things that can be spread but luckily not HIV um and the reason for that is because HIV is a enveloped virus it doesn't have a way of getting into the it doesn't have a way of infecting the mosquito oh okay so because it can't infect the mosquito the mosquito sucks your blood let's say someone's HIV positive right the mosquito will suck the blood of the HIV positive patient and it will ingest some HIV right but because that HIV can't infect the mosquito it goes to the mosquito's digestive system like its rudimentary stomach and it's digested so it it's uh the mosquito's digestive system destroys the HIV virus it digests it um whereas things like malaria it bites the patient it bites the the person and then it picks up the malaria the malaria actually did you know it bores its way from the digestive system of the mosquito it makes its way to the salivary glands of the mosquito so it it makes its way to the spit glands of the mosquito so the next person it bites that plasmodium comes out of it of its spit glands its salivary glands and it gets in there where it's biting and then it infects the next guy sometimes too mosquitoes like if they poop you know um if the if the organism is strong enough to withstand its digestive system then the mosquit will poop while it's biting and if you itch you'll introduce that poop into the bite you know so that's another way that you could pick it up but luckily for everyone HIV is destroyed in the digestive system that would have been terrible yeah yeah so so yeah yeah it's really interesting things to think about right so again if you're if you're dealing with actively ill humans you can directly or indirectly trans transm MIT a disease to another human so for example a direct mode of transmission would be a sick person you know sneezes in your face right that's pretty direct right but there's also indirect transmission like I said I cough on my hand I touch a door knob I I don't use the I use the restroom but I don't wash my hands and I touch food you see that's indirect right that's indirect transmission okay so again humans can be carriers humans can be carriers and sometimes asymptomatic carriers so just because a person looks fine and feels fine doesn't mean that they cannot spread diseases uh because remember infection does not always result in disease right so you can feel fine and look fine but you could spread disease you could be potential harboring different diseases okay and remember these biting insects are called arthropods arthropods we learned about the arthropods in the lab we talked about insects versus arachnids and if it can bite you it most likely spreads disease there's one weird exception that you know doesn't spread disease even though it bre bites you it's not known for spreading too much disease and that's we weirdly enough the bed bug um but there's many most biting insects are known to spread a host of different diseases and these biting insects living transmitters of disease are called vectors okay living transmitters of disease are called vectors so when a mosquito bites you and gives you a disease it's served as a vector so if I touch a doorknob and I pick up a disease is that is that doorknob a vector it's a source no that's that's just a source it's an intimate object um a vector has to be a living transmitter of disease and usually when they're talking about vectors they're talking about arthropods these biting insects okay which we learned about La um we talked about mosquito we talked about um ticks things like that that might okay but vectors could also include animals you know bats chickens mosquitoes here it's showing you the difference between biological vectors and mechanical vectors the difference here is a biological Vector it's it's it's infected itself right the the The Germ is inside it it's in its salivary glands or inside its blood or inside its tissues or in GI tract a mechanical Vector is not infected per se but it's picked up the germ right so imagine a fly a fly lands on poop you know it picks up some salmonella and then it lands on your potato salad so you know it was a mechanical Vector it didn't actually come down with salmonella itself it just simply touched some and then it inoculated your potato salad and like I said like I said vectors could be animals right like a chicken could be a vector but if if it's an animal if it's an animal that is the reservoir okay if an animal is the reservoir that's called the zunos okay and zunos are diseases that that are originated from animals okay I'll give you an example Pig Yeah a pig yeah pig is a big source of you know different types of zunos but uh West Nile do you guys know about West Nile Virus so what's the reservoir for West Nile Virus ah the mosquito is the vector the mosquito is the vector it be like bodies of water that's a good guess it's actually an animal type it's Birds isn't that interesting birds are the reservoir for West Nile and then what happens is mosquitoes bite the birds they pick up the West Nile and then they bite you they spread the West Nile so West Nile is technically a you know zunos because the birds are the living reservoirs right and then the vector mosquito bites them transmitting it to you it's a living transmitter of that disease yes the the mosquitoes have killed more humans than any other creature on the planet more than all the wars more than all the different more than sharks sharks are actually a minority right but you know mosquitoes are the biggest killers on the planet by far by far yeah so unfortunately mosquitoes can spread lots and lots of diseases right okay so here's some examples of zunos rabies Haun virus H virus is scary H virus this is a virus that's spread in Mouse Poop okay and it's a very scary virus too it can it can easily lead to death so if you're cleaning out your attic and you see a lot of Mouse Poop it's best to wear a respirator and be careful and not make a lot of dust because you don't want to breathe in that Mouse Poop right does that that's how you come down with hun virus West Nile Virus I already told you about that Anthrax plague ringworm toxoplasmosis tapeworm okay now let's talk about some non-living reservoirs I told you about some one example already mud right you can find the for example the brain eating amoeba is found in mud and soil right um bodies of water the air um different types of environments right non-living structures okay what else here's some more terminology we need to know just terms communicable disease this is the this is something that's important for you to know because it's the topic of your disease report you have to do a disease presentation covering a communicable disease it's when an infected host can trans transmit the Infectious agent to another host so a communicable disease can be spread from host to host contagious refers to how communicable that disease is how how well can it spread from host to host if it's highly contagious it spreads easily from host to host if it's not very contagious it's more difficult to spread from host to host a non un communicable disease is one that does not transmit from host to host right so genetic disorders are not communicable unless you pass them on to your Offspring per se otherwise they are not communicable right cool now remember I told you that you can uh you can spread disease directly right by coughing in someone's face right another this is known as horizontal transmission where you have a spread from one person to another that's horizontal transmission vertical transmission refers to from parent to offspring right so imagine if the mother has I let's say HIV and is not being treated for HIV doesn't isn't taking any medication for HIV then there's a possibility of the infant you know the fetus picking up that HIV during birth right so that would be an example of vertical transmission right so horizontal transmission spreading from person to person vertical transmission spreading from parent to offspring now the door knob let's go back to the door knob okay I said if I cough and then touch the door knob it can become a source but it's an inanimate Source right we can call inanimate sources Vehicles okay so instead of a vector vector is a living transmitter a vehicle is a inanimate transmitter right so a vehicle is any inanimate material commonly used by by humans so bedding you know like bedding or things that you commonly come into contact with utensils right things like that a fomite is an example a fomite is an anatomic object that harbors and transmits pathogen it's not a continuous source of infection yes's an example of a vehicle yes a fomite is an example of veh but but a vehicle the you know they're very very similar terms very similar terms but vehicle is technically anything that's commonly used by humans so a uh a bedding bedding is commonly used by humans right that clothes or um things like that a bed what's a bed the bed the whole bed yeah bed yeah but if I but if for example if I if I get if I get um if I pick up covid from this remote right this isn't like a common this isn't like a common thing everyone comes into contact with you know then this would be more of a fomite right so a fomite is an inanimate object that humans don't commonly come into contact with whereas a vehicle is an inanimate object that humans typically come into contact with like beding you know um but other than that I mean a lot of people just use these two terms interchangeably they they call vehicles beding I mean vehicles fomites and fomites vehicles it it's very close you know to me I I don't I'm not going to make that distinction yeah you said which one fite yeah yeah but you know what's weird they a lot of textbooks will call like doorknobs fomites but humans typically do come into contact with doorknobs so it's like why isn't a doorknob a vehicle so it's it's such a negligible difference that I would say it's not important to know um no one would like laugh at you for calling bedding a fomite or a doorknob a vehicle you know what I mean like no one would say oh you don't know you're talking they're they're inanimate objects that could be the source of disease right so some I've heard I've heard door knobs be called fomites I've I've heard door knobs be called Vehicles you know and when they're referring to the oral feal route this is that example I gave you of the the chef who used the restroom didn't wash his hands prepared the potato salad and inoculated it all with nice salmonella right and so that this is the fecal oral route you know you ingested it was because someone else contaminated that stuff with the improper food handling improper sanitation right this is why when you go to the restaurant it says employees must wash their hands it's not a suggestion it's actually if you want to work there you have to wash your hands right because if you don't you're going to make people sick they're going to sue the the company they're going to sue the restaurant and you know so it's a liability to to not wash your hands if you're preparing food okay so again water soil air these are all uh Vehicles right they're Vehicles they're things we come into contact with that are inanimate M indoor air can serve as a support medium for the suspension and dispersal of respiratory pathogens via droplet nuclei and aerosols so what are droplet nuclei these are kind of scary a droplet nuclei are tiny particles of let's say moisture right almost like like um imagine a tiny Speck of moisture that you exhale and this tiny Speck of water is so small that it stays lingering in the air for hours if not sometimes days those are droplet nuclei and droplet nuclei can spread from from person to person you know you can spread respiratory viruses this way easily so for instance if I cough and a droplet nuclei is expelled when I cough or sneeze this droplet nuclei is so small it doesn't do what normal spit does right normal spit if I'm talking normal spit goes right to the ground right and that's where this whole six foot you know keep six feet away from people came from that's actually ual aerosols those are actual um spit basically but droplet nuclei are so fine think of it as Mist mist is not it doesn't just travel six feet this mist is so fine so small that it can stay airborne for hours if not even days so imagine if I have covid and I sneeze or cough right here we could come back tomorrow and someone could breathe in one of those droplet nuclei and pick up Co that's not good because it stayed Airborne that long so there's a really uh a problem this showed us you know we saw this with the pandemic you know if you were just indoors with infected people you know it was really hard not to become sick right even if you stayed six feet away from them yeah and this is what those droplet nuclei looks look like see droplet nuclei dried microscopic residues when microscopic pellets of mucus and saliva are ejected from the mouth and nose like look this is someone sneezing um Oops why can't I zoom in I don't know why it won't let me zoom in but see here that fine Mist those tiny particles will soon dry and then remain Airborne almost like dust and those are known as droplet nuclei and this is why you know those Airborne diseases can be you know spread so easily and and also why you needed such good masks you know they wanted to use uh The n95 Masks because n95 masks are the only ones well not the only ones but the the ones that can block even droplet nuclei right does that make sense yes so would difference between aerosols aerosols are suspensions of fine dust or moisture um these don't stay airborne nearly as long so just think of this as you know aerosols are anything like it could be dust it could be something um floating around in the air but it's not necessarily as fine as a droplet nuclear droplet nuclei are so tiny and fine that they can stay airborne for hours and days yeah and um so yeah this is why to to again to prevent you catching covid you had to wear the n95 mask right but then why were people wearing the cloth mask do you think so they didn't spre so they didn't spread it as much right so if you're wearing a cloth mask or one of those simple surgical masks it's not actually going to protect you from Catching covid right cuz that's not going to filter out these particulates right does that make sense but if you cough really bad right and you're wearing a surgical mask are you going to release fewer droplet nuclei yes and if you release fewer droplet nuclei then you're keeping people around you safer right does that make sense so that's why everyone was encouraged to wear a mask whether young or old it wasn't necessarily to keep you from Catching it it was to keep susceptible people from Catching it does that make sense yeah so hopefully your understanding of this stuff makes better sense of you know other policies and other things that were in place and what was going on so again yeah you have to understand that many respiratory viruses are spread by droplet nuclei and unless you're wearing a very fine filter mask you're not fully protected yourself do you guys remember we talked about Robert cotch okay and he was the one who really developed how to link a particular pathogen to a particular disease using his four po that's how he determined the causitive agent of the disease Anthrax he linked it to the bacteria basilis andthis that's pretty cool because ever since he determined that we've been able to link all the different diseases to their causitive agent to their causitive germ here's how his four postulates work I don't think we went into detail about this in the past like how how exactly his four postulates work so let's talk about this real quick remember again there are four postulates the first postulate here is find evidence of a particular microb in every case of a disease so let's pretend okay let's pretend you have mice and they all have these these scars on them these U they're called esars actually they're black lesions right and that's what Anthrax is cutaneous Anthrax forms these black lesions called esars so uh imagine if we swabbed every Mouse with these lesions we swabbed every Mouse with those lesions and then we made like street plates we should find that bacteria that's causing those lesions in every sample from every mouse that has that those uh signs right does that make sense so every Mouse who has those black lesions we should be able to culture that basilis andthis bacteria from fair enough and it should be absent from healthy mice so if mice have a particular disease these mice have black lesions right if you take a sample and spread it on a plate you should always find this particular unknown bacteria right but what if I swab a healthy Mouse should I find that disease causing bacteria no so that's what that's what kot's first postulate States the pathogen should be able to be cultured from all of the mice who show that particular disease but it should not be able to be cultured or found on mice who are healthy fair enough yeah if you have the black scarfs I should see this Colony every time I make a streak plate if you don't show those black scars I'm not going to see that particular Colony when I make a streak plate okay now second postulate second postulate next we need to do a streak plate to isolate right we need to isolate that microb from an infected subject and cultivate it so grow it in a broth grow more of that isolated Colony okay next we need to inoculate A new mouse a healthy Mouse so we what did we do we isolated The Colony we grew it and then the third postulate injected into a healthy Mouse and and that Mouse needs to succumb to the exact same disease remember the black scars so this mouse should come down with the same black scars the same disease not a different disease the same disease right and then we should be able to take a sample from this diseased mouse or dead mouse in this case we should be able to take a sample and if we do a streak plate which bacteria should we find that same bacteria and if you wanted to confirm it you could isolate it again inject another healthy Mouse again and see the same disease again right if you wanted to you could do this 20 times if you wanted to right just to reconfirm reconfirm reconfirm reconfirm and then at that point you're like this culture this bacteria causes this disease right you see that's how kotch did it that's how he did it and then once he linked this bacteria to that disease then he went on to the next disease he said okay now let's look at mice who have this disease let's do the same thing take a swab maybe it's a throat disease all these mice have strep throat all these mice have a throat disease okay swab their throats make a streak plate isolate inoculate another mouse it gets the throat disease okay okay this is the one that causes this throat disease move on to the next disease right and so you could just knock these out you could start linking specific bacteria to specific diseases this way right that's how it worked okay and that's it for chapter 13 what do you guys think interesting