welcome back microbiologists today we will be covering lecture 19 microbial infections of the skin so let's go ahead and get started with today's lecture microbial infections of the skin if you take a look at this picture you see two teenagers that have acne acne is usually caused by a gram positive micro organism called Propionibacterium acnes now this bacteria tends to grow in the sebaceous glands of the skin those are the oil glands of the skin teenagers unfortunately are especially prone to acne because of hormonal changes that triggers an excess oil X is an oil production rather which stimulates bacterial growth okay so what happens is that they have these pus filled pimples that result when lymphocytes and dead bacteria clog the skin pores so this is a microorganism that causes this if that's so then antibiotics should usually be able to treat this correct okay let's move on before we start talking about some of the specific diseases that are associated with the skin let's take a closer look at the anatomy of the skin so this is a really nice picture and we know that skin is an effective barrier against pathogens because the outer layers of our skin are actually dead the dead cells okay they're replaced about once a month and furthermore our skin is covered in salt we know that salt will inhibit the growth of various microorganisms right we know that normal flora can grow in skin specifically we have two Staphylococcus epidermidis for example because it tolerates salt and the oils or sebum that's on our skin but one thing that I want you to notice is the passageways that exist within our skin right so you can notice the passageways between the hair follicles right here you see in the hair shaft look at this microorganisms going through hmm between the hair follicles and hair shaft through which microorganisms can penetrate the deeper tissues microorganisms can also enter through our sweat pores right here right through the sweat pores and so what happens is that once the microorganisms enter they can get deeper into the tissue and cause infection right so here we see the hair follicle where microorganisms can go deep down and we have these nice sweat glands that can provide a variety of nutrients for these microorganisms not good for us great for the microorganism we're going to be talking about a variety of diseases associated with the skin okay or microorganisms that cause various diseases of the skin so for us to understand the various terms that we're going to be discussing let's go over some basic terms associated with skin infections the first one being a vesicle so what is a vesicle a vesicle is going to be essentially a small fluid filled lesion it's like a blister okay it's like a blister now okay okay now the next one would be an abscess an abscess is going to be a localized region of pus a localized region of pus that is surrounded by inflamed tissue so this would be more like a boil or what we often refer to as a hair follicle infection the third term that I want you to know is a pustule a pustule is going to be a raised lesion that contains pus oftentimes these pustules that are pus filled are caused by invasive group a streptococcus infection more node most notably would be the flesh-eating bacteria that we're going to be discussing number four cellulitis cellulitis oh well here's a word that ends with itis what do we know about itis it means inflammation right so what type of information inflammation of the cells this actually is a potentially serious bacterial infection of the skin the skin may appear swollen red as the skin feels hot and tender and it actually may spread rapidly okay so it can be a dangerous condition the fifth term that I want you to know is Myositis here's another itis word so this is going to be inflammation of what inflammation of the skeletal muscles or your voluntary muscles so these are going to be the muscles that you consciously control to move your body now oftentimes Myositis will occur as a result of an injury or some sort of autoimmune disease that will cause Myositis the sixth term that I want you to understand is necrotizing fasciitis alright so this is what is more commonly known as flesh-eating bacteria this is going to be actually a rare infection of the deeper layers of the skin and the subcutaneous tissue this is commonly caused by Group A streptococcus bacteria known as streptococcus pyogenes we're gonna discuss this specific microorganism in a little bit more detail very quickly necrotizing faciitis known as flesh-eating bacteria you know that name flesh-eating bacteria is really a misnomer because the bacteria does not actually eat the tissue however it does cause destruction of the skin and the muscles due to the release of toxins that the bacteria will produce and as a result there is formation of a super antigen oh my word there is that word super antigen I think we've learned what a super antigen is do you remember that yes we discussed that in the last lecture alright so let's talk about our first different types of hair follicle infections now hair follicle infections there are different microorganisms that can cause hair follicle infections but the one that we're going to be discussing associated with hair follicle infections is going to be Staphylococcus aureus we know that Staphylococcus aureus is notorious for various different types of infections and this is one of the ways that we're going to be discussing this organism symptoms beginning with folliculitis okay so these are different diseases or infections in different hair and our skin infections that Staphylococcus can cause first as folliculitis folliculitis essentially is a pimple okay that's gonna be a small red bump and it may have some pus right now after folliculitis we can have a more aggressive infection referred to as a fur uncle or a boil this is going to be a larger area and pus is produced these can be very painful they're tender to the touch they're hot they're red they're red and they're inflamed right yes so if you've ever had one you know that it can be painful hmm okay now a more extreme version of this boil would be a carbuncle a carbuncle now is going to be a larger area with multiple drainage areas and as you can see in her back I mean this is an awful skin infection and there is going to be invasion of the tissue of the nearby tissue so this is a serious serious hair follicle infection okay how does this happen what is the pathogenesis if you look at this picture here we have the step lucas aureus it attaches to the hair follicle now remember in that first slide that I showed you I showed you the different areas in the skin where the microorganisms may actually enter into the different deeper tissue so here we see sifakas aureus is attached to the hair follicle which it can use to move down to the sweat glands once it's there inflammation boom in action can spread to the other tissues we have an accumulation of white blood cells now we know what that neutrophils make right what what is a what is dead neutrophils it's going to be pus so this is how you have this inflammation you have an abscess with this plug that has this dead white blood cells right necrotic material dead neutrophils so what is the epidemiology for these hair follicle infections contact transmission is usually the way that individuals get these infections from either carriers or fomites I've mentioned this in lab and lecture actually many times that if you have a family member for example that may get recurrent skin infections whether it's a boil or things like that it may be it may be possible or it's probably very probable that someone in the family may be a carrier of Staphylococcus aureus and so contact transmission would be one of the reasons that these individuals could get these recurrent skin infections such as boils so Staphylococcus aureus is definitely not normal flora of the skin and it can lead to serious skin infections so there are treatments for this antibiotics there are there that can be used however remember that Staphylococcus aureus is notorious for becoming resistant right so there are many antibiotic resistant strains of Staphylococcus aureus depending on the severity of the skin infection or this hair follicle infection wound drainage and debridement may be necessary okay and so what is AD to Bremen refers to removal of dead damaged or infected tissue the reason that we want to do this is because by removing the dead tissue or the damaged tissue it actually improves the healing potential of the healthy tissue that remains there are some preventative measures that one can take especially if you know that someone in your family or maybe you are prone to these skin infections hexa chlorophenol score hibiclens chloride sitting so this is actually something that can be very useful if someone tends to have these skin infections at the first sign of a little redness or that you think may be turning into something get a little cotton swab put a little hibiclens and clean the area just to be on the safe side okay so a hexa-core also known as knave act is an antiseptic anti septic agent that can be useful in the treatment of hair follicle infections all right so we're gonna talk about scalded skin syndrome this is the first not infection or it is an infection but disease an actual disease or it's referred to as a syndrome and this is also caused by Staphylococcus aureus so we've already discussed about various hair follicle infections that Staphylococcus aureus can cause now I'm gonna talk to you about a specific disease here called scalded skin syndrome this is caused by Staphylococcus aureus now this infection typically begins at or near the mouth of the patient and it quickly spreads throughout the entire body okay symptoms are reddened skin skin peels off etc etc all right so here's a pathogenesis right the disease is caused by an a/b toxin that is released by the bacteria that's growing on the skin you know about a B toxins because we discussed toxins already okay so then what happens is that the the individual will have these large blisters that will be produced due to this infection with clear fluid within a couple of days the outer layers of the skin know this usually happens in children more specifically in newborns within a couple of days the affected outer layers of the child skin off us of the skin peels off in sheets almost as if they have been dipped in boiling water this is a very serious skin infection very serious infection and as you can imagine the seriousness of the disease is really going to be dehydration okay among other things for example invading bacteria through the open skin if you look at this child it looks the child looks like like they have been burned right so the body fluid loss you have body fluid loss as the skin peels off so even if you just touch the child the skin just peels off in sheets it's a terrible terrible infection causative agent as I mentioned 200 that was stuff that's wound infection it's not yet I'm not ready so this usually strikes children under the age of five particularly infants and if an infant has this in a nursery it's not uncommon that it spreads throughout the entire nursery now why does this happen well because these babies lack immunity right and healing takes about a couple of weeks this condition and characteristic that you see here that's red and inflamed and the skin peels off in sheets it can also be a characteristic of the later stages of toxic shock syndrome interestingly enough all right another infection that is caused by Staphylococcus aureus is that referred to as staphylococcal wound infection so how does this happen you get the Staphylococcus aureus in the wrong place of your wound okay maybe you've had surgery and you didn't take care of yourself and inflammation will ensue swelling redness pain etc one of the characteristics of Staphylococcus aureus is its ability to produce an enzyme called coagulase coagulase is an enzyme that coagulates or clots fibrin in the blood well what is fibrin fibrin a protein that's involved in clotting blood so that is a pathogenic that is a variance factor or it is another virial instructor that Staphylococcus aureus possesses also we know that Staphylococcus aureus has protein a well what does protein a doe do do you remember what protein a does protein a is going to disrupt opsonization how protein a disrupts opsonization by binding to the antibody in the wrong orientation right yeah so we know that protein a coats the bacteria in the host protein and we also know that Staphylococcus aureus produces other toxins that are going to lead to inflammation in other words this organism has many structures that allow the pathogen to survive in the body the epidemiology well we know that many individuals can be carriers so nasal carriers or you can get this this through fomites what are four mites inanimate objects if you are unlucky and you get this staphylococcal wound infection there are treatments there are antibiotics but once again remember that many of these staphylococcal oreal aureus strains are resistant to many antibiotics right so how do you prevent this wound cleanliness is going to be a huge factor you see here we have two different wounds in fact this one you can see that the sutures just opened up and you can see that the tissue surrounding the area that was sutured is actually dead so in order to researcher this you'd have to cut around to get the fleshy material again and then suture it back up here we see that this this incision here is closed but it's starting to drain that is not a good sign that means that there is an infection it may not open like this one on the right but it's not looking good so action needs to be taken in that case right so why is Staphylococcus aureus so virulent well just look at the number of variance factors that this organism has it can has it has the ability for a capsule production right so it has a capsule it can produce coagulase it has all these different enzymes that it can produce that are virulence factors hyaluronidase which helps evade phagocytosis strep to license is it's another one so it has many or these license here that lies white blood cells or red blood cells right so it does produce many different variance factors that afford this organism the ability to continue to grow establish disease and cause a lot of damage protein a toxic shock syndrome many different virulence factors alright so we've doubt lined three different types of infections caused by Staphylococcus aureus okay step locus aureus not a good microorganism to be infected with there is another microorganism that I want to talk to you about and that is going to be streptococcus pyogenes okay now streptococcus pyogenes has many different variants factors as well and it causes different types of infections so the first infection or disease that we're going to talk about is called streptococcal impetigo now impetigo is caused by streptococcus pyogenes group a beta hemolytic Oh what is beta hemolytic mean do you remember well we'll discuss this soon in lecture okay okay so let's talk about impetigo this is a skin infection that mainly affects infants and children usually the microorganism will enter through some sort of minor a break maybe even an insect bite okay now this microorganism also has many structures that allows a pathogen to survive in the body symptoms pyoderma you'll get these blisters on the skin that release pus and they form a dry crust and I'll show you what the what that looks like okay as I mentioned it has many variants factors that allows it to thrive and cause disease including hyaluronidase and etc etc right whew that's not similar to step the caucus doesn't it yes it does so let's talk a little bit about how this looks like here we see ok streptococcal Petitte I go it starts as a red sore that's usually how it starts it starts as a red sore at the site of infection and it quickly ruptures and it oozes for a few days and it forms this yellowish brown crust that you see here that almost looks like brown sugar kind of gross right it's very itchy ok very itchy or it can't be very itchy the disease is highly contagious so scratching and touching the sore can spread to other parts of the body which oftentimes children will do but it can also spread to other people okay so that is how this infection or this disease looks like not a good thing to have not a very pretty looking either right so I pity me ology is going to be contact transmission from carriers or fomites how do you prevent this what wound cleanliness making sure that if you do have a sore that you keep it clean you take proper care and maybe some topical antibiotics right so treatment antibiotics penicillin or erythromycin is if it gets really bad then obviously you would have to be on a oral antibiotics rather than just the topical when you first see the little sign of a possible infection all right moving on another disease that's costs or infection that's caused by streptococcus pyogenes is going to be that which is referred to as flesh-eating streptococcal infection oh well that doesn't sound good hmm let's talk about this this is going to be a rare infection where streptococcus enters the body through again a break in the skin and once it enters the body it begins to secrete enzymes and the toxins that destroy the tissue this bacteria will specifically produce a toxin called exotoxin a exotoxin a acts as a super antigen and it causes the immune system to contribute to the damage this is referred to as necrotizing faciitis or it's also known as necrotizing faciitis and it also involves toxemia well what is toxemia do you remember what toxemia is toxin in the blood as a result failure of many organs and death is not uncommon in fact it has about a 50% mortality rate not a good thing epidemiology sporadic cases predisposing factors is not a good thing for individuals that already have these conditions such as diabetes cancers you know anything that immuno suppresses you is gonna make you more at risk with pretty much any of these infections treatments surgery and penicillin there is no way to prevent it I mean you just have to be careful if you notice something take care of it right away but it's really just an unfortunate situation this does happen though there's about 15,000 cases a year in the US again mortality rate is about 50% and these are the various conditions that it can cause the terms that we went over at the beginning cellulitis Myositis necrotizing faciitis now at the beginning I mentioned to you flesh-eating hmm the bacteria is not really eating the flesh right but the toxins of the bacteria produces destroys the tissues so quickly that sometimes the doctors or the physicians when they're doing surgery they cannot remove the tissue at the same speed that the bacteria is actually destroying the tissue which is why often times amputation is the safest and fastest way to stop this bacterial infection because as you can see it's detrimental the what it causes it's just it's an awful infection okay so why does this bacteria cause such terrible infections well if you take a look at the list of the various variance factors associated with this bacteria there are many right there are many variants factors kind of like Staphylococcus a little bit different or cephalic Rawkus aureus to be specific you know it has some similarities to Staphylococcus aureus but it also has some of its own hmm so these are the various virulence factors associated with streptococcus pyogenes it has many and these are the effects of the various virulence factors and you can see that there are some similarities like him a license which lies red blood cells we find that in both staff cox aureus and streptococcus pyogenes for example right yeah so there are many different other skin infections that we will be discussing in the next lecture this concludes Part A of lecture 19