we started this chapter talking about the difference between being pathogenic and being virulent so pathogenic has to do with the capacity to cause disease virulence has to do with how intense is that disease so how dangerous is this microb so in this section we're going to talk about these virulence factors that make an organism virulent so a variance Factor these can be either structural or physiological things that help the microb cause disease so not only do I think about them being able to cause disease but they have to be able to survive because if they can survive our defenses that means they're going to be more dangerous so some variance factors are things like adhesion pilli so these are almost like sticky cups on the microb that allows them to stick to cells if they can stick to cells then they can be dangerous to cells enzymes that break down host defenses we'll talk about a few enzymes and toxins that are going to disrupt homeostasis how is it that bacteria can get inside the host and cause damage well the easiest way as if our Fortress Is penetrated our skin so if you get a break in your skin in that's going to be an easy entry point so for example my cellulitis from that bug bite things were able to enter the easiest way for bacteria to get into our body is through mucus membranes mucus membranes are going to basically line all of those orifices to the outside world and that's going to be an in for these bacteria microbes can also they can be transmitted sexually through that direct contact they can also be inhaled and they can also be transferred by way of fomites and fomites are in adamant objects so think about all of the many things that you touch throughout the day a patient could possibly touch in their um hospital room so we were actually testing fomites in our ubiquity lab so when we were testing the bottom of our shoe that would be a fomite the door knob handle that would be a fomite our phones that's another fomite so that's a way that um microbes can actually be transmitted so imagine that um somebody's leaving the classroom and they sneeze and they rub their nose and then they touch the door handle now that germ is on the door handle you are the next one out and you touch that door handle and then you scratch your eye now that's going to be an easy entry for that pathogen this is also the reason why I go around um and try to open up doors with my sleeves instead of my hands um because you never know what's going to be on those those fomites so that's something that we tested early on in our ubiquity lab so we're going to get into some of these specific ific virulence factors so as I was saying before if bacteria can stick to things if they can adhere to cells then that's going to be a problem they can cause disease so bacteria can have proteins adhesin that are on these attachment pilly and again I kind of think of like little sucky cups that like stick to things and that's going to allow them to stick to cells we talked about capsules so capsu are really thick layer of a glyx that makes them sticky it makes them hard to kill so that's one reason why it's a variance factor and it also allows them to stick to cells adhesin can also block phagocytosis so it can block these immune cells from gobbling them up so these adhesin can actually be variance factors so once a back bacteria is in it's going to start to take hold and this is what we call colonization so they're going to become invasive and they're going to start to get inside host tissues this is going to make it really difficult to actually get rid of them so we're going to talk about some enzymes that are actually variance factors anytime that you see a word that ends in as that means it's an enzyme enzymes are usually named for the substrate they work on so anytime that you see a term and ends an ASE it's a good bet that it's an enzyme so in order to keep our cells together to get our tissue to be cohesive there's something called hyaluronic acid which is actually the glue that kind of holds tissue together you've probably seen some advertisements for some skin cream um that promote that they have hyaluronic acid um in their product so you've probably actually seen this advertised on TV well that's the glue that helps to kind of hold our tissues together there's a bacteria strepto cacus which actually makes hyon day so this is an enzyme that dissolves the glue that holds that tissue together in fact we call hyaluronidase spreading Factor so it can separate those cells so that it can get deeper and deeper into the tissue this is a problem because it's going to be really difficult to try to get rid of them catales is something that we look at in lab so catalase is something that staff bacteria make that actually breaks down damaging oxidizing agents the way that we can test to see if an organism has catalase is that we add some hydrogen peroxide to a slide then we take our bacteria and then we make a little suspension if we see bubbles that means that that bacteria has that enzyme catalase and it's breaking down that hydrogen peroxide into water and oxygen and the bubbles is actually the release of the oxygen now normally these oxidizing agents like hydrogen peroxide that we might see and like peroxisomes or damaging oxidizing agents that could kill a bacteria normally this would be a problem for the bacteria but if they have this enzyme they can break it down into something harmless Like Oxygen and water and it's going to be able to survive so again if it can survive that means it's going to be a variance factor a another enzyme that we look at that storus makes is coagulase coagulase is used to clot the blood so what it does is this enzyme takes fibrinogen and converts it to fibrin so this is the normal blood clotting mechanism fibrin is kind of like the internal threads that plug up a hole that plug up our you know if we got a cut to stop from bleeding so what this bacteria does it releases this enzyme it converts that fibrinogen which is in the plasma to fibrin and now it's forming this blood clot this blood clot is acting like a little cocoon where now it can actually hide in this clot in this cocoon so that the immune system and the immune cells can't find it now some bacteria have streptokinase this enzyme actually dissolves clots so if it wants to break out and then it can go and infect other cells it can release this enzyme and then it sort of set free to go infect other cells you might have actually heard streptokinase used to treat heart attack patients because it can actually dissolve those clots some bacteria are very sneaky like retus and chlamidia where they can um grow and divide in a Cell um and so that makes it difficult for the immune system to find them so any way that this bacteria can stick to a cell cause disease survive that means it's going to be dangerous it's going to be virulent and that's that's why we call these falance factors so here are some pictures so if you're a visual person like I am and you like to kind of see these things in action the first picture is hyon day so this is what they call spreading Factor remember hyaluronic acid is like the glue that holds those cells the tissues together when this bacteria releases this enzyme it breaks down the glue and now in that third picture you can see that bacteria is getting deeper and deeper into the the tissues harder to find harder to kill the bottom picture this is coagulase storus releases coagulase forms a clot and then it can hide in this little cocoon this blood clot so the immune cells can't find it some bacteria when they are in a clot they can actually release streptokinase and that allows them to break free and now they can actually go out and infect cells there are also toxins that can cause some issues a toxin is basically something that's poisonous to another organism so when we talk about toxins with bacteria there's two types we talk about exotoxins and endotoxins exotoxins these are going to be strong soluble toxins that are secreted into the host tissue mostly with our exotoxins we see this with with gr positive organisms maybe a few gram negative bacteria but it's mostly gr positive organisms we're actually going to see some of these exotoxins in lab and one of those example are enzymes which are holins hcin break open red blood cells so not only is that damaging the cells of the host but when these bacteria break open the red blood cells they can actually gobble up the nutrients and they can actually get the oxygen and use it obviously if they destroy our red blood cells that's going to be an issue for us lucos cidon these are also exotoxins these destroy white blood cells so we will be talking about nutrifil and macras um coming up in the immune chapters they will gobble up by way of Phagocytosis the pathogens so if the pathogen is releasing this exotoxin glucos cidon it will outright kill these um phagocytes glucos statins will stop these white blood cells from engulfing the bacteria so basically stop them in their tracts so exotoxins we see with gram positive organisms endotoxins we see with gram negative bacteria so these are weak toxins unless they are in very large quantities and we see this with gram negative bacteria because if you remember the cell wall of gram negative bacteria it's that peptidoglycan sandwich where we have the inner membrane a thin layer of peptidoglycan and then the outer membrane that outer membrane has lipopolysaccharide when that lipopolysaccharide gets released it acts as an endotoxin so if we have a patient and they're treated with antibiotics and we have a massive gram negative kill they can actually release a lot of this lipopolysaccharide and cause endotoxic shock which we can sometimes see with the elderly so this can cause severe fever low blood pressure tissue damage um it's a bad situation so with endotoxins those are really are found in our gram negative bacteria so I mentioned these holins and H are enzymes that are going to break down the red blood cells so what we're going to be observing in lab are the different types of homolysis so Alpha is partial breakdown of hemoglobin and when we actually grow the organisms on a blood augur plate it will start to partially break it down and we will actually get the release and we'll end up with this greenish Hue so if you have ever gotten a bruise and you know how the bruise turns all those weird colors that really has to do with that breakdown of hemoglobin so there are some bacteria that will partially break this down and will exhibit Alpha hemolysis so hemolysis is not a good thing because it's going to destroy our red blood cells however we can actually use this as an advantage in lab to help us to identify organisms so if we were to grow an organism on a blood auger plate and it exhibits Alpha hemolysis that's going to give us a clue as to what bacteria that is so for example strep pneumonia exhibits Alpha hemolysis Beta hemolysis is complete breakdown of hemoglobin and it's going to be completely broken down it's going to look almost like a yellowish clear translucent plate where we would be able to see through that blood auger plate and our organism Street pyogenes actually exhibits beta hemolysis gamma hemolysis is lack of hemolysis so we would just see the growth on the blood augur plate as these white colonies that hemoglobin would not be destroyed so it would remain that dark red color so a couple of things to help you kind of keep straight alpha beta and gamma so Alpha has a p in it partial begins with P you know I like my letter associations I think of a b c so that's how I remember that beta is complete homolysis and then gamma it's just lack of homolysis we just see the organism um growing as it normally would so I will show you a picture of the different types of homolysis I will tell you that it is much different to see and lab beta homolysis you can see on the left that's complete hemolysis so if you were to hold up this plate after this organism is growing on it you would be able to see through it so it will have like a yellow tinge to it but it's almost translucent if you were to hold up a plate where there was an organism exhibiting Alpha homolysis it would have sort of a greenish Q you wouldn't be able to see completely through the plate it's not completely translucent and then gamma homolysis it's hard to tell in this picture but we would see these white colonies growing on the surface and we would not see um any kind of seeth throughness at all of the plate it would still be that dark red color so we in lab are going to be getting familiar with recognizing the types of hemolysis as well as identifying using this to help us identify different organisms and with hemolysis we mostly see this with our strep organisms