 Hey everybody, Dr. O. In this video I want to do a quick comparison of the two types of toxins produced by bacteria. We have endotoxins and exotoxins. I will dive into different types of exotoxins in a separate video. So hopefully you remember when we learned about bacterial anatomy that endotoxins are actually built into the lipid outer membrane of gram-negative bacteria. So that's why endotoxins are going to be produced by your gram-negative bacteria. At least now there are some gram-negatives that produce these, but I like to say when you hear hooves think horses, the gram-positive bacteria produce exotoxins. So just think endotoxins, think gram-negative, exotoxins think gram-positive. That's almost always true. The composition with gram-negative bacteria, every gram-negative bacteria produces the same endotoxin. It's called lipid A. So again it's part of that lipopolysaccharide membrane. Exotoxins are protein products which means they are specific to each individual organism. They each turn out their own proteins, it has its own structure and its own function. So these are going to be unique to different organisms, whereas all gram-negative bacteria make the same endotoxin. Let's see the effect on the host. So gram-negatives because there is no specificity, it's very generalized so it's going to cause fever, inflammation, these types of things, real generalized symptoms throughout the body. I think this is a very common source of inflammation, even in seemingly healthy people. The exotoxins produced by gram-positive, they are going to be specific. So we'll have different types. There are super antigen exotoxins that cause this massive inflammatory and immune response that can be fatal. You've got the cells that have membrane disrupting toxins, different types of toxins. So it's going to be specific depending on the toxin, depending on the organism. Next heat stability, this is a big deal especially with foodborne illness and making sure you're removing toxins. The endotoxins are quite a bit more stable in heat because they're lipid based so they can survive at higher temperatures, whereas exotoxins because their proteins, the toxin proteins can be denatured or unraveled, generally at pretty low temperatures so like it says here most are heat labile, most of them are killed at temperatures around 41 degrees Celsius or about 105, 106 degrees Fahrenheit. There is one huge exception though and that is Staphylococcal Enterotoxin. So that is one that can still cause foodborne illness even in food that's been cooked above that temperature. I always use that as an example of how you can properly prepare food twice and still get sick, properly prepare it, cook it to the appropriate temperature, then you let it sit out at a family reunion or something and it sits out too long and these Staphylococcal organisms are there and they grow and produce toxins. So in the next day or whenever you reheat these leftovers and you cook them to the appropriate temperature which will kill the staff organisms but this toxin is heat stable so the toxin would still be there. So you cook the food twice, cooked at wealth twice, still got sick though because that food sat out in the quote unquote danger zone for too long. So Staphylococcal Enterotoxin is a really important example of an exotoxin that is heat stable. Based on here we see the LD50 that'd be the lethal dose of this toxin for 50% of the population. The LD50 for endotoxins is very high whereas it's very low for most of your exotoxin. So the LD50 for the lipid A endotoxin is .24 milligrams per kilogram. So compare that to the most potent exotoxin that I can think of the botulinum toxin which causes botulism has a lethal dose 50 of .000001 milligrams per kilograms that makes it 240,000 times more lethal than the bacterial endotoxin. Alright so that is most of the really important stuff just a couple more things I want to add here. You've got exotoxins, now this is good news, exotoxin can be converted into toxoids which means that you can you know toxoids are vaccines against toxins and exotoxins can also be neutralized by antitoxins. So like again if you get your tetanus shot the toxoid that will protect you from the tetanus toxin but then also you can get a tetanus antitoxin if you know if you get to it in time. So exotoxins as you can see the lethal dose is a lot lower they can definitely be more dangerous but thankfully we have these types of treatments vaccines and treatments. The other other really important thing to note here is that endotoxins are the ones that cause fever I've already mentioned it before but they they do cause fever I'll cover the mechanism and how they cause fever later basically triggers your own immune system to do it and we'll talk about why that's important. So just a couple of examples before I leave you endotoxins think of like typhoid fever meningococcal meningitis urinary tract infections those would be common conditions where endotoxins play a role exotoxins I've already mentioned tetanus and then gas can green would be a good example and so would diphtheria alright so that's everything you're gonna need to know about endotoxins and exotoxins the two types of toxins produced by bacteria I hope this helped have a wonderful day be blessed.