in this video, we're going to begin our lesson on cokes postulates. And so Robert Coke was actually a German physician of the late 1800s who designed a set of postulates or a set of criteria that are used to identify if a particular microbe causes a specific disease. And so, using his postulates, robert coke was able to discover that anthrax which is a specific disease and cattle and humans is actually caused by the bacterium, bacillus anthracis. And so cokes postulates can be defined as a set of criteria that are used to determine if a particular microbe causes a particular disease. And so if we take a look at this image down below, which you'll notice is we are showing you robert coke over here and notice robert coke is saying, hey, my four postulates can show us what pathogen is causing your disease. And notice that robert coke is saying that to dr clutch prep over here and notice that dr clutch prep is sweating and has a fever and is not fearing very feeling very well. And so he is appreciative that robert coat can use his postulates to determine if a microbe is causing his disease. And so, in our next lesson video, we'll be able to talk more details about robert Koch's postulates. So I'll see you all in that video

in this video, we're going to talk more details about robert Koch's postulates. And so it turns out that there are actually four postulates that robert coke used to link a specific microbe to a specific disease. And so notice down below, we're showing you an image of all four of these postulates that are used to determine once again if a specific microbe causes a specific disease. And so the very first partial it states that the microbe must be present in every single case of the disease. And so it can't be the case that the disease is present in a host. But the microbe is not if that's the case, then the microbe probably doesn't cause the disease. And so notice over here what we're showing you is a mouse that is a diseased mouse. And so it's not looking very good. Over here. Now, the second postulate states that the microbe must be isolated from the diseased host and it must be grown in a pure culture. And recall that a pure culture is a culture that consists of only one single species and that would be the specific microbe that was isolated from the host. And so notice over here, we're showing you a syringe going into the diseased host here, and the syringes extracting the specific microbe. And that microbe and the syringe is being grown on a Petri dish, which we refer to as a pure culture because it only contains the one specific microbe that was isolated from the diseased host. Now, the third postulate states that the same exact disease must occur when the pure culture that was isolated from the diseased host is introduced into another susceptible host. And so notice. Over here we're taking the pure culture and the pure culture is being introduced into another mouse, another susceptible host. And so when that happens, this mouse must develop the same exact disease. And so the fourth postulate states that the microbe must be experimentally isolated or must be isolated from the experimentally infected host. And so what that means is that from this mouse that developed the disease, a syringe must be able to go into that mouse and extract the same exact microbe. And so these are the four postulates uh that makeup cokes postulates and that must be met in order to conclude that a specific microbe causes a specific disease. And so if these postulates cannot be met, then the assumption is that the microbe does not cause this specific disease. Um however, there are some limitations. Two cokes postulates that we will talk about more as we move forward in our course. But for now this here concludes our discussion on coast postulates and we'll get to learn more as we move forward. So, I'll see you all in our next video

So while cokes postulates serve an important role in determining the cause of disease. There are limitations to coax postulates. And so in this video we're going to be focusing on some of the limitations two cokes postulates. And so if you take a look at our image down below, notice that towards the top of our image, what we have is cokes postulates as we discussed them in our last lesson video and then notice down below, we have some of the limitations. Two cokes postulates. And so recall that the second of cokes postulates states that a microbe must be isolated from the disease host and grown and pure culture. Now, a limitation for this particular postulate is that unfortunately not all pathogenic microbes can actually grow on laboratory media and so we are not able to grow all pathogenic microbes in a pure culture. And so that's a huge limitation because for example, obligate intracellular pathogens, they cannot be grown in pure culture because they can only grow in the presence of a host cell. And there are many other organisms as well that again, we do not know exactly how to grow them in the lab because we don't know exactly what conditions they need in order to grow them in the lab. And so this is a limitation. Two cokes postulates, not all of the pathogenic microbes can be grown in pure culture. Now recall that the third of Kochs postulate states that the same exact disease must occur when the pure culture is introduced into a susceptible host. Now there are some limitations to this one as well because some pathogenic microbes actually do not cause disease and all infected individuals. And that's because not all test subjects are going to be susceptible to the disease. And so what you'll get is some individuals will have stronger immune systems, others will have weaker immune systems and that can lead to a symptomatic. Individuals, like for example, individuals that may have covid 19 may be asymptomatic and therefore may not display any signs or symptoms of the disease. Now, the fourth of cokes postulates recall states that the microbe must be isolated from the experimentally infected host. And there are limitations for this as well because there are plenty of ethical and safety concerns when it comes to human and animal testing and this can make the results unreliable, especially for human diseases. And so this here concludes our brief discussion about the limitations. Two cokes postulates, and we'll be able to get some practice applying these concepts as we move forward. So, I'll see you all in our next video