Foundations of Microbiology and Disease

From 1857 to 1914, we refer to this period as the golden age of microbiology. And the reason we do this is because this is when scientists began to understand that microbes, and I've got germs in parentheses, the microbes were actually what was responsible for causing disease. That was the transmission of microbes between persons that caused people to get sick. And... In some ways, this started with Louis Pasteur and his work with microbiology. He started really looking at spoiled food. In particular, you know, scientists, even though that we didn't understand that microbes were involved, people had been making wine and beer and bread for thousands of years. And, of course, that process of fermentation requires the presence of microorganisms like yeast, for example. Louis Pasteur actually... got involved with people who were making wine and he realized that it was the bacteria that were contaminating the wine that were producing acetic acid, which is vinegar in common terms, right? And so when that would happen, it would cause the wine to be spoiled. And what he did was he developed this process called fermentation, where they would treat the wine with heat for a and it would kill the bacteria. And so the wine wouldn't be spoiled. So he actually started his career sort of helping people in industry prevent spoilage of their product. He also worked with a silkworm disease as well that was devastating silkworms and tried to help that industry as well. So he got involved really kind of on the industrial side, not the medical side initially. But of course... When he became an expert at microbes, it allowed him to sort of extend our understanding, and he proposed this germ theory of disease, the idea that germs do more than ruin wine, right? They cause disease, and so he's responsible for that particular terminology. Pasteurization is kind of an interesting topic. You know, we now pasteurize milk. It prevents the transmission of bacteria like Campylobacter and bovine TB. and just E. coli 0157H7 that cause really horrific diseases in humans, particularly the E. coli and Campylobacter. But, you know, I always think it's kind of funny, you know, pasteurization didn't start to protect children from infectious disease. It started as a way to protect wine and save the profits of the winemakers. Another early sort of pioneer in the field of medicine and sanitation was a gentleman named Joseph Lister. You've probably heard of Listerine. Listerine doesn't contain phenol, or carbolic acid, which was the chemical that Joseph Lister used. But he knew about Pasteur's work and understood that Pasteur had shown that microbes are in the air. And he thought, well, you know, he's doing surgery on patients. And he introduced the idea of spritzing the surface of the patient and sort of the air around the surgical patient with carbolic acid. And this is really just the first example of the use of a chemical disinfectant. Of course, this is a horrible time to be a patient. There's a book called The Butchering Art. And if you want to read about surgery in this time, you can learn a lot about surgery reading The Butchering Art, but it won't make you feel good. I can guarantee you that. It's pretty gruesome. Here's a picture of a patient undergoing surgery. And you can see this is actually showing Lister's little phenol spritzer. this is. So they're going to spritz the patient with the chemical to help try to prevent infections. You can see these gentlemen, they don't look like they're sterile at all. They're wearing their street clothes. Yeah, pretty gruesome time to get. If you needed surgery, you probably might have been better off just kissing everyone goodbye because surgery wasn't the kind of thing that a lot of people survived. Some did, but a lot didn't. Another early microbiologist is Robert Koch. Robert Koch was born in 1843. He died in 1910. He's considered the father of modern bacteriology. And what he did that's unique in this group of individuals we're talking about was he came up with the idea that one bacteria can cause one disease. And he was actually able to identify specific causative agents. So for example, TB, tuberculosis, he identified Mycobacterium. tuberculosis as the individual bacteria. Those were coax bacillus is actually the name that they first gave to the rods that caused TB before they gave it its scientific name. He developed, he identified the cause of anthrax, he identified the cause of cholera, we refer to these as etiologic agents, and this work that he did to associate a single pathogen with a single disease we refer to the steps that one takes to do this work as Koch's postulates or Cox postulates. And these are still the gold standard of medical microbiology. So I want to take you through these postulates and explain to you how they work. On this slide, I have a list of the postulates from one to four and I don't usually read this because you can do that and of course these slides are available online for you to print out as well, but they're here for your reference. What I do want to do is show you a picture here and we'll go through the steps looking at this picture. Here we have a mouse and this mouse is either diseased or dead and microorganisms are isolated from this mouse and they're grown in pure culture on petri plates and we're going to learn how to do this in lab to take a mixture of biology and then isolate pure individual colonies of bacteria composed of just one species in a colony. So he did this and then he would look at these under the microscope and identify them and then he would take... confirmed it was just one bacteria. And he would take a little bit of this material then and he would inject it into a healthy mouse or healthy lab animal. And that lab animal, if they develop disease, he would look to see that the disease, of course, should be the same disease. It should look the same in terms of symptoms. But he would also then isolate organisms from the dead mouse or the newly diseased mouse. And he would grow those in pure culture, again, isolating individual species of bacteria and show that These bacteria isolated from the original mouse were the same as a new diseased animal, the bacteria isolated from that animal as well. So these are the steps to Koch's postulates, that you're able to actually isolate an organism from one animal and have that organism cause the same disease in a new animal that was previously healthy. So those are the major steps. And this is still used today in many different forms. There are some key exceptions to Koch's postulates because we know a lot more now. You know, it was really cutting-edge science to isolate a bacteria and show it caused disease in Koch's time. Nowadays, we sequence the entire genomes of all of these bacteria, and we understand that there are some exceptions. And even in Koch's time, some of these were a challenge. So there are many microorganisms, for example, that can't be grown in culture. A really... A good example of this is the organism Treponema palladium, which causes syphilis. And there have been lots of experiments on humans where people looked at syphilis and the disease it causes and the side effects in humans. But of course, that's completely unethical. And human experimentation with untreatable diseases, even with a treatable disease like syphilis, is certainly not something that we do to people without informed consent. Nowadays, we've done a lot of it in the past. Some diseases caused by different microorganisms have very similar symptoms. So for example, if you want to look at the common cold, it can be caused by a variety of different viruses, including coronaviruses and rhinoviruses. So it's really difficult to tell just by symptoms that it's truly the same organism that caused the disease. Some pathogens cause several different disease conditions. So for example, the organism that causes tuberculosis, mycobacterium tuberculosis, can cause disease in the lungs, but it can also cause miliary TB in the skin and the bones and internal organs. An organism called Streptococcus pyogenes can cause sore throats. It causes strep throat, actually. It causes scarlet fever. It can cause necrotizing fasciitis if it breaches the skin. So it can cause... Osteomyelitis, infection in the bone, it can cause a bunch of different things. And it causes childbed fever, which we're going to talk about in a little bit, which was a disease that another scientist was, who's in our early microbiology experts, was battling. All right, so there are some key exceptions to Koch's postulates. A moment ago, I referred to the idea that we now don't associate a single bacterium with the disease, but we go even deeper. We know the entire genetic material of individual bacteria. And there are many bacteria like E. coli, for example, where you have E. coli in your gut, and that E. coli actually helps you digest your food and it helps train your immune system as you're developing. It does a lot of good things for you. But there are strains of E. coli that cause disease, and it's because that the strains that are disease-causing usually have another gene that they've picked up from the environment or gotten from a virus, for example, that causes virulence. So E. coli O157H7 that causes food poisoning. You hear about spinach outbreaks. There was a romaine lettuce outbreak recently. It's really the same bacteria but with an extra gene, and it's that gene itself that causes. the disease phenotype that we see. And so we now refer to these as Koch's molecular postulates. And there's a link to these, a really nice article in Wikipedia, a link to these that you can access from the lecture slides. All right. So those are a very brief discussion of some of the golden era of microbiology and some of the key scientists who were innovators in that era. And we're going to move on and now talk a little bit about epidemiology and learn a little bit more about childhood fever. And, you know, one of the ways we look at diseases as they spread in society, one of the key ways that scientists study that.

And... In some ways, this started with Louis Pasteur and his work with microbiology. He started really looking at spoiled food.

In particular, you know, scientists, even though that we didn't understand that microbes were involved, people had been making wine and beer and bread for thousands of years. And, of course, that process of fermentation requires the presence of microorganisms like yeast, for example. Louis Pasteur actually...

got involved with people who were making wine and he realized that it was the bacteria that were contaminating the wine that were producing acetic acid, which is vinegar in common terms, right? And so when that would happen, it would cause the wine to be spoiled. And what he did was he developed this process called fermentation, where they would treat the wine with heat for a and it would kill the bacteria.

And so the wine wouldn't be spoiled. So he actually started his career sort of helping people in industry prevent spoilage of their product. He also worked with a silkworm disease as well that was devastating silkworms and tried to help that industry as well.

So he got involved really kind of on the industrial side, not the medical side initially. But of course... When he became an expert at microbes, it allowed him to sort of extend our understanding, and he proposed this germ theory of disease, the idea that germs do more than ruin wine, right? They cause disease, and so he's responsible for that particular terminology.

Pasteurization is kind of an interesting topic. You know, we now pasteurize milk. It prevents the transmission of bacteria like Campylobacter and bovine TB.

and just E. coli 0157H7 that cause really horrific diseases in humans, particularly the E. coli and Campylobacter. But, you know, I always think it's kind of funny, you know, pasteurization didn't start to protect children from infectious disease. It started as a way to protect wine and save the profits of the winemakers.

Another early sort of pioneer in the field of medicine and sanitation was a gentleman named Joseph Lister. You've probably heard of Listerine. Listerine doesn't contain phenol, or carbolic acid, which was the chemical that Joseph Lister used. But he knew about Pasteur's work and understood that Pasteur had shown that microbes are in the air.

And he thought, well, you know, he's doing surgery on patients. And he introduced the idea of spritzing the surface of the patient and sort of the air around the surgical patient with carbolic acid. And this is really just the first example of the use of a chemical disinfectant. Of course, this is a horrible time to be a patient. There's a book called The Butchering Art.

And if you want to read about surgery in this time, you can learn a lot about surgery reading The Butchering Art, but it won't make you feel good. I can guarantee you that. It's pretty gruesome. Here's a picture of a patient undergoing surgery.

And you can see this is actually showing Lister's little phenol spritzer. this is. So they're going to spritz the patient with the chemical to help try to prevent infections.

You can see these gentlemen, they don't look like they're sterile at all. They're wearing their street clothes. Yeah, pretty gruesome time to get.

If you needed surgery, you probably might have been better off just kissing everyone goodbye because surgery wasn't the kind of thing that a lot of people survived. Some did, but a lot didn't. Another early microbiologist is Robert Koch.

Robert Koch was born in 1843. He died in 1910. He's considered the father of modern bacteriology. And what he did that's unique in this group of individuals we're talking about was he came up with the idea that one bacteria can cause one disease. And he was actually able to identify specific causative agents. So for example, TB, tuberculosis, he identified Mycobacterium.

tuberculosis as the individual bacteria. Those were coax bacillus is actually the name that they first gave to the rods that caused TB before they gave it its scientific name. He developed, he identified the cause of anthrax, he identified the cause of cholera, we refer to these as etiologic agents, and this work that he did to associate a single pathogen with a single disease we refer to the steps that one takes to do this work as Koch's postulates or Cox postulates. And these are still the gold standard of medical microbiology. So I want to take you through these postulates and explain to you how they work.

On this slide, I have a list of the postulates from one to four and I don't usually read this because you can do that and of course these slides are available online for you to print out as well, but they're here for your reference. What I do want to do is show you a picture here and we'll go through the steps looking at this picture. Here we have a mouse and this mouse is either diseased or dead and microorganisms are isolated from this mouse and they're grown in pure culture on petri plates and we're going to learn how to do this in lab to take a mixture of biology and then isolate pure individual colonies of bacteria composed of just one species in a colony.

So he did this and then he would look at these under the microscope and identify them and then he would take... confirmed it was just one bacteria. And he would take a little bit of this material then and he would inject it into a healthy mouse or healthy lab animal. And that lab animal, if they develop disease, he would look to see that the disease, of course, should be the same disease. It should look the same in terms of symptoms.

But he would also then isolate organisms from the dead mouse or the newly diseased mouse. And he would grow those in pure culture, again, isolating individual species of bacteria and show that These bacteria isolated from the original mouse were the same as a new diseased animal, the bacteria isolated from that animal as well. So these are the steps to Koch's postulates, that you're able to actually isolate an organism from one animal and have that organism cause the same disease in a new animal that was previously healthy. So those are the major steps. And this is still used today in many different forms.

There are some key exceptions to Koch's postulates because we know a lot more now. You know, it was really cutting-edge science to isolate a bacteria and show it caused disease in Koch's time. Nowadays, we sequence the entire genomes of all of these bacteria, and we understand that there are some exceptions. And even in Koch's time, some of these were a challenge.

So there are many microorganisms, for example, that can't be grown in culture. A really... A good example of this is the organism Treponema palladium, which causes syphilis. And there have been lots of experiments on humans where people looked at syphilis and the disease it causes and the side effects in humans. But of course, that's completely unethical.

And human experimentation with untreatable diseases, even with a treatable disease like syphilis, is certainly not something that we do to people without informed consent. Nowadays, we've done a lot of it in the past. Some diseases caused by different microorganisms have very similar symptoms. So for example, if you want to look at the common cold, it can be caused by a variety of different viruses, including coronaviruses and rhinoviruses. So it's really difficult to tell just by symptoms that it's truly the same organism that caused the disease.

Some pathogens cause several different disease conditions. So for example, the organism that causes tuberculosis, mycobacterium tuberculosis, can cause disease in the lungs, but it can also cause miliary TB in the skin and the bones and internal organs. An organism called Streptococcus pyogenes can cause sore throats.

It causes strep throat, actually. It causes scarlet fever. It can cause necrotizing fasciitis if it breaches the skin. So it can cause...

Osteomyelitis, infection in the bone, it can cause a bunch of different things. And it causes childbed fever, which we're going to talk about in a little bit, which was a disease that another scientist was, who's in our early microbiology experts, was battling. All right, so there are some key exceptions to Koch's postulates. A moment ago, I referred to the idea that we now don't associate a single bacterium with the disease, but we go even deeper.

We know the entire genetic material of individual bacteria. And there are many bacteria like E. coli, for example, where you have E. coli in your gut, and that E. coli actually helps you digest your food and it helps train your immune system as you're developing.

It does a lot of good things for you. But there are strains of E. coli that cause disease, and it's because that the strains that are disease-causing usually have another gene that they've picked up from the environment or gotten from a virus, for example, that causes virulence.

So E. coli O157H7 that causes food poisoning. You hear about spinach outbreaks. There was a romaine lettuce outbreak recently. It's really the same bacteria but with an extra gene, and it's that gene itself that causes.

the disease phenotype that we see. And so we now refer to these as Koch's molecular postulates. And there's a link to these, a really nice article in Wikipedia, a link to these that you can access from the lecture slides.

All right. So those are a very brief discussion of some of the golden era of microbiology and some of the key scientists who were innovators in that era. And we're going to move on and now talk a little bit about epidemiology and learn a little bit more about childhood fever. And, you know, one of the ways we look at diseases as they spread in society, one of the key ways that scientists study that.

Transcript for:Foundations of Microbiology and Disease

Transcript for:
Foundations of Microbiology and Disease