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An Introduction to Microbiology 🧫 — Transcript

by Medicosis Perfectionalis · 3,128 words · 500 segments · language en · Watch on YouTube

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0:00What is going on beautiful people? This
0:02is Medicoases Perfectionalis where
0:04medicine makes perfect sense. Today
0:06we're starting a new playlist,
0:08microbiology. Step-by-step comprehensive
0:11discussion. So let's dive into the world
0:14of microscopic organisms. The field of
0:18microbiology deals with bacteria, fungi,
0:21and viruses. The field of medical
0:24parasitology cares about parasites. This
0:27microbiology playlist is for the
0:29detailed explanation. If you want quick
0:31reviews, check out my playlist called
0:34Picmonic Medicoases. So far this
0:36playlist has six microbiology videos. In
0:39the first video we talked about these
0:41bacteria, in the second one here, third
0:43one here, and fourth, plus five and six.
0:47If you want a quick review. Now let's
0:49get started. First of all, there is a
0:51big difference between microbiology and
0:54medical microbiology. Even the textbooks
0:57are different. This is intended more for
1:00biology teachers and biology students,
1:02but this is for medical students and
1:05doctors. The difference between them is
1:07so stark it's not even funny.
1:09Microbiology is like learning the
1:11Bernoulli equation. Medical microbiology
1:15on the other hand is like learning how
1:17to fly a freaking airplane. This
1:19playlist is dealing with medical
1:21microbiology. We're concerned with
1:23diseases here, not counting the freaking
1:26amino acids. Okay Medicoases, you will
1:28talk about medical microbiology. Will
1:30you talk about general or systemic?
1:32Unfortunately, most if not all
1:33professors start with general
1:35microbiology and they make their
1:37students hate themselves. They start by
1:40telling you how to culture bacteria
1:42without telling you why the flip would
1:44you culture them. They tell you how your
1:46immune system can protect you. Well,
1:48protect me from what? They tell you
1:50about the diagnostic tests before
1:53talking to you about the disease. This
1:55is just a stupid way of teaching.
1:56Medicoases going to start with systemic
1:58microbiology. The first order of
2:01business is to make you love bacteria,
2:03learn about disease, adore these
2:06stories, and after we finish talking
2:08about individual bacteria and the
2:11diseases caused by each one, then we can
2:13review the general and then I'll talk to
2:16you about the difference between
2:17endotoxin, exotoxin, all of this lovely
2:20stuff. So, besides the first few videos,
2:23I'll start going to staff aureus right
2:24away. But, Hamed the courses uh staff
2:26aureus can secrete enterotoxin, but you
2:29haven't told me what enterotoxin is.
2:31When we go to staff and you hear the
2:34word enterotoxin, it's my job to tell
2:36you what the enterotoxin is and what's
2:38the difference between endo- and
2:39exotoxin, all of this lovely stuff. But,
2:42you have to learn them in context, not
2:44in some ugly nonsensical abstract tables
2:47that make you have watery diarrhea, no
2:49pun intended. Microbiology is the study
2:52of small life, microscopic organisms.
2:56What microbes are we talking about?
2:57Bacteria, fungi, viruses, and parasites.
3:00Technically, parasites should not belong
3:03in the science of microbiology because
3:05micro means microscopic. Parasites could
3:08be huge. For example, the ascaris, the
3:11ancylostoma, these are very long worms.
3:15They are not microscopic by any stretch
3:17of the imagination. So, lumping them
3:19together here is just to make it easier
3:21for you. But, if you want the technical
3:23stuff, this belongs to a different
3:25science known as parasitology. Now,
3:27please pay attention because this is a
3:29very common source of confusion. There
3:32is a difference between a parasite that
3:34can affect humans causing these
3:36parasitic infestations and parasitic
3:40behavior. Cuz according to your woke
3:42biology professor, anything that lives
3:45in your body taking its resources is,
3:48{quote} a parasite, {unquote}. For
3:50example, the virus can hijack your
3:53nucleus. In this sense, the virus is a
3:56parasite. But, this is not the same
3:58thing as parasites from the perspective
4:00of medical parasitology,
4:03big difference. That's why this playlist
4:05is about medical microbiology.
4:07Therefore, we have bacteriology,
4:09fungology or mycology, virology, and
4:11parasitology. Nomenclature time.
4:14Kingdom, phylum, class, order, family,
4:16genus, species. When I write staff
4:18aureus like this, staff is the genus,
4:20aureus is the species. Do not write
4:24staff like this. You should write them
4:26in italics. Write staff like this. When
4:29the name is written in italics, it could
4:31be bacteria, fungi, or parasites.
4:34Viruses are not written in italics
4:37because the issue of viruses is a
4:39special situation. Viruses are not even
4:42living organisms. Ergo, when I write the
4:45word hemophilus influenzae like this, it
4:49has a totally different meaning from
4:50writing influenza like this. The first
4:54one is in italics. The second one is
4:56erect. It's not italics. The first one
4:59is a bacteria. The second one is a
5:01virus. Huge difference. Let's try an
5:03example. We start with the domain. In
5:06this case, it's a bacteria. After the
5:08domain, there's the kingdom. All right.
5:11After this, there's the phylum. We're
5:12talking about proteobacteria just as an
5:15example. After this, you go to the
5:17class. Are you alpha, beta, or gamma?
5:20Well, I'm gamma proteobacteria.
5:22All right. Now, there are many of these
5:25gamma proteobacteria. Which order? We
5:28are the enterobacteriales.
5:31And the word entero means gut, GI tract.
5:34And then, what's the family? We are the
5:36enterobacteriaceae.
5:39Wow. And what's your genus? Shigella.
5:42What's the species? sonnei. So,
5:44therefore, from a medical standpoint, we
5:47only care about the last two, the genus
5:49and the species. And therefore, my
5:51friend, unfortunately, you have shigella
5:54sonnei. What does that cause? Well,
5:56remember, it's part of the entero. So,
5:59it causes gastrointestinal symptoms.
6:02What do you mean? Usually diarrhea.
6:04Watery diarrhea or bloody diarrhea?
6:07Bloody diarrhea. I can write Shigella
6:09sonnei like this. I can write S. sonnei
6:12like this. The first one has to be
6:15capital. The second one is small. Upper
6:16case followed by the lower case. Upper
6:19case for the genus, lower case for the
6:21species. Or if the doctor doesn't know
6:23that it is sonnei per se, the doctor can
6:26write it as Shigella
6:28species like this. If we do not learn
6:31from history, we are doomed to repeat
6:34it, baby. Brief history of microbiology.
6:37First, Mr. Zacharias Janssen. First
6:40compound microscopy. I will give you
6:43nine times magnification as compared to
6:46your naked eye. Then, circa 1665, Robert
6:50Hooke. He saw cells under the microscope
6:54and he called these cells boxes because
6:57yeah, they live together like this and
7:00they look like a bunch of boxes. And
7:02then, my student, Antonie van
7:04Leeuwenhoek, saw the first living
7:07microorganisms.
7:09And but he did not call them
7:10microorganisms. He just called them
7:12animalcules. Oh, it's like an animal
7:14cell and a small one. It's like the
7:17difference between node and nodule, moon
7:20and moonlet, animal cell versus
7:22animalcules. Next, Monsieur Louis
7:25Pasteur said these are microorganisms
7:29and you can find them in the air.
7:31Really? Yeah, really. He also introduced
7:34the concept of pasteurization and
7:37inoculation. And then, John Tyndall and
7:40Ferdinand Cohn discovered that some
7:43microorganisms are heat resistant, which
7:46means you cannot kill them by simply
7:49cooking the food. Here is my man,
7:51Antonie van Leeuwenhoek. He saw a lumen
7:54in the center of the cell. This is what
7:56we now call the nucleus of the cell. And
7:59based on this, we classify organisms
8:01into prokaryotes
8:04and eukaryotes. The word caryo means
8:07karyon, which is the nucleus. I have a
8:10primitive nucleus versus I have the true
8:13nucleus. Bacteria are here. Humans are
8:17here. And then Robert discovered that
8:20you can get anthrax by ingesting
8:23contaminated animal meat. Also, you can
8:26inhale a spore from somewhere near the
8:29animal and you can get anthrax, too.
8:32This was followed by Joseph Lister and
8:35his antiseptic techniques. Oh, by the
8:38way, the famous mouthwash brand
8:40Listerine is named after Joseph Lister.
8:44I bet you the CEO of this company
8:47doesn't even know this. Man, these
8:49corporate shills. I'm just joking. Just
8:51joking. History is full of diseases that
8:53devastated individuals, communities,
8:56villages, whole countries, even an
8:58entire continent. Case in point,
9:00Yersinia pestis, which causes the black
9:03plague. Vibrio cholera, which causes
9:06cholera, watery diarrhea and vomiting.
9:09It is severe watery diarrhea. It can
9:12kill you from volume depletion. Many
9:15mothers unfortunately died during
9:17childbirth because of puerperal sepsis,
9:20which we now call peripartum sepsis. But
9:23this was about to change, at least
9:26partially, by a wonderful person known
9:28as Sir Alexander Fleming. He was sick
9:30and tired of being sick and tired and he
9:32said, "You know what? I'm going to close
9:34this lab. I'm going on vacation." He
9:36went on vacation, had great time with
9:38the wifey. But when he came back, he
9:40discovered something. He left the window
9:43open. Oh, some stuff entered from the
9:46window to his lab, landed on the culture
9:49of the bacteria, and he found that half
9:52of the dish is empty of bacteria. What?
9:56Where did the bacteria go? Well, maybe
9:58something killed it. Where did that come
10:00from? Oh, maybe it's from the window.
10:03What's the nature of that thing? It was
10:06a fungus known as Penicillium notatum.
10:10Therefore, he called this penicillin. He
10:13threw a wedge into the intergluteal
10:16cleft of history. There is history
10:18before penicillin, and there is history
10:21after penicillin. But say medical says
10:23he was just lucky. The harder I work,
10:25the luckier I get. Experience favors the
10:29mind prepared. Penicillium notatum has
10:33been around for millennia. Only
10:35Alexander Fleming picked up. In your
10:38practice, you will see two doctors who
10:41saw the same patient, took the same
10:43history, performed the same physical
10:44exam, but one doctor was able to arrive
10:48at the correct diagnosis, the other
10:50doofus just kept ordering test and
10:52reordering tests and reordering tests,
10:54even though it was the same patient.
10:56Experience favors the mind prepared. You
11:00know, if one of these old diseases like
11:03leprosy or the plague came and infected
11:06a patient and this patient came to the
11:08hospital, I can guarantee you almost all
11:11of the doctors will miss the diagnosis,
11:13except he who has his mind prepared. He
11:17who is ready for the extremely unlikely
11:20circumstances. How do we classify
11:22bacteria from a medical standpoint? By
11:24the Gram stain. The G has to be capital
11:27because this is the name of a scientist.
11:28At least have some respect for yourself.
11:30We have Gram positive bacteria and Gram
11:33negative bacteria. Gram positive appear
11:36as purple. Gram negative appear as pink
11:39under the microscope. And then the Gram
11:41positive are divided into two subtypes,
11:43same with the Gram negative. I could be
11:45purple and spherical. Now, I'm called a
11:48coccus. Or I could be purple and
11:50elongated like this, cigar-shaped. We
11:53call you a rod or a bacillus. Same thing
11:56with the Gram negative. So therefore, we
11:58have Gram positive cocci, Gram positive
12:01rods, Gram negative cocci, and Gram
12:03negative rods. Next, a beautiful love
12:06story in microbiology, the story of the
12:09wifey and her hubby. Both were
12:12microbiologists.
12:13Fanny suggested to her husband, "Hey
12:16doofus, why don't we use agar instead of
12:19gelatin as a medium to culture the
12:22bacterium?" Because her Walter tried
12:25everything as a medium for culture. He
12:28tried gelatin. He even tried freaking
12:30potato chips until his wife told him,
12:33"Try agar, it's more stable." And she
12:36made history. Experience favors the mind
12:40pre- pared. And as Dr. Thomas Sowell
12:42said, "It doesn't matter how smart you
12:44are until you stop and think." Some
12:47bacteria can make spores, others cannot
12:50make spores. Please be careful. Only the
12:54gram-positive are capable of making
12:57spores. Gram-negatives cannot make
13:00spores. Moreover, not only the
13:03gram-positives,
13:04only some of the gram-positive can make
13:07spores some of the time. So, if I ever
13:10hear you utter the following sentence,
13:12"This is a gram-negative spore-forming"
13:15Shut the French toast up. There is no
13:17such thing as a gram-negative
13:19spore-forming bacteria. If you're
13:21gram-negative, by definition, you cannot
13:23make a spore. There is another way of
13:25classifying things based on the position
13:29of a certain enzyme. For example,
13:31gram-positive cocci could be classified
13:32into staph or strep. Based on what?
13:35Well, do you have the catalase enzyme?
13:37"Yes," said the staph. "No," said the
13:40strep. What is the difference between
13:42cells and viruses? Well, cells, these
13:46are living cells. Viruses are not
13:48considered as living organisms. They are
13:50considered particles or non-living
13:52particles because they live on the edge
13:55between the living and the non-living.
13:57Viruses are weird. Cells can replicate
14:00by mitosis or binary fission. But, viral
14:02particles, nope, we're not doing this.
14:04Cells have cell membrane in every cell.
14:08Viruses, nope, I do not want your cell
14:10membrane. I might have an envelope. I
14:12might lack an envelope. Your cell has
14:15DNA and RNA, but viruses no, I choose
14:20one. I'm either a DNA virus or RNA
14:23virus, not both. Cells have many
14:26proteins. Viruses have few proteins.
14:29Cells have ribosomes. Viruses do not
14:32have ribosomes with only one exception.
14:35Cells have mitochondria in some cases,
14:38if you are a eukaryote, but prokaryotes
14:40do not have mitochondria. Therefore, do
14:43not tell me, "Oh, the electron transport
14:46chain was robust in the Staph aureus
14:48bacteria." What are you talking about?
14:50Why are you drowning in contradictions?
14:53If it's a bacteria, it's prokaryote, it
14:55does not have a mitochondria, ergo, no
14:58electron transport chain, no oxidative
15:01phosphorylation, no TCA or Krebs cycle.
15:05But viruses, no, we want nothing of your
15:09world. Cells have many enzymes. Don't
15:11forget enzymes are proteins. But viruses
15:13have few proteins and therefore few
15:15enzymes. Next, bacteria versus humans.
15:18Bacteria, prokaryotes. Humans,
15:21eukaryote. Do you have a cell wall? No,
15:24I do not have a cell wall, but bacteria
15:27do have a cell wall. Do you have a cell
15:30membrane? Sure, I do have a cell
15:31membrane. So does the bacterium. Cell
15:35membrane is the same as plasma membrane,
15:37the same as cytoplasmic membrane. Don't
15:40you ever forget that you lack cell
15:42walls, but bacteria do possess a cell
15:45wall. Why should I care? Because of the
15:48fact that you do not have a cell wall
15:50and the bacteria do have a cell wall,
15:53some medications, like the beta-lactam
15:55antibiotics, example, penicillin, can
15:59kill the bacteria without killing you.
16:01Why? Because these are cell wall
16:04synthesis inhibitors. They go to the
16:06bacteria and destroy her cell wall. They
16:09prevent the formation of her cell wall.
16:11The bacteria will die, but since you do
16:13not have a cell wall, penicillin will
16:16not kill you by inhibiting cell wall
16:19synthesis. It can kill a very, very,
16:21very, very minute percentage of patients
16:24because of an anaphylactic reaction, but
16:26that's a story for another time.
16:28Penicillin can kill the bacteria. Yes,
16:30but it cannot kill you because you do
16:33not have a cell wall, but the bacterium
16:36does. The bacteria are sneaky, man. They
16:38can evade your defense systems. They can
16:41evade your immunity. How come? Many
16:44mechanisms. For example, staff aureus
16:46has the enzyme known as coagulase. What
16:49does coagulase do? It's an enzyme, ace,
16:52that can coagulate. What does that mean?
16:54Convert fibrinogen, that's your
16:56fibrinogen, into fibrin in your own
16:59body. And now the bacteria is surrounded
17:02by fibers. These fibers will protect the
17:04bacteria from your own white blood
17:07cells, from your own immune system.
17:10Next, the presence of the coat known as
17:12glycocalyx, which literally means sugar
17:15coat or carbohydrate coat, prevents the
17:19bacteria from being eaten and
17:22phagocytosed by your phagocytic cells
17:25like the macrophage. In addition, some
17:27bacteria have a capsule. Encapsulated
17:31like the shin. What's the S?
17:33Streptococcus pneumoniae. What's the HI?
17:35Haemophilus influenzae. It's in italics,
17:38baby. It's a bacteria. That's not the
17:39influenza virus. Pay attention. And and
17:42Neisseria meningitidis. These are
17:45encapsulated organisms. Therefore, they
17:47can protect themselves from
17:48phagocytosis. Next, some bacteria such
17:52as Rickettsia can hide in your
17:54cytoplasm, but they will not hide inside
17:58the lysosome. They will hide outside the
18:01lysosome, away from the lysozymes in the
18:04lysosome. What does lyso mean? Lysis,
18:08destruction, breakdown. What does so
18:10mean? Soma means body. That's why we
18:13have the somatic nervous system. That's
18:16why the nerve cell, the neuron, had
18:19what? A cell body. It was called the
18:21soma, remember? That's the lysosome.
18:23Inside this lysosome, this body of
18:26destruction, what do we have inside?
18:28Destructive enzymes, lysozymes. What
18:31does zyme mean? It means enzyme. Pardon
18:34me, it means an active enzyme. Because
18:37if I want to write inactive enzyme, I
18:39will write zymogen,
18:41because it causes genesis to the enzyme.
18:45So, when you see zyme, it means active
18:47enzyme. Inside the lysosome, we have
18:48active enzymes. They can burn the
18:50bacteria. But the bacteria is sneaky.
18:52I'm going to hide outside. Moreover,
18:55bacteria like Bacillus anthracis can
18:58neutralize your lysozymes. You're so
19:01proud of your lysozymes. I'm going to
19:04make them inactive. #neutralization.
19:07In order for the lysosome to work, this
19:09lysosome, the ball of destruction, has
19:12to be combined with the target that we
19:15want to destroy. The lysosome has to
19:18bind to the phagosome. But some
19:20bacteria, such as Salmonella, prevent
19:22the fusion of the phagosome with the
19:24lysosome. You will not kill me. What's
19:27else? Tuberculosis has a virulent factor
19:31known as the cord factor. It also
19:33prevents the fusion of phagosome with
19:35lysosome. That's how you end up with
19:37tuberculosis. What's the name of the
19:39bacteria? Mycobacterium tuberculosis,
19:42formally known as TB bacilli. What's the
19:45name of the disease? Tuberculosis. In my
19:48lungs, it's called pulmonary
19:50tuberculosis. Last but not least, some
19:53bacteria can secrete leukocidins. I love
19:55the name. What does the IN mean? It
19:58means protein. The S is just for plural.
20:00Mostly, if you end in IN, you're a
20:02protein with few exceptions like
20:04heparin, for example. It ends in IN, but
20:07it's not a protein. Anyway, leuco means
20:09what? White. We're referring to your
20:12white blood cells, okay? What does cide
20:14mean? Cide means kill. E.g. homicide,
20:18suicide, infanticide. Leukocide is what?
20:22It's to destroy your own leukocytes. I
20:25will kill your immune cells. I will take
20:28you to the cleaners, said the tiny
20:30microscopic prokaryote. If you remember
20:33my video on tuberculosis, which was in
20:36my pulmonology playlist, we talked about
20:38the cord factor, which is the virulence
20:40factor. It's a protein. It impairs the
20:43fusion of phagosome with lysosome, and
20:46that's how the Mycobacterium
20:47tuberculosis invade your lungs. If you
20:50like this video, you will fall in love
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