MM Midterm 1 - Part 1 (Notes from 08/19-09/11)

What’s medical microbiology?

A class that examines microbials that are capable of causing human disease and the interactions between these organisms and their hosts

What’s an infection?

An establishment and multiplication of a microorganism within a host

What’s a disease?

A disruption of normal host function resulting from infection

Explain the importance of germ theory to modern medicine

Germ theory is what allowed doctors to discover the cause of diseases or death that “spontaneously appeared” are in fact small microbes. Saving lives and resulting in much more sanitary medical practice

What are Koch’s postulates?

1. The microorganism should be found in organisms suffering from the disease

2. The microorganism should be isolated and grown in pure culture (solution)

3. The cultured microorganism should cause the disease when introduced into a susceptible host

4. The same organism should be re-isolated from the experimentally infected host

What’s a short way to describe Koch’s postulates?

Association → Isolation → Causation → Re-isolation

Why can’t every pathogen satisfy Koch’s postulates?

1. Some microorganisms cannot be easily cultured

2. Some infected people don’t become sick

3. Ethical limitations on humans

Outside of Koch’s postulates, today we use ___, culture, microscopy, ___, experimental models and ____.

Epidemiology, molecular detection and immunology

Bacteria are tiny ____ that lack a true nucleus

single-celled microorganisms

Viruses are pieces of ___ with a protein wrapper

nucleic acid

What’s the other definition of a virus?

An obligate intracellular parasite

Fungi are ___ that have chitin cell walls

eukaryotic organisms

Protozoa are ___ that possess a nucleus, organelles, 80S ribosomes and a complex metabolism

unicellular eukaryotic organisms

Helminths are ____ parasitic worms.

multicellular eukaryotic

What structures do bacteria possess?

Peptidoglycan, cell membrane(LPS), 70S ribosome, plasmids, capsule, fimbriae pili, flagella and endospore

What are the unique structures of a virus?

Genome, capsid, envelope and surface proteins

Why do differences in microbial biology influence treatment?

The differences are what could be used as a target unique to the pathogen in order to not harm the host

Why do viruses require host cells for replication?

They have no ribosomes, enzymes and other energy producing pathways to make proteins in order to copy their genetic material independently

What gram is thick peptidoglycan?

Gram - positive

What is virulence?

Traits of pathogens that cause harm

What was semmelweis’ intervention?

The demonstration that something transmissible was causing disease before microorganisms were established

Pasteurs and spontaneous generation:

He discovered that boiling kills microorganisms and that you need to keep the lid on so growth will stop

Microorganisms with ___ make phagocytosis difficult to do

capsules

What’s tropism?

Certain viruses only infecting certain cells/ areas

Why can’t every virus infect every cell in the human body?

The appropriate receptor must be present

What is in the fungal cell wall?

Ergosterol

T or F: Protozoans only have one way of movement

False; they have several ways to move (flagella, cilia, pseudopodia)

What are the three major groups of helminths?

Nematodes - roundworms

Cestodes - tape worms

Trematodes - flukes (like a flat worm)

What’s an intermediate host?

a host that’s needed for parasites (helminths) to complete a life stage, reproduction doesn’t happen here

Bacterial growth is the increase in the ____, not necessarily increase in __.

number of cells/size

How do bacteria grow?

Through binary fission

What are the phases of the bacterial growth curve?

1. Lag phase - where there is no growth, just adjustment to environment

2. Log/exponential phase - rapid division occurs, high metabolic activity and the population increases exponentially

3. Stationary phase - nutrients and oxygen are depleted, waste accumulates and the pH changes

4. Death phase - toxic accumulation occurs and cell lysis

In the stationary phase ___ is about equal to the number of cells dying

number of cells produced

Does the death phase mean every bacterium dies?

No, bacterial persistence is a thing

What types of bacterium require oxygen to survive?

Obligate aerobes

____ can grow with or without oxygen

Facultative anaerobes

T or F: Oxygen is harmful to obligate anaerobes

True

How does the bacterial growth phase relate to antimicrobial susecptibility?

Penicillin would be more effective against a bacteria in it’s rapid division growth phase than stationary, lag or death

What are planktonic bacteria?

Bacteria that are close together but not connected, you can see their individual rod structures

What is biofilm?

Bacteria binded together with a protective extracellular matrix

T or F: Every bacterium can form a biofilm

False

How can bacteria acquire new characteristics?

Mutation and through horizontal transfer

Mutation is ___.

a change in the nucleotide sequence

What’s the horizontal transfer in reference to bacteria?

Conjugation, transformation and transduction

T or F: Antibiotics cause bacteria to decide to become resistant

False, antibiotics select resistant organisms when majority bacteria die but not all of them

What’s transformation?

Bacteria bringing in naked DNA that’s present in the environment

What’s conjugation?

two bacteria transferring each others nucleic acid (often transferring plasmids)

____ is when viruses infect bacteria using a bacteriophage while keeping the bacteria alive

Transduction

The ___ is a virus that infects bacteria while carrying bacterial DNA

bacteriophage

Do bacteriophages infect humans?

No

R plasmids are __.

resistant plasmids

Why are R plasmids important medically?

They are unaffected by antibiotics

__ is the most common stain for bacteria but it is not the only one

Gram stain

What does doing a gram stain on bacteria show us?

Gram type and shape

Cultures provide the ____ organism, phenotypic identification, _____ and additional characteristics

viable/antimicrobial susceptibility testing

Why culture organisms if PCR (polymerase chain reaction) exists?

PCR can’t determine if the pathogen is alive or not, it’s phenotype or its antimicrobial susceptibility

What do we usually use PCR for?

Viruses or intracellular bacteria

What are the human microbiota?

Bacteria, fungi, viruses, archaea and protozoa

____ = the organisms themselves

Microbiota

Microbiome =

the collective genetic material and ecological environment of microbiota

What’s colonization?

establishment and persistence of a microorganism at a body site without necessarily causing disease

What are some common colonizations on the body?

Staphlococcus epidermis → skin

E. coli → large intestine

Candida spp → mucosal surfaces

____ is what determines if a microbe is gonna cause a disease

Location

What are three ways microbiota can benefit us?

1. Metabolically - nutrient processing and production of some metabolites/vitamins

2. Immune - influences immune development and function

3. Protective - prevents colonization by invading pathogens

____ is the ability for resident microbes to limit establishment or expansion of potential pathogens

Colonization resistance