Bacterial Pathogenesis I

Question 1

Single vs. Multiple Flagellum

Answer 1

A single flagellum at one end is called polar monotrichous while many flagella distributed around the bacterium is referred to as peritrichous.

Question 2

Gram Negative Components

Answer 2

Gram negative: cytosol is under the inner membrane; inner membrane of lipid bilayer; small layer of peptidoglycan that provides integrity and leads to forming a specific shape (without this the bacteria would pop open); another lipid bilayer with outer membrane containing LPS (also called endotoxin), which is a toxic compound that body responds to; space between outer and inner membrane is called the periplasm (not in gram positive)

Question 3

Gram Positive Components

Answer 3

Gram positive: large peptidoglycan layer (stains with Gram stain); inner membrane is lipid bilayer like gram negative; no outer membrane or LPS; no periplasm either; techoic acid (only in gram positive) and are pro-inflammatory (but not as powerful as LPS)

Question 4

LPS

Answer 4

Three structural components:

1. Lipid A
2. Core polysaccharide
3. O antigen

Lipid A is responsible for the endotoxin activity of LPS; well confined because inside the bacteria, but when destroyed the lipid A is released and causes the delayed fever response
Core is conserved within a species
O antigens: vary between different bacterial species

Question 5

Gram Stain

Answer 5

Heat the slide (fixation) then add crystal violet to stain (both stain initially), then iodine treatment to keep the stain, then decolorization process that washes away the crystal violet in gram negative but mostly stays for gram positive, then counterstain for gram negative bacteria (safranin)
Outcome: positives become purple and negatives stain red/pink

Question 6

Site of Replication

Answer 6

Intracellular: chlamydia has to be in the cell because needs to use the ATP to replicate since doesn’t produce its own
Extracellular: E. coli

Facultative – can do intracellularly or extracellularly; utilize both environments, but doesn’t prefer one over the other
Obligate: must be intracellular or extracellular

Question 7

Intracellular vs. Extracellular Replication

Answer 7

Intracellular:
Benefits: evolutionary purposes; use host’s ATP and/or nutrients (at first), can hide from the immune system (protection)
Challenges: the host dies then it dies; special machinery to get into the eukaryotic cell; nutrients are depleted eventually; has trouble spreading to other cells once inside one cell

Extracellular:
Benefits: spread easier (coughing for example) host to host or more widely inside host; access to nutrients is increased
Challenges: immune function (fighting mechanisms that can kill it)

Question 8

Aerobes vs. Anaerobes: Examples

Answer 8

Aerobes: Require oxygen for survival
Strict/Obligate (Mycobacterium tuberculosis)
Microaerophilic (Helicobacter pylori)

Anaerobes: Do not require oxygen for survival
Strict/Obligate (Clostridium tetani)
Facultative (Most medically important bacteria)
Aerotolerant

Question 9

Aerobes vs. Anaerobes

Answer 9

Aerobes:
Strict obligate: must have O2 or will not grow at all
Microaerophilic: require O2 at lower level; inside the mucous environment thus have lower O2 levels

Anaerobes:
Strict obligate: killed in presence of O2
Facultative: can do both O2 or no O2; grow better with O2, but can grow without it
Aerotolerant: grow equally well in both environments

Question 10

Professional vs. Opportunistic Pathogen

Answer 10

Professional Pathogen (aka: Primary Pathogen)
Efficient entry multiplication and spread within a healthy host

Opportunistic Pathogen (aka: Secondary Pathogen)
Entry and or multiplication require a breach in immunity 
Local or systemic breach

Obligate human Pathogen (Bordetella pertussis)
Facultative human Pathogen (Vibrio cholerae)

Question 11

Skin vs. Gut Normal Flora

Answer 11

Skin: predominantly Gram-positive bacteria

Gut: predominantly Gram-negative bacteria. Some normal flora of the large intestine are strict anaerobes.