Bacterial Pathogenesis I Flashcards Preview

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Flashcards in Bacterial Pathogenesis I Deck (11):

Single vs. Multiple Flagellum

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


Gram Negative Components

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)


Gram Positive Components

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)



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


Gram Stain

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


Site of Replication

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


Intracellular vs. Extracellular Replication

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

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)


Aerobes vs. Anaerobes: Examples

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)


Aerobes vs. Anaerobes

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

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


Professional vs. Opportunistic Pathogen

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)


Skin vs. Gut Normal Flora

Skin: predominantly Gram-positive bacteria

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