Bacterial Pathogenesis I Flashcards
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)
LPS
Three structural components:
- Lipid A
- Core polysaccharide
- 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
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)
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)
Aerotolerant
Aerobes vs. Anaerobes
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
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.