L 72 Anaerobic Bacterial Infections Flashcards
Why is O2 deadly to anaerobic bacteria?
They lack enzymes to deal with oxidative stress such as:
Superoxide dismutase-radical O2 into normal O2
Catalase-hydrogen peroxide into water
Peroxidase-oxidation by hydrogen peroxide
How do anaerobic bacteria produce energy?
They are fermenters
This process produces acids that often produce smells
Can also use other molecules besides O2 at end of electron transport chain
What type of bacteria predominates in the human body?
Anaerobic bacteria predominate
We didn’t know they were there for long time because we didn’t know to culture for them
Why are we interested in anaerobes?
Many are assoc. with infection
Anaerobe epidemiology
All ages
Kids: URT, head, neck
Commonly in patients with chronic infections
Most in abscesses, wounds, OB/GYN infections
Predisposing conditions:
Compromised circulation, diabetes, trauma
Prefer acidic conditions-necrotic tissue is acidic-lactic acid fermentation
Endogenous: often leak from gingiva, gut
Exogenous: soil, water, food
Can anaerobes survive in air?
Yes, but they cannot replicate
Tolerance depends on species and genera
Anaerobes general features
Fermentation
No O2 detoxifying enzymes
Putrid odor
Majority infections-polymicrobial cause disease by synergism
Intra-abdominal abscesses: coliforms + anaerobes
-Coliforms=CHEEK (Citrobacter, Hafnia, Enterobacter, E. coli, Klebsiella) all g(-)
Most commonly isolated anaerobes
Bacteroides fragilis Pigmented prevotella Prevotella Fusobacterium g(+) Peptostreptococcus g(-)
What is the most common, non-spore forming opportunistic anaerobic pathogen?
Bacteroides fragilis
Bacteroides Fragilis characteristics
Gram (-) bacillus Non-spore forming Very common opportunistic pathogen Found in colon Bile resistant Hardy, easily cultured Beta-lactamase SOD, inducible catalase (exception to rule) LPS–less endo-toxicity than others PSA (polysaccharide A capsule) -Phase variation: 1) Essential to abscess formation (attachment to peritoneal mesothelium), 2) Inhibits complement-mediated killing
Bacteroides fragilis clinical manifestations
Abscess formation: capsule adheres to peritoneal mesothelium, area surrounded by fibrous-collagen capsule; PSA only capable of abscess formation
Deep pain and tenderness below diaphragm
Fever and findings of acute abdomen
Infection can spread
Prevotella characteristics
Normal microbiota of mouth
G (-) coccobacilli
Abscesses of mouth, pharynx, brain, lung, PID, tubo-ovarian abscesses
Encapsulated, LPS–strong endotoxin, produce IgA, IgG, IgM proteases
Fusobacterium characteristics
Normal microbiota of mouth G (+) cigar-like form or like a fuselage Lemierre's syndrome: occlusion of the jugular vein from abscess Encapsulated LPS–strong endotoxin
What makes Peptostreptococcus unique?
It is the only anaerobic gram (+) coccus seen in clinical infections
Peptostreptococcus characteristics
Normal microbiota of mouth, colon, female genital tract
Associated with brain abscesses when with viridans streptococci
