Anaerobic Bacteria

Question 1

Why are most anaerobic infections actually polymicrobial (mixed)?

Answer 1

Strict anaerobes cannot use O2 because they do not have catalase (except bacteriodes) or superoxide dismutase and are unable to break down H2O2 to prevent damage from superoxide

Question 2

What are the types of anaerobic infections?

Answer 2

Toxin mediated where the preformed toxin is ingested (Botulism)
Toxin formed in Vivo (C. Diff, C. Perfringes, C. Tetani)

Question 3

What changes in physiology lead to deep tissue anaerobe infections?

Answer 3

Deep infections with endogenous anaerobes most commonly occur due to decreased vascular support and perfusion. On all mucocutaenous surfaces anaerobes predominate. Low O2 tension, warmth, moisture and substrate allow for opportunistic infection.

Question 4

What source of anaerobes is most important to consider in the treatment of war wounds?

Answer 4

Exogenous sources like dirt, spores, or foreign bodies

Question 5

What are the most likely sites of anaerobic infection?

Answer 5

Oral cavity, skin, GI system, GU tract

Question 6

What does foul smelling pus in an infection indicate?

Answer 6

Anaerobic infection

Question 7

How do you treat “above the waist” anaerobic infections?

Answer 7

Penicillin G, they should be susceptible to most Abx

Question 8

What are the major species of Clostridia that cause human disease?

Answer 8

C. Difficile
C. Botulinum
C. Perfringens
C. Tetani

C. Perfringens is the most common cause of invasive clostridial infection
All are gram positive toxin forming rods

Question 9

What is the virulence factor in invasive clostridial infection?

Answer 9

Lecithinase: a phospholipid that kills cells and hemolyzes RBCs in vitro and in vivo leading to dead tissue without the presence of PMNs

Question 10

What organism should you think of when you hear “lumpy jaw” and sulfur granules?

Answer 10

Actinomyces: a gram positive, non spore forming rod.
Macrocolonies under microscope sometimes look like grains of sand. The abcess gives a granular feel and therefore a lumpy jaw.
Actinomyces is associate with poor oral hygeine or after invasive dental surgery.

Question 11

What bacteria causes Acne?

Answer 11

Proprionobacterium: an anaerobic gram positive rod that does not form spores.

Question 12

What do you know about Bacteriodes?

Answer 12

Facultative anaerobe
Gram negative rod
Causes mixed infection
Antiphagocytic due to it’s polysaccharide capsule
May cause liver abscesses
Produces beta-lactamases (don’t use penicillin)

Question 13

What do you know about Fusobacterium?

Answer 13

Anaerobic, non-spore forming, gram negative rod
Long and filamentous on microscopy
Plays a role in periodontal disease
Linked to colorectal cancer