Anaerobic Infections II

Question 1

What are the characteristics of a strict anaerobe?

Answer 1

• Can’t use O2 (as e- acceptor)
• Unable to break down H2O2
• Accumulate toxic superoxides in presence of O2

Question 2

What are the characteristics of an anaerobic infection?

Answer 2

• Anaerobes displaced from normal flora (Oral, GI, Skin, GU)
• Often polymicrobial
• Foul-smelling pus
• Brain abscesses

Question 3

Characteristics of clostridia:

Answer 3

Anaerobic
Gm+
Spore forming
Rods

Question 4

Types of clostridia and associated diseases:

Answer 4

C. diff - pseudomembranous colitus
C. tetani - lockjaw
C. perfringens - gas gangrene
C. botulinum - food poisoning

Question 5

Most common cause of invasive clostridial infections?

Answer 5

C. perfringens

Question 6

What are the characteristics of a C. perfringens infection?

Answer 6

Highly metabolically active
Produces gas
Found in soil and GI tract
no PMNs

Question 7

What are C. perfringens virulence factors?

Answer 7

Lecithinase exotoxin-phosphlipid that kills cells and hemolyzes RBCs in vitro and in vivo. Leads to myonecrosis. Digests egg yolk in agar/stormy fermentation

Question 8

C. perfringens infection pathogenesis?

Answer 8

contaminated traumatic wound
low oxidation/reduction potential
Necrosis of tissue
spread is rapid

Question 9

What are two anaerobic, non-spore forming, gram +, rods?

Answer 9

Actinomyces and propionibacterium

Question 10

What’s unique about actinomyces microscopically?

Answer 10

Colonies have a molar appearance (sulfur granules)
Resemble grains of sand
Form chains

Question 11

What is lumpy jaw?

Answer 11

Actinomyces infection, poor hygiene after invasive dental procedure. Can form draining sinus tract to skin.

Question 12

What problems do propionibacterium cause?

Answer 12

Causes acne on skin and can cause infection of prosthetic devices

Question 13

What are the characteristics of Bacteroides spp?

Answer 13

Anaerobic
Gm -
non-spore forming
rods

Question 14

B. fragilis causes what kind of infections?

Answer 14

Can cause intraabdominal abscess formation

Liver abcesses

Question 15

What’s B. fragilis’ major virulence factor?

Answer 15

Polysaccharide capsule=anti-phagocytic
Can tolerate a bit of O2 w/o being killed
Makes Beta=lactamases

Question 16

How do you make a B. fragilis lab dx?

Answer 16

B-lactamase

Can grow in bile-esculin agar

Question 17

Anaerobic infections above the waist have what two characteristics?

Answer 17

Related to dentition (peridontal spaces)

Sensitive to most antibiotics

Question 18

Anaerobic infections below the waist usually come from where?

Answer 18

GI (perforation, contamination, peritonitis)
GU (women, PID)
Also more antibiotic resistant

Question 19

What anaerobes are female GU tracts colonized by?

Answer 19

bacteroides, prevotella, lactobacillus, peptostreptococci

Question 20

What’s the first step in treating most anaerobic infections?

Answer 20

Removal of devitalized tissue/pus
Expose to oxygen/good perfusion
(Abx secondary)

Question 21

What antibiotics work for anaerobes?

Answer 21

Penicillins
Cephalosporins
Carbapenems
Clindamycin
Metronidazole-deep acidic environment 
Quinolones
Vancomycin