Gram- Anaerobic Rods

Question 1

in what part of the body would you find Gram(-) anaerobic rods among the flora?

Answer 1

large intestine (dominates here), dental plaque, some in small intestine/vagina/distal urethra

types of infections reflect normal their normal distribution

Question 2

what types of infections do the following Gram(-) anaerobic rods typically produce?
a. Bacteroides fragilis
b. Porphyromonas
c. Prevotella

Answer 2

a. Bacteroides fragilis - predominately intestinal, produce abdominal infections

b. Porphyromonas, (c.) Prevotella - predominately oral; produce infections of head, neck, respiratory tract, and bite wounds

Question 3

Where would you find Fusobacterium and Veillonella, both Gram(-) anaerobic, in the body?

Answer 3

oral flora

Fusobacterium: slender rods with tapered end
Veillonella: cocci

Question 4

what genus of bacteria does this describe?
- predominately found in oral flora, where it is abundant
- produces infections of head, neck, respiratory tract, and bite wounds
- makes black pigment
- colonies fluoresce red under UV light
- anaerobic

Answer 4

Porphyromonas: Gram(-) anaerobic rod

[remember that Gram(-) rods are very abundant in dental plaque, and infections often spread from endogenous sources]

Question 5

how do facultative bacteria help facilitate growth of anaerobic bacteria when grown together?

Answer 5

facultative bacteria use up ambient oxygen, which is beneficial for the anaerobic bacteria

infections with anaerobes usually contain multiply species of both anaerobic and facultative bacteria (and often spread from endogenous flora)

Question 6

what is the biological mechanism of the exotoxin produced by Bacteroides fragilis?

Answer 6

Bacteroides fragilis: Gram- anaerobic rod, intestinal flora

exotoxin (protease) cleaves E-cadherin, loosens epithelial zone adherens junctions between enterocytes —> outflow of fluid, diarrhea

Question 7

Which Gram(-) anaerobe lacks Lipid A in its LPS and has no endotoxic activity, but has an intensely inflammatory anti-phagocytic capsule which can provoke abscess formation?

Answer 7

Bacteroides fragilis: Gram- anaerobic rod, intestinal flora

Question 8

how is infection from Gram(-) anaerobic rods treated?

Answer 8

creation of oxygenated environment, surgical drainage of abscess + removal of necrotic tissue
(“to heal, use steel”)

Rx: clindamycin, metronidazole, penicillins (usually require several drugs for infection because many types of bacteria are present)

[note that aminoglycosides are NOT effective]