Anaerobes

Question 1

List 3 different mechanisms that may be responsible for a bacteria to be anaerobic

Answer 1

1) No cytochrome systems for the metabolism of O2
2) Little/no superoxide dismutase
3) Little/no catalase

Question 2

List some important anaerobic gram positive cocci and bacilli

Answer 2

(+) cocci: peptostreptococcus
(+) bacilli: clostridium spp.: perfringins, difficile, botulinum, tetani. propionibacterium spp.
(-) cocci: veillonella spp.,
(-) bacilli: bacteroides, fusobacterium

Question 3

Describe 5 clinical features of anaerobic infections

Answer 3

1) Source of infecting organism is usually the host
2) Alterations of host tissue provide suitable conditions for the development of opportunistic anaerobic infections
3) Typically polymicrobial involving up to 5 species
4) Abscess formation
5) Exotoxin involvement

Question 4

Describe 4 indications of anaerobic growth in culture

Answer 4

• foul odor
• failure to find growth aerobically
• pigmented or fluorescent colonies
• double zone of haemolysis

Question 5

Is antimicrobial susceptibility testing usually done on anaerobes? What are the drugs of choice for treating an anaerobic infection?

Answer 5

Not usually performed because anaerobes have a reasonably predictable antimicrobial susceptibility. You should test for beta-lactamase production though. The drugs of choice are: metronidazole, amox-clav, pip-taxo

Question 6

How are anaerobic infections usually treated?

Answer 6

Surgical intervention: draining abscesses, removing necrotic tissue, eliminating obstructions