Anaerobic Bacteriology

Question 1

What is an obligate anaerobe?

Answer 1

0% O2, Strict

Bacteroides, Prevotella, Fusobacterium spp.

Question 2

What is a facultative anaerobe?

Answer 2

Can grow in atmospheric O2 or anaerobic environment

Question 3

What is aerotolerant?

Answer 3

Up to 5% O2, grows best in anaerobic but can grow in reduced or atmospheric O2

Question 4

What are endogenous anaerobes?

Answer 4

Anaerobic human normal flora, opportunistic

Question 5

What are exogenous anaerobes?

Answer 5

Not human normal flora, from soil and environment

Question 6

What is the best way to obtain an sample for anaerobic culture?

Answer 6

• Tissue biopsy

- Aspiration using needle or syringe

Question 7

What specimens are not recommended and why? (Collection techniques)

Answer 7

Swab specimens

• Prone to drying
• Easily contaminated
• Fibres can hold onto microorganisms

Question 8

If using a swab for collection, what is recommended?

Answer 8

• Oxygen-free transport medium

- “Flock swabs”

Question 9

What are the 3 kinds of anaerobic transport systems?

Answer 9

1. Rubber-stoppered vial for liquid specimens
2. Oxygen-free collection tube for swabs
3. Self-contained anaerobic bag for tissue specimens

Question 10

What 2 organisms have brick-red fluorescence under long-wave UV lieght?

Answer 10

• Prevotella spp.

- Porphyromonas spp.

Question 11

Which organisms have sulfur granules?

Answer 11

• Actinomyces spp.
• Propionibacterium spp.
• Eubacterium nodatum

Question 12

Methods for direct detection for C.diff toxin?

Answer 12

• Tissue culture for sytotoxin (Toxin B)
• Latex agg (A or B)
• ELISA (A or B)

Question 13

What can be done differently in a Gram stain for anaerobic Gram negatives?

Answer 13

• Safranin 3-5 minutes
• 0.5% basic fuchsin
• Diff [ ] reagents
• Gram enhancers after decolourization (suppresses background)

Question 14

List the anaerobic media that can be used.

Answer 14

• Anaerobic BA
• Bacteroides bile esculin (BBE)
• Laked kanamycin-vancomycin blood (LKV) agar
• Anaerobic PEA
• Egg yolk agar (EYA) (for C.diff)
• Cycloserine cefoxitin fructose agar (CCFA) (for C.diff)
• Schaedler’s broth
• Thioglycollate broth (enriches small #’s)

Question 15

Incubation requirements for anaerobes?

Answer 15

• 35-37 for 48hrs
• Early exposure to O2 can kill orgs.
• Re-inc up to 5 days
• Thio broth 7 days, use for subculture

Question 16

Describe method for jar incubation.

Answer 16

• Gas packs
• Palladium catalyst for O2 removal
• Methylene blue or resazurin indicators (change to white)

Jar should be:

• warm to touch (w/in minutes)
• Mist on inner walls
• Strip is white

Question 17

What are the antibiotics used for presumptive ID of anaerobes?

Answer 17

• Kanamycin
• Colistin
• Vancomycin

Question 18

List common tests for anaerobic ID.

Answer 18

• Catalase
• Spot indole
• Nitrate disc
• Bile disc (Gram neg)
• SPS disc (Gram pos cocci)
• Susceptibility Discs (k,v,c)
• Lecithinase production on egg yolk agar (EYA)
• Lipase production
• Urease
• Nagler reaction (Gram pos )
• Reverse CAMP (Gram pos)

Question 19

List methods for definitive ID of anaerobes.

Answer 19

• PRAS biochemicals
• Mini biochemicals (ex: api 20A)
• Correlate gram, colony morph and site of infection.

Question 20

Antimicrobial therapy for: Bacteroides fragilis group, other Bacteroides spp, Porphyromonas spp, Prevotella spp, Fusobacterium spp.

Answer 20

• Beta-lactams/ combos, imipenem, metronidazole, chloramphenicol
• Cefoxitin (cephalosporin)
• Moxifloxacin (fluoroquinolone)

Question 21

Antimicrobial therapy: Clostridium spp.

Answer 21

• Penicillins +/- beta-lactamase inhibitors, imipenem
• Metronidazole/vanco for C.diff

Botulism + C.perfringens: Non

Question 22

Antimicrobial therapy: Actinomyces spp, Propionibacterium spp.

Answer 22

• Penicilins +/- beta-lactamase inhibitor combos, imipenem, cefotaxime, ceftizoxime

Question 23

Antimicrobial therapy: Peptostreptococcus spp.

Answer 23

• Penicilins, most cephalosporins, imipenem, vanco, clindamycin, chloramphenicol