20: clostridia supplement - jonathan

Question 1

Compare the aerobic status, gram stain, shape, and spore formation of...
C. tetanus
C. botulism
C. difficile
C. perfringens

Answer 1

All anaerobic Gram + rods
C. tetanus has terminal spore (Dx)
The rest have subterminal spore

Question 2

What is the catalase status and oxidase status of...
C. tetanus
C. botulism
C. difficile
C. perfringens

Answer 2

All are catalase and oxidase negative

Question 3

What is the source of infection for...
C. tetanus
C. botulism
C. difficile
C. perfringens

Answer 3

C. tetanus: acquired from soil via puncture wounds
C. botulism: oral ingestion of toxin mostly. Note toxin is heat labile.
C. difficile: Antibiotic suppression of normal flora leading to bacterial overgrowth and toxin production. Often a consequence of antibiotic use.
C. perfringens: Wound contamination with bacterial flora found in soil and GI tract

Question 4

What are the toxins associated with… 
How is Dx completed...
C. tetanus
C. botulism
C. difficile
C. perfringens

Answer 4

C. tetanus: Tetanus toxin leading to SPASTIC paralysis. Clinical Dx
C. botulism: botulism toxin leading to FLACCID paralysis. Detect toxin for Dx. Usually clinical Dx.
C. difficile: Extoxins A and B leading to damaged colonic cells. Detect toxin for Dx
C. perfringens: multiple toxins and proteases for tissue destruction and invasion (lecithinase, collagenase, etc…). double zone of hemoylsis on BAP

Question 5

What is the disease associated with...
C. tetanus
C. botulism
C. difficile
C. perfringens

Answer 5

C. tetanus: Tetanus syndrome. Generalized FLEXOR muscle spasm. No fever. No sensory loss.
C. botulism: Botulism. Flaccid paralysis. Can involve cranial nerves. No sensory deficit. Usu clinical Dx.
C. difficile: Pseudomembranous colitis. Diarrhea with yello-white plaque on colonoscopy.
C. perfringens: Gas gangrene. Gas byproducts of anaerobic metabolism and tissue necrosis due to tissue swelling and blood vessel compression.

Question 6

What are the variants syndromes of… (note: not all have variants)
C. tetanus
C. botulism
C. difficile
C. perfringens

Answer 6

C. tetanus: no variants
C. botulism: Infant botulism. Wound botulism.
C. difficile: no variants
C. perfringens: food poisoning due to enterotoxin of C. perfringen

Question 7

What is Tx for...
C. tetanus
C. botulism
C. difficile
C. perfringens

Answer 7

C. tetanus: Vaccine. Human anti-tetanus IgG. Supportive therapy. Respiratory support.
C. botulism: botulism type-specific antitoxin and supportive therapy. Respiratory support.
C. difficile: Stop prior antibiotic. Tx with vancomycin, metronidazole, or fidaxomicin
C. perfringens: Surgical debridemnet and penicillin

Question 8

What is prevention for...
C. tetanus
C. botulism
C. difficile
C. perfringens

Answer 8

C. tetanus: immunization
C. botulism: heat canned food to 100 degrees C
C. difficile: judicious use of antibiotics and handwashing
C. perfringens: good wound care

Question 9

Why are anaerobes catalase negative?

Answer 9

O2 production in aerobic fermentation can become H2O2.
Catalase breaks down H2O2
Anaerobes do not need this function
Note: catalase is part of the membrane cytochromes.

Question 10

What is the protocol for sampling anaerobes?

Answer 10

Send samples to lab ASAP
Use a container with thioglycolate, an oxygen-reducing agent
Inject specimen into specialized anaerobic container or in a capped syringe with no air
Use a Gaspak jar: NaBH4 + NaHCO3 plus H2O produces H2O and CO2

Question 11

What is the lab Dx for Clostridia species?

Answer 11

Lactose Egg Yolk Milk Agar coupled with microscopy

See Slide 17

Question 12

With the Lactose Egg Yolk Agar test what Clostridia do what?

Answer 12

C. perferingens are lechithinase + on egg yolk and ferment lactose
C. botulism are Lipase + on egg yolk and protease + on milk
C. tetani have tennis racket spore
C difficile is what is left