Deck 17: Erysipelothirix, Lactobacillus, and Similar Organisms

Question 1

A catalase-negative, non-spore-forming, gram-positive rod that is not acid-fast could possibly belong to which group of bacteria?

A)Corynebacterium
B)Bacillus
C)Actinomyces
D)Erysipelothrix

Answer 1

D
The genera described in this chapter are all catalase-negative, non-spore-forming, gram-positive rods; some may exhibit rudimentary branching.

Question 2

Large, squamous epithelial cells with numerous attached pleomorphic gram-variable or gram-negative coccobacilli and rods are typical elements of a wet mount and Gram stain of vaginal secretions from a patient who has

A)bacterial vaginosis caused by Gardnerella vaginalis.
B)large numbers of large gram-positive rods.
C)large numbers of polymorphonuclear leukocytes.
D)All of the above are correct.

Answer 2

A
Gardnerella are small, pleomorphic gram-variable or gram-negative coccobacilli and short rods. The wet mount and Gram stain of vaginal secretions are key tests for diagnosing bacterial vaginosis caused by G. vaginalis. A wet mount prepared in saline reveals the characteristic "clue cells," which are large, squamous epithelial cells with numerous attached small rods. A Gram-stained smear of the discharge shows the attached organisms to be gram-variable coccobacilli. Clue cells typically are present, and large numbers of gram-positive rods (i.e., lactobacilli) representing normal vaginal flora are absent or few in number.

Question 3

A catalase-negative, non-spore-forming, non-branching, gram-positive rod that produces hydrogen sulfide when inoculated into TSI agar is most likely

A)Corynebacterium
B)Bacillus
C)Actinomyces
D)Erysipelothrix

Answer 3

D
Erysipelothrix is the only catalase-negative, gram-positive non-spore-forming rod that produces hydrogen sulfide (H₂S) when inoculated into triple sugar iron (TSI) agar. Some Bacillus spp. also blacken the butt of TSI, but they are catalase-positive and produce spores.

Question 4

Large numbers of large gram-positive bacilli are typical elements of a wet mount and Gram stain of vaginal secretions from a patient who has

A)bacterial vaginosis caused by Gardnerella vaginalis.
B)no apparent vaginal infection.
C)bacterial vaginosis caused by Lactobacillus sp.
D)gonorrhea

Question 5

Erysipelothrix can be described as

A)catalase-negative
B)not acid-fast
C)not branching
D)non-spore-forming
E)All of the above are correct.

Question 6

The wet mount and Gram stain of vaginal secretions from a patient who has bacterial vaginosis caused by Gardnerella vaginalis will reveal

A)large, squamous epithelial cells with numerous attached pleomorphic gram-variable or gram-negative coccobacilli and rods.
B)large numbers of large gram-positive rods.
C)large numbers of polymorphonuclear leukocytes.
D)All of the above are correct.