Deck 17: Erysipelothrix Lactobacillus and Similar Organisms

Question 1

A 28-year-old woman suspected of having sepsis caused by Gardnerella vaginalis has multiple blood cultures drawn; however, all sets were negative.Which one of the following statements explains this discrepancy?

A) The lot of blood culture media is most likely defective.
B) The blood culture bottles should be incubated anaerobically to enhance the growth of the organism.
C) Gardnerella vaginalis is inhibited by sodium polyanethol sulfonate (SPS) in the blood culture.
D) No discrepancy is present. Gardnerella vaginalis remains localized and does not cause sepsis.

Answer 1

C
Gardnerella is inhibited by SPS, which currently is used as an anticoagulant in most commercial blood culture media.An SPS-free medium or a medium with SPS that is supplemented with gelatin should be used when G.vaginalis sepsis is suspected.

Question 2

To test the validity of TSI media, quality control should be performed using which two organisms?

A) Gardnerella and Lactobacillus
B) Erysipelothrix and Gardnerella
C) Propionibacterium and Lactobacillus
D) Actinomyces and Arcanobacterium

Answer 2

B
Only Erysipelothrix produces H₂S in TSI agar.All other organisms are negative; therefore the only positive and negative organisms used for quality control purposes are Erysipelothrix and Gardnerella.

Question 3

A catalase-negative, non-spore-forming, nonbranching, gram-positive rod that produces hydrogen sulfide when inoculated into triple sugar iron (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 TSI agar.Some Bacillus spp.also blackens the butt of TSI, but it is catalase-positive and produces spores.

Question 4

A farmer has a localized, painful skin infection.Cultures are set up, and alpha-hemolytic, catalase-negative, and gram-positive bacilli are isolated.Based on this information, which of the following biochemical results are expected-urease, H₂S production in TSI, and nitrate reduction?

A) Positive urease, positive TSI, and positive nitrate
B) Positive urease, negative TSI, and negative nitrate
C) Negative urease, positive TSI, and negative nitrate
D) Negative urease, negative TSI, and negative nitrate

Question 5

A gram-positive bacillus identified as Lactobacillus is isolated in large quantities from the urine of a 16-year-old female.Based on this information, the patient should receive which antibiotic?

A) Penicillin
B) Tetracycline
C) Vancomycin
D) No antibiotics should be administered.

Question 6

Which organism is nonhemolytic on 5% sheep blood agar but hemolytic on human blood?

A) Weissella confusa
B) Arcanobacterium haemolyticum
C) Lactobacillus spp.
D) Gardnerella vaginalis

Question 7

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

Question 8

Clue cells are associated with which gram-positive bacilli?

A) Gardnerella vaginalis
B) Lactobacillus
C) Erysipelothrix rhusiopathiae
D) Arcanobacterium haemolyticum

Question 9

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

A) squamous epithelial cells with numerous attached pleomorphic gram-variable or gram-negative coccobacilli and rods.
B) numbers of large gram-positive rods.
C) numbers of polymorphonuclear leukocytes.
D) pleomorphic gram-negative rods with many leukocytes.

Question 10

The reverse Christie, Atkins, Munch-Petersen (CAMP)test is positive for these curved gram-positive bacilli.Which beta-hemolytic organism is used in conjunction with this organism in the reverse CAMP test?

A) Streptococcus pyogenes
B) S. agalactiae
C) S. saprophyticus
D) S. aureus