Abstract
The considerations were Listeria, Corynebactrium, Erysipelothrix and Arcanobacterium species. The isolate was catalase-negative, which rules out Corynebacteria and Listeria species. The Gram-positive card of the Vitek 2 system can identify Erysipelothrix species, which eliminated that genus. At this point, a reverse CAMP test was performed to determine if the microorganism might be Arcanobacterium hemolyticum (A. hemolyticum). Arcanobacterium hemolyticum typically inhibits the beta hemolysis of Staphylococcus aureus on blood agar, hence resulting in a positive reverse CAMP test. The patient's isolate neither inhibited nor enhanced the β-hemolysis of S. aureus and was not A. hemolyticum. Additional biochemical tests were performed. The mystery microorganism is a tiny, Gram positive rod that is strongly β-hemolytic, catalase negative, ferments xylose and demonstrates no reaction on the reverse CAMP test. What is your diagnosis? (To be continued…).
Highlights
A reverse CAMP test was performed to determine if the microorganism might be Arcanobacterium hemolyticum (A. hemolyticum)
Arcanobacterium hemolyticum typically inhibits the beta hemolysis of Staphylococcus aureus on blood agar, resulting in a positive reverse CAMP test
Arcanobacterium pyogenes is a well-known pathogen in animals, causing a number of pyogenic infections in cattle and swine
Summary
Case history: Received 1 April 2020 Received in revised form 4 April 2020 Accepted 4 April 2020. The Gram-positive card of the Vitek 2 system can identify Erysipelothrix species, which eliminated that genus. At this point, a reverse CAMP test was performed to determine if the microorganism might be Arcanobacterium hemolyticum (A. hemolyticum). Arcanobacterium hemolyticum typically inhibits the beta hemolysis of Staphylococcus aureus on blood agar, resulting in a positive reverse CAMP test. Arcanobacterium hemolyticum typically inhibits the beta hemolysis of Staphylococcus aureus on blood agar, resulting in a positive reverse CAMP test (Figure 1).
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