Korean J Lab Med.  2010 Aug;30(4):394-399. 10.3343/kjlm.2010.30.4.394.

Usefulness of a Chromogenic Selective Agar for the Identification of Bacillus cereus Isolated from Blood Cultures

• Jeong ES
• Shin JH
• Shin MG
• Suh SP
• Ryang DW

• KMID: 1781646
• DOI: http://doi.org/10.3343/kjlm.2010.30.4.394

Abstract

BACKGROUND
The incidence of Bacillus cereus bacteremia is increasing, but the identification of Bacillus species remains difficult. Brilliance Bacillus cereus agar (BBC agar; Oxoid, UK) is a new CHROMagar medium that allows selective isolation and identification of B. cereus; however, its clinical usefulness is seldom studied. We evaluated the usefulness of BBC agar to identify B. cereus isolates recovered from blood cultures.
METHODS
We analyzed a total of 53 blood isolates that showed a Bacillus-like morphology on Gram staining. All isolates were identified by using both the API Coryne (bioMerieux, France) and API 50CH/B (bioMerieux) systems. They were subsequently subcultured on BBC agar, incubated for 24 hr, and then examined for characteristic blue-green colonies. The clinical characteristics of patients whose isolates were identified as B. cereus were assessed.
RESULTS
Of the 53 isolates, 18 were identified as B. cereus by API 50CH/B. With the API 50CH/B system used as gold standard, the sensitivity and specificity for the identification of B. cereus were 100% (18/18) and 100% (35/35), respectively, using BBC agar, and 67% (12/18) and 100% (35/35), respectively, using the API Coryne system. Of the 18 patients with B. cereus bacteremia, 15 showed infectious signs, and 3 had more than 2 blood cultures positive for B. cereus on separate days.
CONCLUSIONS
Our study shows, for the first time, that BBC agar, with its good agreement and ease of use, is a valuable alternative to the API 50CH/B system for the presumptive identification of B. cereus isolates from blood cultures.

Keyword

Bacillus cereus; Chromogenic agar; API 50CH/B system; Identification

MeSH Terms

Adolescent
Adult
Agar/chemistry
Aged
Bacillus cereus/*isolation & purification
Bacteremia/*diagnosis/microbiology
Child
Child, Preschool
Chromogenic Compounds/*chemistry
Culture Media
Female
Gram-Positive Bacterial Infections/*diagnosis/microbiology
Humans
Infant
Infant, Newborn
Male
Middle Aged
Reagent Kits, Diagnostic
Sensitivity and Specificity

Figure

• 

  Fig. 1. Macroscopic morphology of Bacillus cereus (A) grown at 35°C on CHROMagar medium for 24 hr. Note the characteristic blue-green color of B. cereus, in contrast to other Gram-positive bacilli (B).

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