Experiences in rapid diagnosis of Brucella bacteremia using the Bact/Alert 120 system.

rucella species are slow growing, small gram-negative non-motile coccobacilli.1 The organism is strictly aerobic, nonencapsulated, and catalase and oxidase positive; it does not ferment carbohydrates and has variable urease activity.1-4 Brucellosis is usually transmitted to humans by direct contact with infected animals or by ingestion of unpasteurized diary products. In addition, occupational exposure of abattoir workers, veterinarians, and laboratory technicians may result in transmission of the disease through contaminated aerosols.4 All the 6 members of the genus are, in fact, serovars of a single species of which 4, namely, Brucella abortus, B. suis, B. canis, and especially B. melitensis are able to cause human infections.4 Brucellosis some how is common in our area. In our laboratory, blood cultures from suspected cases performed with the Bact/Alert 120 system (Organon Teknica) yield a positive signal, generally within 3-5 days. A 5-10 ml blood sample was used for blood cultures media inculcation. Aerobic blood cultures media was used. Gram stain of the blood culture medium reveals either gram-negative coccobacilli or no definite organisms. These positive broths were then subcultured into Trypticase soy agar medium with 5% sheep blood, a chocolate agar plate, a MacConkey agar plate, and urea slant. Inoculated isolator tubes were processed in a type III biological safety cabinet following the manufacturer's recommendations. Presumptive identification of Brucella species was performed on the basis of a typical microscopic picture showing small gram-negative coccobacilli; positive oxidase, catalase and urease tests; and negative sugar fermentation. API 20NE bacterial identification system (bioMerieux) tests were carried out to rule out any possibility of misidentifying this bacterium as Moraxella phenylpyruvica.3 Confirmation was carried out by agglutination test with specific antiserum.5 Over the last 2 years, our laboratory received 55 blood cultures from suspected cases of brucellosis. Six blood cultures were positive for brucellosis by the previously described method. Comparative data were obtained from our serology department by carrying out the serial dilution antibody test on those 55 blood cultures. Confirmatory results were obtained. B In summary, our experiences in the microbiological diagnosis of brucellosis that, it can be carried out in 2-5 days using the Bact/Alert system, which indicates a more rapid detection of Brucella than has been shown in previous reports. In an area of endemic of brucellosis, a positive and early direct urease test for signal positive blood culture broths containing gram-negative coccobacilli or no visible organisms may provide a presumptive diagnosis of brucellosis.