Evaluation of "rapid urease test performed on broth of blood culture bottles indicated positive by automated blood culture system" - as a tool for early diagnosis of brucellosis

Brucellosis is a major zoonotic disease, the incidence of which is usually underestimated. The early diagnosis of human brucellosis continues to challenge clinicians because of its non-specific clinical features, slow growth rate in the blood culture, and the complexity of its serodiagnosis. Although the growth rate is slow, culture detection of circulating Brucella organisms remains a diagnostic cornerstone. The unique property of Brucella is to give urease test positive within 4 hours. So, we aimed our study to judge applicability of standard urease test done directly from blood culture bottles indicated positive by BACTEC 9050 for early diagnosis of brucellosis. Materials & Methods: The blood cultures indicated positive by BACTEC 9050 & having suspicion of Brucella infection were subjected to urease test. All the bottles were also sub-cultured over solid media for isolation & identification of bacteria. Result & Discussion : Out of total 50 bottles, 10 were found urease test positive within 4 hours of incubation (mean time 48 min) & all of these 10 bottles also revealed growth of Brucella spp. on subsequent subculture. Remaining 40 bottles, which were negative for urease test, revealed growth of other bacteria or didn't reveal any growth. The overall mean time for diagnosis of Brucellosis by blood culture & subsequent urease test was 74 hours with 100 % Positive predictive value. Conclusion : The rapid urease reaction was found to be the best and cost effective option to identify the Brucella spp. It can give positive reaction from the direct inoculation of blood from the blood culture bottle within 4 hours after indication of blood culture positivity by automated blood culture system; & thus it significantly reduces the time for preliminary identification of Brucella infection. This might also help to increase the rate of diagnosis for the Brucella spp