Isolation, Identification and Antimicrobial Susceptibility of Brucella Isolates From Human Cases

Abstract

Introduction: Brucellosis is a worldwide zoonotic disease that remains an important public health problem in India. As clinical manifestations of human brucellosis are variable in nature, and no constellation of clinical findings can be considered, characteristic laboratory help is must in the diagnosis. In the laboratory, brucellosis is generally diagnosed by serological tests. Though many serological tests with different principles are available, serological testing does not provide direct evidence for the presence of the pathogen, hence isolation of Brucella spp. from the clinical specimen is considered to be the gold standard. Brucella is highly infectious and requires level 3 bio-containment facilities and technically skilled personnel, Brucella cultures are rarely performed. Due to the rampant use of rifampin for the treatment of tuberculosis and reports on development of resistance in virtually all organisms the sensitivity of Brucellae to the traditional drugs cannot be presumed. Aim: To isolate, identify the Brucellae from blood culture and to assess the antimicrobial susceptibility of the isolates to WHO recommended anti-brucellar antibiotics by agar dilution method. Materials and Methods: A total of 169 blood samples were collected for brucella culture, from 593 epidemiologically, clinically and serologically suspected cases of human brucellosis. Of the 169 blood cultures 77 yielded Brucella, of which nine were from the western Maharashtra and 68 from Northern Karnataka. The isolates were identified using conventional methods. The minimal inhibitory concentration (MIC) values for streptomycin, gentamicin, doxycycline, rifampin and trimethoprim-sulfamethoxazole were determined by using agar dilution method. Results: Isolation rate for Brucella was 45.5%. Of the 77 isolates, 75 were identified as B. melitensis and two as B. abortus. All the isolates were sensitive to all the drugs tested. Conclusion: Human brucellosis due to B.melitensis is fairly a common disease in this area. The current WHO recommended drug regimen for the treatment of human brucellosis continues to be effective as no drug resistance is noted in the study

Keywords

• agar dilution method
• antibiotic sensitivity
• blood culture