Utility of Serological Tests in the Era of Molecular Testing for Diagnosis of Human Brucellosis in Endemic Area with Limited Resources.

BACKGROUND: The culture has always been the gold standard test for diagnosis of human brucellosis but the conventional Brucella diagnostic tests viz. serology and culture are often beset with poor specificity & sensitivity respectively. The culture positivity rates for Brucella vary from 92% for bone marrow to 10% for non-blood samples and also dependent on the type of sample. The primary immune-determinant for Brucella species is the cell wall surface lipopolysaccharide, which is antigenically similar to other gram-negative rods. Hence, Brucella serological tests cross react with Escherichia coli 0116 and 0157, Salmonella urbana, Yersinia enterocolitica 0:9, Vibrio cholerae, Xanthomonas maltophilia and Afipia clevellandensis infections, which are common in developing countries also having higher incidence of brucellosis. AIM: The aim of the study was evaluation of conventional serological techniques and PCR for diagnosis of human brucellosis in and around north Karnataka which is endemic for brucellosis and patients often present with elevated base line antibody titers and confounding clinical manifestations. MATERIALS AND METHODS: Blood/serum samples of 400 patients suffering from acute undifferentiated fever (AUF) were subjected to culture, Brucella slide agglutination test (SAT), standard tube agglutination test (STAT coupled with 2 ME) and PCR. RESULTS: Of the 400 AUF patients, anti-Brucella antibodies were detected by SAT and STAT in serum of 35 and 34 patients respectively. IS711 gene for Brucella was identified in 32 patients by PCR. Twenty samples yielded Brucella in culture on biphasic medium with average incubation period of 9 days. All patients having titer of ≥ 160IU / ml in STAT were found positive by PCR also. CONCLUSION: Brucella STAT corroborated well with PCR results in all those cases where antibodies were present at least one dilution above cut-off value of 80 IU/ml. We probably need to raise cut-off titers to ≥160 IU/ml because of endemic region. The SAT was upheld as very good quick, easy to perform and economical screening test for human brucellosis. SAT as rapid screening test and STAT as more definitive test can be very well adopted by laboratories working in resource scarce settings for diagnosis of human brucellosis in absence of PCR even for population with normally elevated antibodies levels due to residing in Brucella endemic areas.

PCR confirmation of cutaneous manifestation due to Brucella melitensis.

Human brucellosis, a zoonotic disease, is endemic in the Belgaum district, Karnataka, India. A male patient presented with a generalized itchy rash. Blood was sent for venereal disease research laboratory testing. Screening was carried out for Brucella antibodies following hospital policy and diagnosis was confirmed by PCR.

Neurobrucellosis presenting as an intra-medullary spinal cord abscess.

BACKGROUND: Of the diverse presentation of neurobrucellosis, intra-medullary spinal cord abscess is extremely rare. Only four other cases have been reported so far. We present a case of spinal cord intra-medullary abscess due to Brucella melitensis. CASE PRESENTATION: A forty-year-old female presented with progressive weakness of both lower limb with urinary incontinence of 6 months duration. She was febrile. Neurological examination revealed flaccid areflexic paraplegia with T10 below sensory impairment including perianal region. An intramedullary mass was diagnosed on Magnetic Resonance Image (MRI) scan extending from T12 to L2. At surgery, a large abscess was encountered at the conus medullaris, from which Brucella melitensis was grown on culture. She was started on streptomycin and doxycycline for 1 month, followed by rifampicin and doxycycline for 1 month. At 2-year follow-up, she had recovered only partially and continued to have impaired bladder function. CONCLUSION: Neurobrucellosis, if not treated early, can result in severe neurological morbidity and sequelae, which may be irreversible. Hence it is important to consider the possibility of neurobrucellosis in endemic region and treat aggressively.