Genotypic characterisation of Mycobacterium tuberculosis isolates from tuberculous meningitis patients at a tertiary neurocare centre in Southern India.

AIMS: Specific genotypes of Mycobacterium tuberculosis (MTB) have been reported to cause outbreaks of pulmonary tuberculosis (TB) in geographical areas that are endemic to TB. However, since there is little epidemiological evidence on the association of particular genotypes that cause tuberculous meningitis (TBM), we sought to investigate the association of specific MTB strains with infection of the central nervous system (CNS). MATERIALS AND METHODS: We carried out a genetic characterisation of 89 MTB isolates from TBM patients at a Southern Indian tertiary neurocare centre and compared the genotypes with strains of pulmonary TB isolated from Indian immigrants in New York City. We applied the standard methods of genotyping of MTB, namely, IS6110-based restriction fragment length polymorphism and spoligotyping for strain identification, along with principal genetic grouping and single-nucleotide polymorphism cluster analysis. RESULTS: The analysis revealed a high-level of diversity amongst the strain population. The genotypes of the isolates from TBM patients paralleled the pulmonary TB strain population recovered from the Indian immigrants in NYC. CONCLUSIONS: We conclude that there is no apparent association between genotypes of MTB and propensity to infect CNS tissue.

Cryptococcus gattii serotype-C strains isolated in Bangalore, Karnataka, India.

During a retrospective study on cryptococcosis carried out in Bangalore, Karnataka, India, four Cryptococcus gattii strains were isolated from one HIV-positive and three HIV-negative patients, two of which had unknown predisposing conditions. Serotyping and genotyping showed that the isolates were C. gattii serotype C, mating-type α and genotype VGIV. All the isolates were identical by multilocus sequence typing, but presented a low similarity compared with a set of 17 C. gattii global control strains. The comparison with a larger number of previously reported C. gattii strains, including African isolates, revealed a close relationship between Indian and African serotype-C isolates.

Rapid diagnosis of acute bacterial meningitis: role of a broad range 16S rRNA polymerase chain reaction.

BACKGROUND: Acute bacterial meningitis is a significant cause of morbidity and mortality throughout the world. It can be difficult to diagnose, as the symptoms and signs are often non-specific. STUDY OBJECTIVE: To evaluate the performance of an in-house semi-nested polymerase chain reaction (PCR) assay targeting the 16S rRNA gene of Eubacteria for the rapid diagnosis of acute bacterial meningitis using cerebrospinal fluid (CSF) specimens. METHODS: A total of 112 CSF samples from 112 patients were used in the study. Among these, 32 samples were obtained from confirmed cases of Streptococcus pneumoniae, six samples were obtained from confirmed cases of Haemophilus influenzae, one sample from a confirmed case of Neisseria meningitidis, and 10 cases of clinically suspected acute bacterial meningitis. The remaining 63 CSF samples were obtained from patients with non-infectious illnesses (n = 47) of the central nervous system (CNS) and autopsy-confirmed tuberculous meningitis (n = 16). RESULTS: The assay had an overall sensitivity of 93% (95% confidence interval [CI] 0.81-0.98, negative predictive value = 95%) and a specificity of 98% (95% CI 0.92-1.0, positive predictive value = 98%). CONCLUSION: These preliminary findings suggest that the semi-nested PCR assay targeting the 16S rRNA gene may be used as a rapid test for the diagnosis of acute bacterial meningitis.

Cerebral phaeohyphomycosis caused by Scytalidium dimidiatum: a case report from India.

We report a case of cerebral phaeohyphomycosis caused by Scytalidium dimidiatum (synanamorph Nattrassia mangiferae) in a young, apparently immunocompetent Indian male. Etiological diagnosis was made by recovery of the fungus in culture and histopathological examination. The infection proved fatal despite aggressive antifungal therapy.

Rapid diagnosis of tuberculous meningitis: a comparative evaluation of in-house PCR assays involving three mycobacterial DNA sequences, IS6110, MPB-64 and 65 kDa antigen.

A PCR was standardized for amplifying three different mycobacterial--IS6110, MPB-64, 65 kDa DNA sequences. A comparative evaluation of the three PCR assays was carried out for the rapid diagnosis of tuberculous meningitis (TBM) using cerebrospinal fluid (CSF) specimens. While the IS6110 PCR was a single-step amplification reaction, the MPB-64 and 65 kDa antigen PCR assays were nested reactions. A total of 176 cerebrospinal fluid (CSF) samples from 176 patients were subjected to amplification of the three different mycobacterial sequences. Amongst them, 45 samples were obtained from confirmed cases of TBM (culture positive) and 56 samples were obtained from clinically suspected cases of TBM which were culture-negative. The remaining 75 CSF samples were categorized under the non-infectious and infectious illness of the central nervous system (CNS). Against a gold standard of culture, a sensitivity of 98% (NPV=99%) and a specificity of 100% (PPV=100%) was observed with the IS6110 PCR. Among the nested PCRs, a sensitivity of 91% (NPV=94%) and a specificity of 91% (PPV=85%) was observed with the MPB-64 assay, while the 65 kDa protocol had an associated sensitivity of 51% (NPV=76%) and a specificity of 92% (PPV=79%). These findings suggest that among the nested PCR assays, the MPB-64 PCR assay was associated with an enhanced degree of sensitivity and was comparable in terms of specificity. Our study also demonstrates that the IS6110 assay, while being a single-step PCR had the advantage of being a rapid test for the diagnosis of TBM, with increased sensitivity and enhanced specificity as compared to the nested PCR protocols.

Detection of antibody to Mycobacterium tuberculosis protein antigens in the cerebrospinal fluid of patients with tuberculous meningitis.

Antibodies against Mycobacterium tuberculosis antigens were detected by enzyme-linked immunosorbent assay in cerebrospinal fluid (CSF) samples obtained from 442 patients with tuberculous meningitis (TBM) and 102 control patients. Antibodies were found in the CSF of 87% of patients with clinical (culture-negative) TBM, 72% of patients with culture-positive TBM, and 65% of patients with autopsy-proven TBM. That anti-M. tuberculosis antibodies were detected in the CSF of patients with clinically diagnosed cases more frequently than in patients with culture-positive cases suggests that the detection of antibodies in CSF tends to decrease as bacillary load increases. Of the patients with clinical TBM who were coinfected with human immunodeficiency virus (HIV), 70% exhibited anti-M. tuberculosis antibody in CSF, which suggests that antibody responses in this group were substantially weaker than those in HIV-negative patients with clinical TBM. Some groups showed a stronger response to certain antigens, which suggests that antigen recognition patterns may be specific for the stage of disease.