direct-microbial-identification-using-an-automated-microbial

Direct Microbial Identification using An Automated Microbial Identification System to Facilitate the EUCAST RAST Method Without Mass Spectrometry

Gram-negative (GN) sepsis is a medical emergency where management in resource-limited settings relies on conventional microbiological culture techniques ...

All India Institute of Medical Sciences, Bhopal

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.

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

In view of paucity of information on serotype distribution of Dengue virus (DENV) in Central India, we undertook a cross-sectional study to identify clinical and virological characteristics of DENV serotypes that circulated in this region during the 2016 outbreak. Suspected cases were screened by ELISA for NS1 antigen and anti-DENV IgM antibodies. Serologically confirmed cases were subjected to RT-PCR based detection and serotyping. The RT-PCR results were confirmed by nucleotide sequencing. Genome-wide association was undertaken with DENV sequences from ViPR database and the immune evasion potential of infecting serotypes was ascertained by computing antigenic variability in B cell and Cytotoxic T cell (CTL) epitopes of all DENV proteins. The immunological basis of more prolonged viremia in DENV2-infected patients was also addressed through sequencing of NS2a gene and comparing the CTL activity in NS2a sequences identified among patients with ≤5 days and >5 days of illness. Among 166 serologically confirmed Dengue patients, 75 were positive for DENV RNA. Serotyping revealed predominance of DENV-1 and DENV-2, followed by DENV-3. Co-infection with multiple serotypes was observed in 15.5% of cases. In ~40% cases, DENV RNA was detectable beyond 5 days, among whom majority were DENV-2 infected (p = .044). Highest prevalence of antigenic variability was observed in B cell and CTL epitopes of DENV-2. The potential association between prolonged viremia and higher ability for immune evasion in DENV-2 patients was further corroborated with the observation of poorer HLA-I binding affinity in CTL epitopes observed in NS2a sequences retrieved from patients with >5 days of illness, compared to those with ≤5 days. This is the first report from central India revealing circulation of all DENV serotypes and high prevalence of co-infection with multiple serotypes. We also observed prolonged viremia upon DENV-2 infection, which could be potentially associated with its superior immune evasion potential.

Co-circulation of dengue virus serotypes in Central India: Evidence of prolonged viremia in DENV-2.

 is a well-known pathogen in salmonid fishes. It was believed to be non-pathogenic to humans because of inability to grow at 37°C. Here we present a case of a woman in her 20s who was diagnosed with abdominal tuberculosis 6 months previously but had not been compliant with the treatment. She presented with occasional febrile episodes, whitish vaginal discharge, burning micturition, anal ulcer, whitish discharge from mouth and recent onset breathlessness. Patient tested serologically positive for HIV-1, and  was isolated from urine sample. Patient was treated with antituberculosis therapy, antiretroviral therapy and antimicrobials. She showed marked improvement over the next few weeks. This case highlights the importance of recognition of rare organisms, especially in immunocompromised patients. The identification and subsequent treatment of such pathogens have improved since the advent of automated identification systems.

Shashank Purwar

Department of Microbiology

All India Institute of Medical Sciences, Bhopal

Direct Microbial Identification using An Automated Microbial Identification System to Facilitate the EUCAST RAST Method Without Mass Spectrometry

Shashank Purwar

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Microbiology

All India Institute of Medical Sciences, Bhopal

Direct Microbial Identification using An Automated Microbial Identification System to Facilitate the EUCAST RAST Method Without Mass Spectrometry

Department of Microbiology