Biology subjects

Siva, A. B.

Publications and source records attributed to Siva, A. B..

4 recordsLinked to original sources

bioRxiv2024

Prevalence and diversity of Helicobacter species in captive wild carnivores, and their implications for conservation management of endangered species

Helicobacter species colonize the gastrointestinal tract of various hosts, and have always been of interest due to their potential zoonotic transmission and impact on health of humans and animals. Comprehensive studies involving wild animals from different locations are lacking, hindering our understanding of their natural host range, prevalence, and genetic diversity. Here we investigated the prevalence and genetic diversity of Helicobacter species in thirteen wild carnivore species across twenty-two zoos and rescue centers in India by targeting partial 16S rRNA gene. We used sequences obtained from positive samples for phylogenetic analysis, and further evaluated factors influencing Helicobacter prevalence with generalised linear mixed models. We analysed 985 faecal samples of which 286 (29%) tested positive for Helicobacter, spanning all the host species included in this study. Helicobacter prevalence is strongly related to host species and location, and varied from 7.3% in common leopard to 80% in Indian fox. Phylogenetic analysis identified 59 unique genotypes clustered into 11 groups of three major Helicobacter types: enterohepatic, gastric, and unsheathed. Diverse Helicobacter species associated with diseases in humans and domestic animals were observed, such as H. canis, H. bilis, along with several novel strains/ species which require formal classification. Overall, this study highlights the wide occurrence and high genetic diversity of Helicobacter species in captive wild carnivores in India. Our findings underscore the need for regular health assessments in captive facilities to monitor Helicobacter infections, which could impact the health and management of endangered species. Future research should explore Helicobacter presence in biotic and abiotic factors in zoo and free-ranging populations following One Health approaches.

microbiology↗

bioRxiv2023

Composition of nasopharyngeal microbiota in individuals with SARS-COV-2 infection across three COVID-19 waves in India

Multiple variants of the SARS-CoV-2 virus have been plaguing the world through successive waves of infection over the past three years. Studies by independent research groups across geographies have shown that the microbiome composition in COVID-19 patients (CP) differ from that of healthy individuals (CN). However, such observations were based on limited-sized sample-sets collected primarily from the early days of the pandemic. Here, we study the nasopharyngeal microbiota in COVID-19 patients, wherein the samples have been collected across the three COVID-19 waves witnessed in India, which were driven by different variants of concern. We also present the variations in microbiota of symptomatic vs asymptomatic COVID-19 patients. The nasopharyngeal swabs were collected from 589 subjects providing samples for diagnostics purposes at Centre for Cellular and Molecular Biology (CSIR-CCMB), Hyderabad, India. CP showed a marked shift in the microbial diversity and composition compared to CN, in a wave-dependent manner. Rickettsiaceae was the only family that was noted to be consistently depleted in CP samples across the waves. The genera Staphylococcus, Anhydrobacter, Thermus, and Aerococcus were observed to be highly abundant in the symptomatic CP patients when compared to the asymptomatic group. In general, we observed a decrease in the burden of opportunistic pathogens in the host microbiota during the later waves of infection. To our knowledge, this is the first longitudinal study which was designed to understand the relation between the evolving nature of the virus and the changes in the human nasopharyngeal microbiota. Such studies not only pave way for better understanding of the disease pathophysiology but also help gather preliminary evidence on whether interventions to the host microbiota can help in better protection or faster recovery.

microbiology↗

bioRxiv2020

An Inexpensive RT-PCR Endpoint Diagnostic Assay for SARS-CoV-2 Using Nested PCR: Direct Assessment of Detection Efficiency of RT-qPCR Tests and Suitability for Surveillance

With a view to extending testing capabilities for the ongoing SARS-CoV-2 pandemic we have developed a test that lowers cost and does not require real time quantitative reverse transcription polymerase chain reaction (RT-qPCR). We developed a reverse transcription nested PCR endpoint assay (RT-nPCR) and showed that RT-nPCR has comparable performance to the standard RT-qPCR test. In the course of comparing the results of both tests, we found that the standard RT-qPCR test can have low detection efficiency (less than 50%) in a real testing scenario which may be only partly explained by low viral representation in many samples. This finding points to the importance of directly monitoring detection efficiency in test environments. We also suggest measures that would improve detection efficiency.

molecular biology↗

bioRxiv2019

Impaired liver regeneration and lipid homeostasis in CCl4 treated WDR13 deficient mice

Background and AimWDR13 - a WD repeat protein, is abundant in pancreas, liver, ovary and testis. Absence of this protein in mice has been seen to be associated with pancreatic {beta}-cell proliferation, hyperinsulinemia and age dependent mild obesity. Previously, we have reported that the absence of WDR13 in diabetic Leprdb/db mice helps in amelioration of fatty liver phenotype along with diabetes and systemic inflammation. This intrigued us to study direct liver injury and hepatic regeneration in Wdr13-/0 mice using hepatotoxin CCl4.\n\nMethodsMice were injected with CCl4 twice a week for 8 consecutive weeks. Controls were injected with vehicle (olive oil) similarly. After the last injection, mice were given a 10-days of recovery period and then sacrificed for physiological and molecular analyses.\n\nResultsIn the present study we report slower hepatic regeneration in Wdr13-/0 mice as compared to their wild type littermates after CCl4 administration. Interestingly, during the regeneration phase, hepatic hypertriglyceridemia was observed in Wdr13-/0 mice. Further analyses revealed an upregulation of PPAR pathway in the liver of CCl4-administered Wdr13-/0 mice, causing de novo lipogenesis.\n\nConclusionsThe slower hepatic regeneration observed in CCl4 administered Wdr13-/0 mice, may be linked to liver hypertriglyceridemia because of activation of PPAR pathway.

pharmacology and toxicology↗