Biology subjects

Nori, S. R. C.

Publications and source records attributed to Nori, S. R. C..

2 recordsLinked to original sources

bioRxiv2019

Evolutionary route of resistant genes in Staphylococcus aureus

Multi-drug resistant S. aureus is a leading concern worldwide. Coagulase-Negative Staphylococci (CoNS) are claimed to be the reservoir and source of important resistant elements in S. aureus. However, the origin and evolutionary route of resistant genes in S. aureus are still remaining unknown. Here, we performed a detailed phylogenomic analysis of 152 completely sequenced S. aureus strains in comparison with 7,529 non-S. aureus reference bacterial genomes. Our results reveals that S. aureus has a large open pan-genome where 97 (55%) of its known resistant related genes belonging to its accessory genome. Among these genes, 47 (27%) were located within the Staphylococcal Cassette Chromosome (SCCmec), a transposable element responsible for resistance against major classes of antibiotics including beta-lactams, macrolides and aminoglycosides. However, the physically linked mec-box genes (MecA-MecR-MecI) that are responsible for the maintenance of SCCmec elements is not unique to S. aureus, instead it is widely distributed within Staphylococcaceae family. The phyletic patterns of SCCmec encoded resistant genes in Staphylococcus species are significantly different from that of its core genes indicating frequent exchange of these genes between Staphylococcus species. Our in-depth analysis of SCCmec resistant gene phylogenies reveals that genes such as blaZ, ble, kmA and tetK that are responsible for beta-lactam, bleomycin, kanamycin and tetracycline resistance in S. aureus were laterally transferred from non-Staphylococcus sources. In addition, at least 11 non-SCCmec encoded resistant genes in S. aureus, mostly present in plasmid are laterally acquired from distantly related species. Our study evidently shows that gene transfers played a crucial role in shaping the evolution of antibiotic resistance in S. aureus.

evolutionary biology↗

bioRxiv2019

Insights into the bacterial profiles and resistome structures following severe 2018 flood in Kerala, South India

Extreme flooding is one of the major risk factors for human health, and it can significantly influence the microbial communities and enhance the mobility of infectious disease agents within its affected areas. The flood crisis in 2018 was one of the severe natural calamities recorded in the southern state of India (Kerala) that significantly affected its economy and ecological habitat. We utilized a combination of shotgun metagenomics and bioinformatics approaches for understanding microbiome disruption and the dissemination of pathogenic and antibiotic-resistant bacteria on flooded sites. Here we report, altered bacterial profiles at the flooded sites having 77 significantly different bacterial genera in comparison with non-flooded mangrove settings. The flooded regions were heavily contaminated with faecal contamination indicators such as Escherichia coli and Enterococcus faecalis and resistant strains of Pseudomonas aeruginosa, Salmonella Typhi/Typhimurium, Klebsiella pneumoniae, Vibrio cholerae and Staphylococcus aureus. The resistome of the flooded sites contains 103 resistant genes, of which 38% are encoded in plasmids, where most of them are associated with pathogens. The presence of 6 pathogenic bacteria and its susceptibility to multiple antibiotics including ampicillin, chloramphenicol, kanamycin and tetracycline hydrochloride were confirmed in flooded and post-flooded sites using traditional culture-based analysis followed by 16S rRNA sequencing. Our results reveal altered bacterial profile following a devastating flood event with elevated levels of both faecal contamination indicators and resistant strains of pathogenic bacteria. The circulation of raw sewage from waste treatment settings and urban area might facilitate the spreading of pathogenic bacteria and resistant genes.

microbiology↗