Green synthesized silver nanoparticles from Ocimum sanctum: A potent inhibitor of biofilm forming ability and efflux pumps in bacteria causing bovine mastitis.

Therapeutic management of mastitis faces significant challenges due to multidrug resistance. In the present study, multi-drug-resistant (MDR) Staphylococcus spp, Klebsiella pneumoniae, and Escherichia coli were isolated from bovine clinical mastitis cases and the phenotypic and genotypic multidrug resistance profiling was carried out. Silver nanoparticles (AgNPs) were biosynthesized using Ocimum sanctum leaf extracts and characterized via UV Vis absorption, Fourier Transform Infrared Spectroscopy, X-ray diffraction studies, Energy dispersive spectroscopy and Electron Microscopy. The determined minimum inhibitory concentration and minimum bactericidal concentration of the AgNPs against the recovered MDR isolates were 62.5 µg/ml and 125 µg/ml respectively. At a concentration of 50 µg/ml, the AgNPs demonstrated biofilm inhibitory activities of 80.35 % for MDR E. coli, 71.29 % for S. aureus and 60.18 % for MDR K. pneumoniae. Post-treatment observations revealed notable differences in biofilm formation across bacterial isolates. Furthermore, AgNP treatment led to significant downregulation of expression of the efflux pump genes acrB, acrE, acrF, and emrB in Gram-negative isolates and norB in Staphylococci isolates. This research underscores the potential for the development of an eco-friendly antimicrobial alternative in the form of green synthesized silver nanoparticles to combat drug resistance offering potential antibiofilm and efflux pump inhibitory activities.

Metagenomic analysis exploring taxonomic diversity of rumen microbial communities in Vechur and crossbred cattle of Kerala state, India.

Rumen, one of the most productive diverse microbial habitats plays a vital role in the breakdown of feed to produce energy for maintenance and milk production in cattle. Culture-based procedures could identify only 10% of microbial species present in the rumen. Kerala, one of the southern states of India, owns only one native cattle breed, the Vechur cattle, which is noted for its short stature, disease resistance and adaptability to hot humid climate. Lower population density and decreased milk production potential of Vechur cattle led to the development of crossbred cattle of Kerala, with higher milk yield. A study was conducted to assess the rumen microbial profile of low productive Vechur cattle and high productive crossbred cattle for a better understanding of the relationship between the host and microbial community. DNA isolated from rumen liquor of five cattle each from both genetic groups maintained on standard ration (forage, concentrate ratio of 50:50) was subjected to whole metagenome sequencing. Bioinformatics and statistical analysis revealed that bacteria followed by archaea and eukaryota dominated in the Vechur cattle as well as the crossbred cattle rumen. Bacterial community was dominated by Bacteroidetes and Firmicutes phyla in both genetic groups with a higher Firmicutes to Bacteroidetes ratio of 0.45 in Vechur cattle. Among archaea, Euryarchaeota was more abundant, which constitute methanogens, contributing 98% of total archaeal reads. Prevalent protozoal genus found in the Vechur cattle rumen was Entodinium and in crossbred cattle rumen was Entamoeba. In Vechur and crossbred cattle rumen, 1086 and 1262 microbial species were observed exclusively and 4731 species were shared between habitats. There was a significant difference in total microbial species abundance between the two genetic groups and Vechur cattle displayed significantly higher microbial diversity compared to crossbred. As per literature, this is presumably the first report of rumen metagenome profile of Vechur cattle, a unique short breed of India.