Screening for ESBL producing bacterial isolates of agricultural soil and profiling for multidrug resistance

Objectives

construction of agricultural environmental soil antibiotic resistance profile of the culturable bacteria in Kalyani, India, followed by the screening of ESBL producers harboring bla_tem, bla_shv, and bla_ctx-M.

Methods

158 Multi-Drug Resistant (MDR) bacteria were isolated from 18 agricultural sampling points in Kalyani, West Bengal, India followed by their Antibiotic resistance profiling against 15 test antibiotics. They were then screened for the presence of three Extended Spectrum Beta-Lactamase (ESBL) genes, namely bla_tem, bla_ctx-M and bla_shv by Double Disk Diffusion test and Polymerase Chain Reaction. The positive candidates were further identified using Amplified Ribosomal DNA Restriction Analysis followed by 16S rDNA sequencing.

Results

lowest resistance was observed against Vancomycin (0%) whereas the highest against the β lactam Ampicillin (97.5%). Very high resistance was observed against the 3rd generation cephalosporin Cefotaxime (90%). 16/158 bacterial isolates were positive for one or more of the three ESBL genes under investigation. 11 out of those 16 isolates (68.75%) harbored at least 2 genes and the rest 31.25% either had the bla_shv or the bla_tem gene. Phylogenetic analysis of the prevalent ESBL carrying organisms in the region demonstrated that the genes are being horizontally transferred across different bacterial orders and classes.

Conclusion

Significant antimicrobial resistance noted against 12 out of 15 antibiotics tested. Stenotrophomonas, Myroides, Pseudomonas, Enterobacter, and Serratia are found as culturable MDR bacteria carrying ESBL genes among the isolates. It is the first report of environmental ESBL carriage by Myroides isolated from India.