LAUSR

In this study, we investigated the prevalence of ESBLs producing bacteria from highly polluted stretch of river Yamuna and co-occurrence of ESBLs and silver resistance gene among tested isolates. Water samples were collected from ten different polluted sites from Delhi stretch of river Yamuna, India. Out of 399 non-duplicate isolates screened, 121 (~ 30%) were found to be ESBLs producers. ESBLs positive isolates showed high level of resistance for β-lactam and non-β-lactam antibiotics, viz. ampicillin, cephalosporins, ciprofloxacin and polymyxin-B. A significantly high level of resistance (26.4%) was observed for last resort antibiotic colistin. 69% of ESBLs positive isolates exhibited multidrug resistance phenotype and high MAR index of different sampling sites ranging from 0.21 to 0.68. Molecular characterization revealed that blaCTX-M was the most prevalent type of ESBL (60.3%) followed by blaTEM (47.9%) and blaSHV (15.7%). We further observed co-occurrence of silver resistance determinants silE, silP and silS in 49.3%, 53.4% and 36.9% isolates harboring blaCTX-M genes. Conjugation transfer assay confirmed the successful transfer of plasmid encoding ESBLs and silver resistance determinants together. To the best of our knowledge, this is first report of co-occurrence of CTX-M and silver resistance gene from aquatic environment. Moreover, this study reports occurrence of ESBL genes in Bacillus safensis and Brachymonas chironomi not reported earlier. Co-occurrence of sil and blaCTX-M gene strengthens the hypothesis of heavy metal exert selection pressure for the emergence of antibiotic resistance.