Co-occurrence of ESBLs and silver resistance determinants among bacterial isolates inhabiting polluted stretch of river Yamuna, India

• Published in: International journal of environmental science and technology (Tehran) 2019-10, Vol.16 (10), p.5611-5622
• Main Authors: Siddiqui, M. T., Mondal, A. H., Sultan, I., Ali, A., Haq, Q. M. R.
• Format: Article
• Language: English
• Subjects: Aquatic Pollution; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Environmental Science and Engineering; Original Paper; Soil Science & Conservation; Waste Water Technology; Water Management; Water Pollution Control
• ISSN: 1735-1472; 1735-2630
• DOI: 10.1007/s13762-018-1939-9

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 bla CTX-M was the most prevalent type of ESBL (60.3%) followed by bla TEM (47.9%) and bla SHV (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 bla CTX-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 bla CTX-M gene strengthens the hypothesis of heavy metal exert selection pressure for the emergence of antibiotic resistance.