Abstract
Antibiotic resistance is one of the major current global health crises. Because of increasing contamination with antimicrobials, pesticides, and heavy metals, the aquatic environment has become a hotspot for emergence, maintenance, and dissemination of antibiotic and heavy metal resistance genes among bacteria. The aim of the present study was to determine the co-resistance to quinolones, ampicillin, and heavy metals among the bacterial isolates harboring extended-spectrum β-lactamases (ESBLs) genes. Among 73 bacterial strains isolated from a highly polluted stretch of the Yamuna River in Delhi, those carrying blaCTX-M, blaTEM, or blaSHV genes were analyzed to detect the genetic determinants of resistance to quinolones, ampicillin, mercury, and arsenic. The plasmid-mediated quinolone resistance (PMQR) gene qnrS was found in 22 isolates; however, the qnrA, B, C, and qnrD genes could not be detected in any of the bacteria. Two variants of CMY, blaCMY-2 and blaCMY-42, were identified among eight and seven strains, respectively. Furthermore, merB, merP, merT, and arsC genes were detected in 40, 40, 44, and 24 bacterial strains, respectively. Co-transfer of different resistance genes was also investigated in a transconjugation experiment. Successful transconjugants had antibiotic and heavy metal resistance genes with similar tolerance toward antibiotics and heavy metals as did their donors. This study indicates that the aquatic environment is a major reservoir of bacteria harboring resistance genes to antibiotics and heavy metals and emphasizes the need to study the genetic basis of resistant microorganisms and their public health implications.
Highlights
Ever since their discovery, antibiotics have provided many benefits in fields ranging from healthcare to agriculture
“Resistant” are the organisms, which could resist the effect of prescribed dosage concentration of antibiotics, “intermediate” are those bacteria, which are on the course to be resistant to prescribed drug concentration, and “sensitive” are those, which could not resist the prescribed concentration of antibiotics
The multiple antibiotic resistance (MAR) index of different bacteria was found to be in the range of 0.941–0.058
Summary
Antibiotics have provided many benefits in fields ranging from healthcare to agriculture. The emergence of antibiotic resistance has significantly reduced their efficacy and usefulness in treating humans and animals. Emergence of antibiotic resistance among microorganisms is associated with many complex metabolic and genetic factors. Among them, extended spectrum β-lactamases (ESBLs), AmpC β-lactamases, and plasmid-mediated quinolone resistance (PMQR) genes are major factors in resistance to a variety of drugs [1,2,3]. ESBLs are one of the most important mechanisms providing resistance against large numbers of life-saving drugs.
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