Antibiotic Resistance Characterization of Environmental E. coli Isolated from River Mula-Mutha, Pune District, India

In the current study, ceftazidime- and ciprofloxacin-resistant&mdash;or dual drug-resistant (DDR)&mdash;<i>E. coli</i> were isolated from river Mula-Mutha, which flows through rural Pune district and Pune city. The DDR <i>E. coli</i> were further examined for antibiotic resistance to six additional antibiotics. The study also included detection of genes responsible for ceftazidime and ciprofloxacin resistance and vectors for horizontal gene transfer. Twenty-eight percent of the identified DDR <i>E. coli</i> were resistant to more than six antibiotics, with 12% being resistant to all eight antibiotics tested. Quinolone resistance was determined through the detection of <i>qnrA</i>, <i>qnrB</i>, <i>qnrS</i> and <i>oqxA</i> genes, whereas cephalosporin resistance was confirmed through detection of TEM, CTX-M-15, CTX-M-27 and SHV genes. Out of 219 DDR <i>E. coli</i>, 8.2% were <i>qnrS</i> positive and 0.4% were <i>qnrB</i> positive. Percentage of isolates positive for the TEM, CTX-M-15 and CTX-M-27 genes were 32%, 46% and 0.9%, respectively. None of the DDR <i>E. coli</i> tested carried the <i>qnrA</i>, SHV and <i>oqxA</i> genes. Percentage of DDR <i>E. coli</i> carrying Class 1 and 2 integrons (mobile genetic elements) were 47% and 8%, respectively. The results showed that antibiotic resistance genes (ARGs) and integrons were present in the <i>E. coli</i> isolated from the river at points adjoining and downstream of Pune city.