Abundance and antibiogram of <i>Escherichia coli</i> along stages of water treatment in Tamburawa Water Treatment Plant, Kano Nigeria

Abstract

Increasing reports of antibiotic resistant bacteria (ARB) and antibiotic resistant genes (ARGs) being detected in drinking water is of public concern. . This study was aimed at detecting the changes in abundance of Escherichia coli harbouring selected plasmid-mediated ARGs in different stages of water treatment at Tamburawa Water Treatment Plant (TWTP) which has the capacity to deliver 1.50x 10⁸L of drinking water per day to the populous Nigerian city of Kano. Water samples from clarification, filtration, disinfection, and storage stages of the plant were subjected to physicochemical and microbiological analyses. Following quantification using membrane filtration technique, standard cultural and biochemical techniques were used for identification and confirmation of E. coli. Susceptibility of the strains to 11 antibiotics (Tetracycline, Ciprofloxacin, Ampicillin, Augmentin, Chloramphenicol, Gentamicin, Ceftazidime, Cefuroxime, Cefixime, Ofloxacin and Nitrofurantoin) was then determined using disk diffusion method according to CLSI breakpoints. Representative strains resistant to β-lactams were chosen from each water treatment stage and screened for the presence of four selected ARGs–bla_NDM, bla_IMP, bla_FOX and bla_CMY–using polymerase chain reaction. The results showed no significant variations (p <0.05) in physicochemical parameters across the water treatment stages. Furthermore, E. coli, which was detected in all the treatment stages, had a high relative abundance of 0.241(24.1%).The isolated E. coli were 100% susceptible to Chloramphenicol and 87.5% susceptible to Ofloxacin and Gentamicin. Of the resistant strains, 33% were detected in storage stage, followed by filtration and clarification stage with 26% each and disinfection with the lowest (15%). It was also revealed that E. coli isolated from disinfection stage were 100% resistant to 5 antibiotics (Ceftazidime, Cefuroxime, Augmentin, Cefixime and Nitrofurantoin). ARGs amplified from plasmid DNAs were harboured by 90% of the E. coli isolated. This study therefore, concludes that resistant E. coli carrying different ARGs persist in drinking water produced in TWTP. These resistant isolates are most abundant at storage stage, and hence, the need for more efficient storage system.