Antimicrobial resistance and ESBL genes inE. coliisolated in proximity to a sewage treatment plant

This study was aimed to determine the prevalence of antibiotic-resistantEscherichia coliin the Szreniawa river with detailed aims of: (i) assessment of differences in the number of microbiological indicators of water quality in a diurnal cycle in a vicinity of the sewage treatment plant (STP); (ii) determination of prevalence of antimicrobial resistantE. coliisolated from three sites located at varying locations toward the STP; (iii) evaluation of the presence of extended-spectrum beta lactamase (ESBL)-determining genes in waterborneE. coliisolated from three sites of Szreniawa and (iv) genetic similarity assessment among theE. colipopulations. Bacteriological contamination (coliforms,E. coli,E. faecalis) was assessed using membrane filtration. FiftyE. colistrains, the species of which was confirmed by MALDI-TOF analysis, were subjected to antimicrobial resistance tests using standard disk-diffusion method. Double disk synergy test was used to assess the ESBL production and PCR tests were conducted to detect the ESBL-conferring genes and evaluate the genetic diversity. A significant variation in the number of bacteriological indicators was observed both within and between the sampling sites, suggesting the effect of effluent from the STP, point discharge of household sewage and agricultural runoff on the water contamination. The resistance to amoxicillin/clavulanate (90%) and ampicillin (36%) was most prevalent. Multidrug resistance was observed in 40% of strains but no ESBL-producing strains were observed phenotypically. However, the presence of three ESBL-determining genes (TEM,OXAandCTX-M) was detected in 24, 10 and 8% of strains, respectively. A number of factors caused considerable pollution of the river and numerous multidrug resistantE. colistrains were isolated.