Abstract
The aim of this study was to assess the antimicrobial resistance and the prevalence of genes determining the presence of extended-spectrum beta-lactamase (ESBL) enzymes in Escherichia coli isolated from two major rivers of the Podhale region in southern Poland. In total, 196 E. coli isolates were analyzed—98 from each river—Białka and Zakopianka, collected in 8 campaigns, over the period of two years. Antimicrobial resistance was assessed using disk diffusion method and PCR tests were conducted to detect the ESBL genes. In E. coli isolated from Białka, the resistance to amoxicillin/clavulanic acid was detected most frequently (54.08%) and ESBL was detected in 14.29% of strains. In strains isolated from Zakopianka, most frequent resistance was observed toward ticarcillin (51.02%), while ESBL was observed in 16.33% of isolates. In the total pool of isolates, the resistance to amoxicillin/clavulanic acid was most frequent (48.98% of isolates) and ESBL producers comprised 15.30% of E. coli isolates derived from both rivers. Multidrug resistance was observed less frequently in strains derived from Białka (4 isolates resistant to 10 and more antimicrobials) than from Zakopianka, where 10 isolates were resistant to 10 and more antibiotics. Out of the tested ESBL genes blaTEM was detected most frequently (45.4% of isolates), whereas blaCTX-M1 and blaCTX-M3 were recorded in one isolate.
Highlights
Increasing consumption of antimicrobial agents throughout Europe results in their discharge to surface waters through sewage treatment plants via human urine and feces (Łuczkiewicz et al 2010)
Since surface water often acts as a receiver of effluent from treatment plants and sewage directly discharged from households or can be contaminated by animal feces, it should be considered as one of the possible routes for transfer of fecal species that are either resistant to antibiotics or carry the resistance-conferring genes (Wolny-Koładka and Lenart-Boron 2016)
As in the case of Białka, this source of contamination contributed to the increased prevalence of E. coli downstream of the treatment plant and the entire Zakopane locality (i.e., 32,300 CFU/100 ml at the site Poronin bridge, Z4)
Summary
Increasing consumption of antimicrobial agents throughout Europe results in their discharge to surface waters through sewage treatment plants via human urine and feces (Łuczkiewicz et al 2010). The overuse of antimicrobial agents in medicine, agriculture and animal breeding causes the selection of resistance in pathogenic bacteria and in commensal and environmental strains (van den Bogaard and Stobberingh 2000) Such strains may serve as a source of resistance genes that can be transferred to pathogenic strains of the same species and to other bacterial species due to horizontal gene transfer (Zabłotni and Jaworski 2014). The probability of exposure to the resistant strains of bacteria increases, since an infection might occur through contact or ingestion of contaminated surface water, for instance during recreational activities (Blaak et al 2014) This may result in both risks related to difficult in treatment infections or exposure to harmless strains of e.g., commensal-resistant bacteria, resulting in asymptomatic carriage of such strains (Blaak et al 2015). Since surface water (most frequently rivers) often acts as a receiver of effluent from treatment plants and sewage directly discharged from households or can be contaminated by animal feces, it should be considered as one of the possible routes for transfer of fecal species that are either resistant to antibiotics or carry the resistance-conferring genes (Wolny-Koładka and Lenart-Boron 2016)
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