Identification and antimicrobial resistance of Enterococcus spp. isolated from surface water

In the study species distributions and antimicrobial resistance profiles were determined among riverine Enterococcus spp. Susceptibility of the isolates was tested against: ampicillin, imipenem, teicoplanin, vancomycin, erythromycin, linezolid, fosfomycin, ciprofloxacin, levofloxacin, moxifloxacin, tetracycline, high levels of gentamicin and streptomycin. The enterococci were detected in all of the analyzed water samples, periodically exceeding the mandatory standards of the EU Bathing Water Directive. Isolates were predominantly E. faecium (68.6%) and E. faecalis (21.6%) strains. The remaining isolates belonged to E. casseliflavus/gallinarum (5.2%), E. hirae (3.9%), and E. durans (0.7%). Of enterococci strains, 27% were susceptible to all tested antimicrobial agents and as much as 9% were classified as multiple-antibiotic-resistant (MAR). Resistance to erythromycin was common in all investigated areas (55%), followed by resistance to ciprofloxacin (22%) and tetracycline (14%). The resistance phenotypes related to glycopeptides and high-level aminoglycosides were also observed. Relatively low frequency of ampicillin resistance was found among studied strains, in contrast to the frequent use of this antimicrobial agent in Poland. According to the obtained results the Enterococcus should be regarded as an important genus, according to its potential contribution to dissemination of antimicrobial resistance in the water environment.