Characterization of ESBL-producing Escherichia coli and Klebsiella pneumoniae strains isolated from urine of nonhospitalized patients in the Zagreb region

Aim To determine the prevalence of ESBL-producing Escherichia coli and Klebsiella pneumoniae strains isolated from uring of nonhospitalized patients during a three-year period, to determine their antibiotic susceptibility, investigage the transfer of ESBL genes with cotransfer of resistance and to characterize isolated beta-lactamases. Methods Antimicrobial suceptibility was determined by disk diffusion and broth microdilution methods. The double-disk test was used for ESBL detection. Transfer of resistance was performed by broth mating method and characterization of isolated beta-lactamases by polymerase chain reaction. Results The prevalence of ESBL-producing E.coli was 1.5% and K.pneumoniae showed high resistance rates to amonoglycosides. cotrimoxazole, nitrofurantoin and quinolones while ESBL-producing E.coli isolates, with exception of high aminoglycoside resistance, showed low resistance rates to other antibiotics. Successful conjugation of ESBL genes was obtained with 25% E.coli and 76.2% K.pneumoniae strains. Comparing to E.coli, K.pneumoniae strains showed higher rates of aminoglycoside and cotrimoxazole resistance cotransfer. Beta-lactamases of investigated strains belonged to TEM, SHV and CTX-M families. Conclusion The existence of multiple-resistant ESBL-producing E.coli and K.pneumoniae strains was confirmed in observed outpatient population. ESBL-producing K.pneumoniae isolates, in contrast to ESBL-producing E.coli, showed higher resistance rates to non-beta-lactam anitbiotics, probably caused by cotransfer of resistance genes located on the same plasmid as EsNL genes. It is important to monito the prevalence of such strains and their possible spreading in the outpatient population of the Zagreb region.