[Occurrence of alert pathogens in hospital environment. Part I. ESBL-producing enterobacteriaceae strains].

Introduction: Gram-negative bacteria belonging to the family Enterobacteriaceae cause severe and difficult to treat nosocomial infections. Strains of different species that produce extended-spectrum beta-lactamases (ESBL) were classified as alert pathogens. The purpose of this study was to analyze the occurrence and determination of antimicrobial susceptibility patterns of 134 ESBL-producing Enterobacteriaceae strains.

Methods: 96 (72%) isolates of Klebsiella pneumoniae and 38 (28%) isolates of Escherichia coli, were cultured from patients of Specialistic Hospital in Krakow, in the period from 2008 to 2010. Bacterial identification and antimicrobial susceptibility testing were performed by automated system Vitek 2 Compact (bioMerieux, Poland). Condition for inclusion in the study was the production by the strains of beta-lactamases with extended substrate spectrum (ESBL), which was confirmed using the automated method (Vitek 2 Compact system) and the disc-diffusion assay (DDST). Taken into consideration the first isolate from the patient.

Results: Bacilli of the species K. pneumoniae ESBL(+) were mainly isolated from respiratory tract samples (46%), urine (27%) and blood (12%). The dominant divisions in terms of frequency of isolation of these pathogens were anesthesiology and intensive care (42%), neurology and brain strokes (16%) and internal medicine (11%). Drugs with the highest efficiency against K. pneumoniae ESBL(+), in our in vitro studies, were: imipenem (100%), meropenem (100%), amikacin (90%) and tetracycline (75%). E. coli ESBL(+) isolates derived from patients of Anesthesiology and Intensive Care Unit (32%), Internal Medicine Unit (16%) and Division of Hematology (13%). Among all tested strains majority were obtained from respiratory tract samples, urine, swabs from wounds and blood (respectively 24%, 24%, 21% and 18%). Isolates of E. coli ESBL(+) demonstrated the greatest susceptibility in case of amikacin (92%) and piperacillin with tazobactam (76%), which suggests the highest activity of that antimicrobials against infections caused by examined strains. None of the analyzed bacilli were resistant to carbapenems.

Conclusions: Our study highlights the importance of characteristics of distribution of ESBL-producing K. pneumoniae and E. coli strains among hospitalized patient. Good antibiotic policies based on antibiotic resistant patterns can decrease the risk of ESBL infection.