Detection of extended-spectrum beta-lactamase-production in nosocomial strains of klebsiella pneumoniae, isolated from critical care units

ABSTRACT

Plasmid-encoded resistance to extended-spectrum cephalosporins and aztreonam due to extendedspectrum beta-lactamases [ESBLs] production is becoming a widespread dilemma in medical practice. Nosocomial pneumonia, urinary tract and bloodstream infections by ESBL-producing K. pneumoniae are difficult to treat, leading to high morbidity and mortality especially among patients in intensive-care units. The high prevalence of resistance to extended-spectrum cephalosporins among K. pneumoniae strains in our hospital directed the attention for further ESBLs confirmatory assays and investigations. In this work, all K. pneumoniae clinical strains [n=125] isolated from patients in critical care units during the year 2005 were characterized by CLSI standard screening and confirmatory methods for ESBL production, as well as detection of ESBL blaTEM and blaSHV plasmid genes. Thirty-four strains [27%] were confirmed to produce ESBLs, by the confirmatory methods, and all of them showed either blaSHV and/or blaTEM plasmid sequences. Some strains showed discrepancy among different cephalosporins tested, either by screening or confirmatory methods. Plasmid gene amplification confirmed the acquisition of resistant genes. In conclusion, despite being time-consuming and costly, complete characterization of ESBL strains using phenotypic standard confirmatory tests, combined with genotypic methods, is necessary for accurate ESBLs detection. Applying such strategy could promote patient recovery, minimize complications, and decrease the total hospital stay and treatment expenses, especially for intensive care patients