Características microbiológicas de Klebsiella pneumoniae isoladas no meio ambiente hospitalar de pacientes com infecção nosocomial.

Abstract

Klebsiella pneumoniae is an important ethiological agent of infections in the nosocomial environment and due to indiscriminate use of broad spectrum antimicrobials, especially of third generation cephalosporins; a selective pressure is produced, what favors the growth of strains producing extended spectrum β-lactamases (ESBLS). These enzymes hydrolyse broad spectrum cephalosporins and monobactams, but are inhibited by β-lactamases inhibitors. ESBLs have been identified in other pathogens but are more often found in Klebsiella pneumoniae and Escherichia coli. The fails in the detection of ESBL increase the mortality and morbity rates, favors the occurance of multirresistant drug outbreaks and increase the costs to control these microorganisms. The purpose of this study was to evaluate the prevalence, susceptibility to antimicrobial agents and genomic variability of ESBL Klebsiella pneumoniae in the hospital with the highest prevalence of ESBL producing isolates in Goiânia. A total of 61 strains of Klebsiella pneumoniae (89,9%) and 7 of Klebsiella oxytoca (10,1%) were isolated from January 2005 to May 2006 from hospitalized patients in three hospitals in Goiânia. All the isolates were identified and the susceptibility to antimicrobials tested by the authomatized semiquantitative method (MicroScan WalkAway® - Dade Behring, USA). The double-disk diffusion was used to detect the ESBL producing strains; a disk containing amoxicillin/clavulanate was placed as the inhibitor of β-lactamase 20mm from the oxymino-β-lactam. Enhancement of the zone inhibition of the oxymino β-lactam caused by the clavulanate disk was considered as evidence of ESBL production. The chomossomal DNA analysis was performed by Pulsed-field gel electrophoresis (PFGE). The prevalence of ESBL producing Klebsiella pneumoniae was high (25%, 28.5% and 66.7% respectively) and the antimicrobial resistance rates were higher among ESBL producing isolates. Only the imipenem showed excellent activity in vitro. The chomossomal DNA analysis showed a great variability among 5 strains (multiclonal) and similarity among 6 strains (clonal) producing ESBL.