Objective: To determine the relationship between the production of extended-spectrum beta-lactamases (ESBLs) in Klebsiella pneumoniae (K. pneumoniae) strains resistant to third-generation cephalosporins and resistance of these strains to antibiotics used.
Material and methods: A total of 157 cultures of K. pneumoniae resistant to third-generation cephalosporins were obtained from bronchial secretions of patients treated in intensive care units (ICUs) at Kaunas University of Medicine Hospital (KUMH). The secretions were cultured, and antibacterial susceptibility was tested in the Laboratory of Microbiology at KUMH according to the recommendations of the National Committee for Clinical Laboratory Standards (NCCLS). Using a method of double-disc synergy test, K. pneumoniae strains possibly producing ESBL were considered for further testing by means of E-tests. The resistance to carbapenems, piperacillin, gentamycin, amikacin, and ciprofloxacin was compared between ESBL-producing and non-ESBL-producing K. pneumoniae strains resistant to third-generation antibiotics.
Results: Almost one-third of K. pneumoniae strains (n=28, 32.8%) were resistant to third-generation cephalosporins in 2001 and 50.0% (n=36)--in 2004 (p<0.05). Half of the strains (n=7, 50%) were producing ESBLs in 2001 and 50% (n=12)--in 2004. All strains of K. pneumoniae were susceptible to carbapenems. Resistance rates to piperacillin and gentamicin were higher in ESBL-producing strains compared with non-ESBL-producing strains (94.7% (n=18) vs. 15.8% (n=3) (p<0.05) for gentamicin and 100% (n=19) vs. 36.8% (n=7) (p<0.001) for piperacillin, respectively). No significant differences were found in the resistance rates to amikacin and ciprofloxacin.
Conclusions: The resistance of K. pneumoniae strains, isolated from bronchial secretions of patients treated in ICUs at KUMH, to third-generation cephalosporins increased significantly during the period of 2001-2004. However, the proportion of ESBL-producing strains remained unchanged. Resistance to certain antibacterials could be suspected if ESBL production is present - higher rates of resistance to piperacillin and gentamicin were found in the group of ESBL-producing K. pneumoniae strains.