Resistance of Klebsiella pneumoniae strains producing and not producing ESBL (extended-spectrum beta-lactamase) type enzymes to selected non-beta-lactam antibiotics.

Background: Bacteria of the Klebsiella genus may cause numerous infections in human, which are often treated with beta-lactam antibiotics. The fundamental mechanism of Klebsiella resistance to penicillins or cephalosporins involves the production of enzymes--extended-spectrum beta-lactamases (ESBLs). Because of resistance of many Klebsiella spp. strains to beta-lactams, alternative antibiotic therapy can make use of aminoglycosides and quinolones.

Material/methods: The study analyzed the prevalence of ESBL -type enzymes among 256 Klebsiella pneumoniae strains isolated from various clinical materials collected from patients hospitalized between 1997 and 2000. ESBLs were detected by double-disk synergy test (DDST). The prevalence of strains resistant to selected aminoglycosides (gentamicin, amikacin, netilmicin) and quinolones (ciprofloxacin, norfloxacin, nalidixic acid) in the particular years was analyzed. Drug sensitivity was determined by disk-diffusion method according to the recommendations of the National Reference Center for Microbial Drug Sensitivity.

Results: During the analyzed time interval, a significant increase of the number of K. pneumoniae ESBL(+) strains was noted: in 1997 - 16.5% (14/85) and in 2000 - 40.4% (22/54) (p<0.001). Among the ESBL(+) strains, an increase of the number of strains resistant to the tested antibiotics, except for nalidixic acid, was demonstrated

Conclusions: A statistically significant increase of multidrug-resistant K. pneumoniae strains, including strains producing ESBLs, was demonstrated in the analyzed material.