Increasing bacterial resistance to antibiotics is one of the most serious problems in current medicine. An important factor contributing to the growing prevalence of multiresistant bacteria is application of antibiotics. This study aimed at analyzing the development of resistance of Enterobacteriaceae to selected beta-lactam, fluoroquinolone and aminoglycoside antibiotics in the University Hospital Olomouc and assessing the effect of selection pressure of these antibiotics.

Background: Klebsiella pneumoniae belongs to important nosocomial pathogens causing mainly hospital-acquired infections. Beta-lactam antibiotics are frequently used in the treatment of infections caused by K. pneumoniae, but by their selection pressure the bacteria become resistant. Excessive use of third-generation cephalosporins is a risk factor for the occurrence and spread of ESBL-producing bacterial strains. The goal of this study was to describe the utilization of third-generation cephalosporins and to analyse their selection pressure on K. pneumoniae in the University Hospital in Olomouc. Methods: Data on the utilization of antibiotics in the hospital were obtained for the period 1997–2005 from the computerized database and expressed in defined daily doses per 100 bed-days (DBD). The data were processed according to the ATC/DDD system. Klebsiella pneumoniae strains were isolated from clinical material obtained from hospitalized patients. Results: Consumption of third-generation cephalosporins, which was 1·79 DBD in 1997, decreased to 0·93 in 1999, remained stable until 2002, and then increased to 2·40 DBD in 2005. During the 9-year period analysed, a total of 9564 strains of K. pneumoniae were isolated. The ESBL-positive K. pneumoniae strains frequency increased from 8% to 18%. Conclusions: Increasing utilization of third-generation cephalosporins was associated with a statistically and clinically significant increased incidence of ESBL-positive K. pneumoniae strains.