Beta-Lactam resistance of Escherichia coli and Klebsiella pneumoniae strains isolated from urinary tract infections

Escherichia coli and Klebsiella pneumoniae, which are members of Enterobacte-riceae, are common pathogens of nosocomial and community acquired infections. Extended Spectrum Beta-Lactamase (ESBL) production of these species causes failure in treatment of infections. Fifty-three strains of E. coli and 52 strains of K. pneumoniae, agents of urinary tract infections, were included in the study. The susceptibilities of these strains against a variety of beta-lactam antibiotics and ESBL production rates were investigated. The E. coli strains were found to be susceptible to imipenem and resistant to cephalotine. The resistance rate to aztreonam and third generation cephalosporins was 8% and to amoxicillin-clavulanic acid and ampicillin 55%. All K. pneumoniae strains were found susceptible to imipenem and resistant to cephalotine. Resistance to aztreonam and third generation cephalosporins was determined in 31% of the strains. Resistance rates to amoxicillin-clavulanic acid, cefuroxim and piperacillin were 69%, 37% and 65%, respectively. Three (6 %) of 53 E. coli and 18 (35 %) of 52 K. pneumoniae isolates were demonstrated to produce ESBL. Imipenem was found to be the most effective beta lactam antibiotic against ESBL-producing E. coli and K. pneumoniae strains. Cefotaxime was found to be the most potent broad spectrum cephalosporin against ESBL-producing E. coli isolates. For ESBL-producing K. pneumoniae isolates, the most effective cephalosporin was ceftazidime.