Abstract
BACKGROUND: Extended-spectrum β-lactamase (ESBL) production is the major resistance mechanism to β-lactam antibiotics in Enterobacteriaceae. In addition, emergence of plasmid-mediated quinolone resistance (PMQR) in ESBL-producing isolates has become a global threat for treatment of these infections. OBJECTIVES: We investigated the association between ESBL production and quinolone resistance in urinary isolates of K. pneumoniae. PATIENTS AND METHODS: A total of 196 urinary isolates of K. pneumoniae were collected from Imam Hussein Hospital in Tehran during a four year period (2008-2012). Antibiotic susceptibility was determined by disc diffusion and ESBL production was screened using the phenotypic confirmatory test (PCT). RESULTS: All isolates were susceptible to imipenem. Resistance to piperacillin and cefotaxime were 66.3% and 50.5%, respectively. Resistance to ceftazidime, amoxiclave, aztreonam, ceftriaxone, cefepime, nitrofurantoin, gentamicin, ciprofloxacin, nalidixic acid, ofloxacin, norfloxacin, levofloxacin, amikacin and pipracilin/tazobactam were less than 50%. ESBL production was detected in 92 isolates (46.9%) of which, 61.9% were resistant to nalidixic acid and 65.2% to ciprofloxacin. Multidrug-resistance was observed in 96.7% of ESBL producers. CONCLUSIONS: Our results showed coexistence of ESBL and quinolone resistance in the majority of the uropathogenic K. pneumoniae test isolates suggesting that care should be taken for the choice of antibiotic therapy.