Pattern of antibiotic susceptibility and detection of CTX-M-type extended spectrum beta-lactamases (ESBLs) in urinary isolates of Klebsiella pneumoniae in Mashhad

Extended spectrum beta-lactamases (ESBLs) are defined as enzymes capable of hydrolyzing oxyimino-cephalosporins. Selective pressure of overuse of new antibiotics may be associated with emergence of new types of beta-lactamases. The aim of this study was to identify urinary isolates of CTX-M ESBL-producing Klebsiella pneumoniae and to detect their pattern of antibiotic susceptibility Bacteria were isolated and identified from the urine samples sent to laboratories of two hospitals in Mashhad in 2010. Isolates were then tested for antimicrobial susceptibility by disc diffusion and examined for beta-lactamase production by double disk approximation test and CLSI (Clinical and Laboratory Standards Institute) confirmatory test. The blaCTX-M genes were detected by polymerase chain reaction using specific primer. Out of 100 studied urinary specimens, 19 bacteria were K. pneumonia, of which 47.4% were ESBL producer and all were positive for blaCTX-M gene. A large percentage of ESBL-producing isolates compared to ESBL-non producers were resistant to co-trimoxazole, gentamicin, and nalidixic acid and the difference for gentamicin was significant. Due to relatively high prevalence of ESBL-producing bacteria in the studied population, screening of infections caused by these bacteria would be important for appropriate treatment.