Distribution ofblaTEM,blaSHV,blaCTX-MGenes Among Clinical Isolates ofKlebsiella pneumoniaeat Labbafinejad Hospital, Tehran, Iran

Abstract

Extended-spectrum β-lactamase (ESBL)-producing isolates of Klebsiella pneumoniae have been increasingly recognized in the hospital settings in Iran as well as throughout the world. The aim of this study was to detect and determine the genes encoding the ESBLs including bla_TEM, bla_SHV, and bla_CTX-M groups among the K. pneumoniae isolates at Labbafinejad Hospital by polymerase chain reaction (PCR) and characterize them by direct sequencing of PCR products. Eighty-nine isolates were isolated from patients at different wards during March 2008–March 2009. They were identified as K. pneumoniae using biochemical tests. Susceptibility of isolates to 17 different antimicrobial agents was determined using agar disk diffusion method. The phenotypic confirmatory test was used to screen the isolates for production of ESBLs. To amplify the bla_SHV the template DNA was extracted by boiling method. Plasmid DNA was extracted using minipreparation kit and used as template in PCR for detection of bla_TEM and bla_CTX-M. The selected PCR products were sequenced and analyzed. All 89 strains were susceptible to imipenem. The rates of resistance to different antibiotics were in the following order: aztronam (79.7%), cefexime (67.4%), cefpodoxime (66.2%), cefotaxime (65.1%), ceftazidime (61.7%). The phenotypic confirmatory test detected 62 isolates (69.7%) as ESBL-producing K. pneumoniae. The prevalence of genes encoding ESBLs were as follows: bla_TEM 54% (n = 48), bla_SHV 67.4% (n = 60), bla_CTX-M-I 46.51% (n = 40), and bla_CTX-M-III 29% (n = 25). The bla_CTX-M-II and bla_CTX-M-IV were not detected. All bla_TEM types were characterized as bla_TEM-1 and all bla_CTX-M-I were identified as bla_CTX-M-15. The SHV types were characterized as SHV-5, SHV-11, and SHV-12. The rate of ESBL at Labbafinejad Hospital was 25% increase in a 4-year study that ended in March 2009. It appears that bla_TEM-1, bla_SHV-5, bla_SHV-11, bla_SHV-12, and bla_CTX-M-15 are the dominant ESBLs among the resistant strains of K. pneumoniae in Iran.