Relationship between presence of genes encoding ESBLs and antimicrobial susceptibility pattern in Escherichia coli clinical isolates

Escherichia coli harboring extended spectrum β-lactamase (ESBLs) are significantly resistant to other antibiotics and caused several health problems. The present study was carried out to characterize the ESBL types and to determine their pattern of resistance to four antimicrobial agents in clinical isolates of E. coli.
Material and During April 2012 to May 2013, 500 clinical isolates of E. coli were collected from two hospitals in Boroujerd. Phenotypic screening and confirmation tests for ESBL detection and antibiotic susceptibility testing were performed according to Clinical and Laboratory Standards Institute (CLSI) guidelines. Minimum inhibitory concentration of imipenem, meropenem, amikacin and ceftriaxone was determined by the E-test method. All ESBLs producing isolates were examined for presence of the TEM, SHV and CTX-M genes by PCR method.
All of the studied isolates were susceptible to imipenem and meropenem. Additionally, among ESBLs producer isolates good susceptibility to amikacin and ceftriaxone (P-value 0.5) was observed. The prevalence of the TEM, SHV and CTX-M genes among 190 ESBLs producing isolates was as follows: TEM positive: 61 (32.1%), SHV positive: 60 (31.6%) and CTX-M: 62 (32.6%). TEM, SHV and CTX-M genes occurred together in 25 (13.1%) of the isolates.
The high prevalence of E.coli producing ESBL in Boroujed hospitals reported. More than one ESBL was produced by many isolates, and this was correlated with increased resistance levels. Carbapenems continue to show good in vitro activity agent ESBLs producing organism.