Molecular characterization of nosocomial CTX-M type ß–Lactamase producing Enterobacteriaceae from University Hospital in Turkey

Extended-spectrum s–Lactamase (ESBL) producing members of the Enterobacteriaceae family are important nosocomial pathogens. CTX-M type extended-spectrum s–Lactamases (ESBLs) are now the most important cause of resistance to beta-lactam antibiotics in Escherichia coli and are reported worldwide with increasing frequency. Dominant CTX-M genotype varies geographically. CTX-M 15 dominates in many countries including the UK and India whereas CTX-M 2 is the most common genotype in Latin America while CTX-M 9 and CTX-M 14 is common in Spain and Far East. In this study, a total of 100 consecutive ESBL positive nosocomial isolates of Enterobacteriaceae collected from Afyon Kocatepe University Hospital were screened for production of ESBLs by double disk synergy test and the susceptibility to antibiotics was determined. Then this results was confirmed by Phoenix® (Bekton Dickinson Diagnostics) and MicroScan®(Dade Behring Inc.). Among 100 ESBL positive strains, 65 were positive for CTX-M by polymerase chain reaction (PCR) with universal primers. However, when group specific primers were used, 63 strains were positive for CTX-M 1 (63.0%), 1 strain was positive  for CTX-M 2 (1%) and 1 strain was positive for CTX-M 9 (1%). PCR detected bla (CTX-M) in 50/82 (60,97%) E. coli, 12/14 (85.71%) Klebsiella pneumoniae and 1/2 (50.0%)Citrobacter freundii isolates with the ESBL phenotype. But there was no positive isolate detected in Morganella morganii and Enterobacter cloacae. Amplicons were sequenced to determine the CTX-M types and sequences were compared to gene bank. Among CTX-M 1 positive strains sequence, results showed higher homology to CTX-M 15 (31 strains), CTX-M 28 (17 strains), CTX-M 3 (9 strains), CTX-M 22 (2 strains), CTX-M 33 (2 strains) and CTX-M 42 (2 strains). As a result, the most common CTX-M type was CTX-M 15, the second common CTX-M type was CTX-M 28 related among strains isolated in Afyonkarahisar Turkey. Further studies will be necessary to confirm our findings.   Key words: Enterobacteriaceae, extended-spectrum s–Lactamase (ESBLs), blaCTX-M, blaCTX-M 1, extended spectrum β-Lactamase, polymerase chain reaction (PCR), sequencing.