Investigation of the prevalence and molecular epidemiology of CTX-M type extended spectrum beta-lactamase producers among enterobacteriaceae family isolated in different cities

Objectives: To investigate the prevalance, of CTX-M type beta-lactamases and properties of the genetic elements responsible for the spread of these among the members of Enterobacteriaceae family which are extended spectrum beta-lactamase positive and isolated from seven different hospitals between November 2002-July 2003. Clonal relationship between CTX-M producers was also evaluated. Methods: In this study blaCTX-M presence was sought by PCR in 70 isolates which are third-generation cephalosporin resistant and members of Enterobacteriacea family. Ten isolates per center were chosen randomly. Thirty two of these isolates were Esherichia coli, 24 were Klebsiella pneumoniae, three were Klebsiella ornitholytica, four were Enterobacter .cloacae, four were Enterobacter aerogenes, two were Proteus .mirabilis and one was Shigella sonnei. blaTEM ve blaSHV presence was also sought by PCR. Direct sequencing of CTX-M positive PCR-products was performed on both strands and CTX-M enzyme type was determined. Clonal relationship of CTX-M producers was investigated by ERIC-PCR. Genetic location of blaCTX-M was investigated by conjugation and plazmid extraction experiments. Results and Conclusion: blaCTX-M, blaTEM and blaSHV production rates were 75.7%, 81.4 %and 91.4%, respectively; among the study isolates species distribution of CTX-M producers was 77.4 % in E.coli, 83.3 % in K.pneumoniae, 50 % in E. aeogenes and E.cloacae isolates. The single S.sonnei isolate was also CTX-M positive. CTX-M prevalence varied between 50% (Uludağ University School of Medicine) to 100% (Hacettepe University School of Medicine) among centers. ERIC-PCR results revealed no clonal relationship between the isolates from different centers although there were clusters of two or three strains among isolates of a single center. Conjugation and plazmid analysis revealed that plazmids which had a molecular size of 46-85 kb were responsible from the transfer of blaCTX-M. Sequence analysis has shown that all of the CTX-M positive isolates included in this study produced CTX-M-3. As a result prevalance CTX-M type extended spectrum beta-lactamases is high among E.coli and K.pneumoniae isolates in our country. According to ERIC-PCR results however clonal dissemination of existence of an outbreak of CTX-M beta-lactamase producers between different centers is not considered.