Sequence Analysis of blaCTX-M Genes Carried by Clinically Significant Escherichia coli Isolates in Kuwait Hospitals

Objective: To investigate the extent, distribution and sequence analysis of blaCTX-M genes carried by Escherichia coli isolated from patients admitted to all government hospitals in Kuwait. Methods: Extended-spectrum β-lactamase (ESBL)-producing E. coli isolates were collected from the 8 major hospitals in Kuwait. CTX-M ESBLs were analyzed by PCR and sequenced. Clonality of the positive isolates was determined for genetic relatedness using pulsed-field gel electrophoresis (PFGE) with XbaI digestion of the genomic DNA. Results: Of the 136 ESBL-positive isolates, 106 (77.9%) harbored blaCTX-M genes. Among these, blaCTX-M-15 was the most frequent with a prevalence rate of 84.1%, followed by blaCTX-M-14 (6.8%), blaCTX-M-14b (5.7%) and blaTOHO-1 (3.4%). Ninety-three (87.7%) were isolated from Kuwaiti (35.9%), Egyptian (31.1%) and Indian (20.8%) nationals; the majority of isolates positive for blaCTX-M-15 were mainly from these 3 nationalities. PFGE analysis did not demonstrate any clustering of positive isolates in any particular hospital. Conclusion: This study confirms an explosive emergence of CTX-M-15 β-lactamase among E. coli isolates in Kuwait and shows that the strains were clonally heterogeneous with no evidence of inter- or intra-hospital spread. Thus Kuwait may represent an important source of CTX-M-15-positive E. coli.