The characterization and antibiotic resistance profiles of clinical Escherichia coli O25b-B2-ST131 isolates in Kuwait

BACKGROUND: Escherichia coli O25b-B2-ST131 are considered virulent extra-intestinal pathogens causing serious clinical complications such as urinary tract infection and bacteraemia. Our main objectives in this study were to characterise the multi-drug resistant (MDR) isolates of this lineage in Kuwait, and to demonstrate whether reduced susceptibility is spread clonally. RESULTS: A subset of 83 (10%) non-duplicate and non-selective E. coli O25b-B2-ST131 out of 832 MDR E. coli was identified and collected. Minimum inhibitory concentrations of the isolates were determined and pulsed-field gel electrophoresis was used for typing. The majority (95.2%) of the 83 E. coli O25b-B2-ST131 harboured at least one bla gene with bla(CTX-M-15) being the most prevalent. bla(CTX-M-2) was present in one isolate. Also one isolate harboured bla(CTX-M-56), qnrB1 and bla(CMY-2) genes and carried IncF1 plasmids of about 97 kb and160 kb. qnrB and qnrS were found in 8 other bla(CTX-M-15) containing isolates. The bla(NDM), bla(IMP), bla(VIM) and qnrA were not detected, however, the bla(OXA-48) was present in two (2.4%). CONCLUSIONS: The majority of isolates harbouring qnr genes demonstrated relatedness (≥85%) by PFGE. However, the diversity in PFGE profiles for the other MDR isolates reflected the changes in population genetics of E. coli O25b-B2-ST131. We identified for the first time the appearance of bla(CTX-M-2) in the Middle East and bla(CTX-M-56) outside the Latin American countries. The isolate harbouring bla(CTX-M-56) also contained qnrB1 and bla(CMY-2) genes and carried IncF1 plasmids. The appearance of a highly virulent E. coli O25b-ST131 that is resistant to penicillins, most cephalosproins, β-lactamase inhibitors as well as fluoroquinolones is a cause for concern. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12866-014-0214-6) contains supplementary material, which is available to authorized users.