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.