PurposeExtended-spectrum β-lactamases (ESBLs) have become an issue in community worldwide due to an increase in antibiotic resistance over the past decade. This study was aimed to investigate the phenotypic and genotypic characteristics of ESBL-producing Escherichia coli in Thailand.Materials and methodsIn this study, all clinical isolates collected from tertiary hospitals in Thailand were identified as E. coli by biochemical tests and MALDI-TOF mass spectrometry. ESBL-producing E. coli was preliminary screened with disk diffusion method by cephalosporin disks and confirmed by the method of combination disk diffusion. Antimicrobial susceptibility test was used to determine MIC values of all ESBL-producing E. coli. For genotypic detection, a variety of ESBL genes were determined by PCR. Moreover, multilocus sequence typing (MLST) analysis was performed on internal portions of seven housekeeping genes for the diversity and phylogenetic relatedness of E. coli clonal group.ResultsOf the 285 ESBL-producing E. coli, most were susceptible to carbapenems. These strains showed a high resistance rate to ciprofloxacin (85.26%). The most frequently detected gene was bla CTX-M1 group at about 71.23% followed by blaCTX-M9 group (38.95%). The blaTEM, bla PER, bla GES, bla VEB, and bla SHV genes were identified in 31.93%, 5.96%, 4.56%, 3.51%, and 0.70% of ESBL-producing isolates, respectively. The bla OXA-10 gene was detected in only one strain. ESBL-producing E. coli isolates with high antimicrobial resistance were further investigated. Among those, E. coli sequence type ST38 was mostly found, followed by ST405, ST410, and ST131. It is noteworthy that the blaCTX-M gene was mainly detected in all four ST-type E. coli clones (ST38, ST405, ST410, and ST131).ConclusionThis study provided a recent evidence of the genetic diversity of ESBL-producing E. coli in Thailand. In addition, the profile related to antimicrobial resistance pattern in this region was also demonstrated.