Phenotypic and genotypic characterizations of extended-spectrum beta-lactamase-producing Escherichia coli in Thailand

Jiranun Bubpamala,1 Piyatip Khuntayaporn,1 Krit Thirapanmethee,1 Preecha Montakantikul,2 Pitak Santanirand,3 Mullika T Chomnawang1 1Department of Microbiology, Faculty of Pharmacy, Mahidol University, Bangkok, Thailand; 2Department of Pharmacy, Faculty of Pharmacy, Mahidol University, Bangkok, Thailand; 3Department of Pathology, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand Purpose: Extended-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 methods: In 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. Results: Of 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 bla CTX-M9 group (38.95%). The bla TEM, 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 bla CTX-M gene was mainly detected in all four ST-type E. coli clones (ST38, ST405, ST410, and ST131). Conclusion: This 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. Keywords: epidemiology, prevalence, antimicrobial resistance, MLST, ESBLs, antibiotic resistance gene