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Updated: Sep 16, 2026

Isolation and Identification of Waterborne Antibiotic-Resistant Bacteria and Molecular Characterization of their Antibiotic Resistance Genes
Published on: March 3, 2023
Epidemiology and molecular characterization of CTX-M-type ESBLs producing Escherichia coli isolated from clinical
Keyi Yu1, Zhenzhou Huang2, Yue Xiao1
1National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention (China CDC), State Key Laboratory of Infectious Disease Prevention and Control, Beijing, 102206, China; Center for Human Pathogenic Culture Collection, China CDC, Beijing, 102206, China.
Objectives:
Recently, blaCTX-Ms have become the dominant ESBLs for E. coli strains worldwide. We aim to provide a systematic study on the relationships between sequence types (STs), clinical origins, and the blaCTX-Ms genotypes of E. coli strains.
Methods:
Totally, 1005 complete sequences of clinical E. coli were collected from NCBI. Multilocus sequence typing (MLST) and antibiotic resistance genes screening were performed.
Results:
Faeces (26.27%), urine (16.02%), and blood (8.26%) were shown to be the main sources of clinical E. coli isolates. The isolates belong to 153 STs and 26 clonal complexes (CCs). The most prevalent STs were ST2 (11.3%), ST43 (8.6%), and ST8 (5.7%). The positive rate for blaCTX-Ms was 34.7%. Different samples showed significantly different blaCTX-Ms positive rates (P<0.05). The main genotypes were blaCTX-M-55-like (47.6%), blaCTX-M-1-like (31.8%), and blaCTX-M-2-like (22.1%). The majority of ST2 strains had blaCTX-M-55-like genes. In ST8 strains, there was a homogeneous distribution of blaCTX-M-9, blaCTX-M-65, blaCTX-M-55, blaCTX-M-2, and blaCTX-M-1. Only ST43 strains exhibited the presence of blaCTX-M-79. The blaCTX-Ms showed a pattern of cross-continental transmission with intra-regional spread. Among the 349 blaCTX-Ms-producing E. coli strains, 148 strains also carried carbapenem resistance genes, including blaNDM (119, 34.1%), blaKPC (16, 4.6%), blaOXA-48 (9, 2.6%) and blaIMP (4, 1.1%). Also, 81 strains carried the mcr gene (23.2%).
Conclusions:
E. coli has become increasingly rich in blaCTX-Ms genotypes. Our findings about the connection between E. coli STs and blaCTX-Ms can be utilized to identify E. coli strains with high potential to spread drug resistance in the future.
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