Genomic Characterization and Antimicrobial Resistance of ESBL-Producing, Escherichia coli Isolates in Suzhou, China.

Background: The prevalence of third-generation cephalosporin-resistant and extended-spectrum beta-lactamases (ESBL) producing Escherichia coli poses a significant global public health concern due to their resistance to multiple antibiotics; however, their prevalence and epidemiological patterns in China are not very well investigated.

Objective: This study aimed to investigate the molecular epidemiology, and antimicrobial susceptibility of ESBL-producing E. coli among clinical isolates in China.

Methods: Phenotypic ESBL-producing E. coli isolates were collected from in-patients at a non-tertiary hospital in Suzhou from 2018.06.01 -2019.11.30. All isolates were identified and analyzed by conventional microbiological methods, and antimicrobial susceptibility testing was determined. Genes associated with resistance to β-lactamases, fluoroquinolone, aminoglycosides, sulfonamides, sequence types (STs), and genetic relationship were characterized through whole-genome sequencing (WGS) data.

Results: Eighty-six isolates were collected and sequenced, and genomic analysis identified twenty-five different sequence types (STs). The most prevalent STs were ST131 (n=22, 25.6%), ST1193 (n=16, 18.6%), ST38 (n=9, 10.5%) and ST167 (n=6, 7.0%). blaCTX-M genotypes were the most dominant, comprising a variety of subtypes (eg, blaCTX-M-14, blaCTX-M-15, blaCTX-M-27, blaCTX-M-55) and blaTEM-type among ESBL-producing E. coli in our study. All cases of co-carriage of β-lactamase genes showed a strong link to amoxicillin/sulbactam resistance, while the co-carriage of blaCTX-M-15/TEM-1B or blaCTX-M-15/OXA-1 were strongly linked to resistance against cefepime, ceftazidime, and aztreonam. In addition, genes associated with resistance to fluoroquinolone, aminoglycosides, and sulfonamides were also detected.

Conclusion: Our findings highlighted the prevalence of globally circulating ESBL-producing E. coli clones, such as ST131 and ST1193, in Suzhou, China. These clones and sublineages are also resistant to quinolones. No predominant blaCTX-M subtypes were detected, while the coexistence of different ESBL types was strongly linked to resistance to amoxicillin/sulbactam, cefepime, ceftazidime, and aztreonam, suggesting the widespread circulation of diverse blaCTX-M genes within the Suzhou community. In clinical cases of ESBL resistance, carbapenem therapy is recommended as most (>90%) isolates were susceptible.