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Background <p>Bloodstream infections (BSIs) caused by <i>Escherichia coli</i> represent a major clinical challenge, particularly among elderly patients and those with urinary catheters. The rising prevalence of extended-spectrum β-lactamase (ESBL)-producing strains further complicates therapeutic management and infection control. This study aimed to characterize the clinical features, antimicrobial resistance profiles, and genomic features of ESBL-producing <i>E. coli</i> isolates associated with BSIs in a county-level hospital in Zhejiang Province, China.</p> Methods <p>A total of 236 non-duplicate <i>E. coli</i> isolates recovered from BSIs were collected between January 2021 and December 2023. Antimicrobial susceptibility testing (AST) was performed for all isolates. Of these, 144 isolates were successfully preserved for subsequent molecular analysis, among which 65 ESBL-producing isolates underwent whole-genome sequencing (WGS) for the detection of ESBL genes, phylogenetic grouping, multilocus sequence typing, serotyping, <i>fimH</i> typing, and core genome SNP analysis.</p> Results <p>Most patients were elderly women, and urinary tract infection was identified as the primary source of bacteremia. Resistance rates were low to piperacillin-tazobactam (2.14%) and cefoperazone-sulbactam (1.28%) but high to levofloxacin (35.74%), ceftriaxone (47.01%), cefuroxime (50.21%), and trimethoprim-sulfamethoxazole (56.17%); all isolates remained fully susceptible to imipenem, ertapenem, amikacin, and tigecycline. Among 144 isolates, 65 (45.1%) were ESBL producers, predominantly carrying <i>bla</i><sub>CTX−M−27</sub>, followed by <i>bla</i><sub>CTX−M−14</sub>, <i>bla</i><sub>CTX−M−55</sub>, and <i>bla</i><sub>CTX−M−15</sub>. Phylogenetic analysis showed that the majority of ESBL-producing isolates were assigned to phylogroups B2 and D, with ST131 as the dominant sequence type, strongly associated with O25:H4 and <i>fimH30</i>. Core genome SNP analysis revealed substantial genetic diversity, with closely related isolates mainly observed within the same patient over time.</p> Conclusions <p>This study highlights a substantial burden of ESBL-producing <i>E. coli</i> BSIs, dominated by the ST131-<i>fimH30</i>-O25:H4 clone carrying <i>bla</i><sub>CTX−M−27</sub>, underscoring the need for enhanced surveillance, targeted antimicrobial therapy, and effective infection control strategies.</p>

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Genomic characterization of extended-spectrum β-Lactamases (ESBLs)-producing Escherichia coli recovered from bloodstream infections in China

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  • 发表日期：

    2026年4月14日

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  • Danni Bao,
  • Xiaohong Xu,
  • Yizhang Wang,
  • Yanhong Wu,
  • Tingfei Chen,
  • Jiayu Shao,
  • Fengjiao Zhu,
  • Huiying Ye,
  • Hongzhang Li

摘要

Background

Bloodstream infections (BSIs) caused by Escherichia coli represent a major clinical challenge, particularly among elderly patients and those with urinary catheters. The rising prevalence of extended-spectrum β-lactamase (ESBL)-producing strains further complicates therapeutic management and infection control. This study aimed to characterize the clinical features, antimicrobial resistance profiles, and genomic features of ESBL-producing E. coli isolates associated with BSIs in a county-level hospital in Zhejiang Province, China.

Methods

A total of 236 non-duplicate E. coli isolates recovered from BSIs were collected between January 2021 and December 2023. Antimicrobial susceptibility testing (AST) was performed for all isolates. Of these, 144 isolates were successfully preserved for subsequent molecular analysis, among which 65 ESBL-producing isolates underwent whole-genome sequencing (WGS) for the detection of ESBL genes, phylogenetic grouping, multilocus sequence typing, serotyping, fimH typing, and core genome SNP analysis.

Results

Most patients were elderly women, and urinary tract infection was identified as the primary source of bacteremia. Resistance rates were low to piperacillin-tazobactam (2.14%) and cefoperazone-sulbactam (1.28%) but high to levofloxacin (35.74%), ceftriaxone (47.01%), cefuroxime (50.21%), and trimethoprim-sulfamethoxazole (56.17%); all isolates remained fully susceptible to imipenem, ertapenem, amikacin, and tigecycline. Among 144 isolates, 65 (45.1%) were ESBL producers, predominantly carrying blaCTX−M−27, followed by blaCTX−M−14, blaCTX−M−55, and blaCTX−M−15. Phylogenetic analysis showed that the majority of ESBL-producing isolates were assigned to phylogroups B2 and D, with ST131 as the dominant sequence type, strongly associated with O25:H4 and fimH30. Core genome SNP analysis revealed substantial genetic diversity, with closely related isolates mainly observed within the same patient over time.

Conclusions

This study highlights a substantial burden of ESBL-producing E. coli BSIs, dominated by the ST131-fimH30-O25:H4 clone carrying blaCTX−M−27, underscoring the need for enhanced surveillance, targeted antimicrobial therapy, and effective infection control strategies.