Abstract

Background: Bloodstream infections are recognized as important nosocomial infections. Escherichia coli (E. coli) is the most prevalent Gram-negative bacillary pathogen causing bloodstream infections (BSIs). This retrospective study investigated drug susceptibility and molecular epidemiology of E. coli isolated from patients with BSI in Shanghai, China.Methods: We collected E. coli isolated from the blood cultures of patients with BSI between January 2016 and December 2019. We randomly selected 20 strains each year to investigate antimicrobial resistance, resistance genes, and molecular epidemiological characteristics. Antimicrobial susceptibility testing was performed by the disk diffusion method. PCR was performed to detect extended-spectrum β-lactamases (ESBLs), carbapenemase genes, and housekeeping genes, and phyloviz was applied to analyze multilocus sequence typing (MLST).Results: Penicillins, first- and second-generation cephalosporins and fluoroquinolones have high resistance rates (>60%). Among the 80 randomly selected strains, 47 (58.8%) produced ESBLs, and one produced carbapenemase. Sequencing of resistance genes identified blaCTX−M−14 (34%, 16/47), blaCTX−M−15 (23.4%, 11/47) and blaCTX−M−27 (14.8%, 7/47) as the most prevalent genotypes of ESBLs. ST131 (14/80) was the most prevalent sequence type (ST), followed by ST1193 (10/80), ST648 (7/80).Conclusions: Our findings suggest that amikacin, carbapenems, and piperacillin-tazobactam have relatively low resistance rates and may be the preferred antibiotic regimens for empiric therapy. ST131 and blaCTX−M−14 are still the main prevalent in Shanghai with a rapid increase in the occurrence of ST1193 is rapidly increasing and more diverse blaCTX genes.

Highlights

  • Bacterial bloodstream infections are of global concern [1, 2]

  • The results showed that 47 isolates (58.8%, 47/80) were ESBLs-producing, and three isolates (3.75%) were resistant to carbapenems

  • There was a significant difference in resistance to cephalosporins between ESBL-producing and non-ESBL-producing isolates (P < 0.05) (Table 2)

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Summary

Introduction

Bacterial bloodstream infections are of global concern [1, 2]. They have been proven to be associated with high mortality rates, and are always accompanied by a prolonged hospital stay [3,4,5]. Escherichia coli was the most frequent Gram-negative bacterial pathogen according to a study of 264,901 BSIs collected from more than 200 medical centers in 45 countries between 1997 and 2016 [7]. We aimed to investigate antimicrobial resistance, resistance genes, and their relationship with the phylogenetic group and sequence type (ST) of causative bacterial pathogens isolated from BSI in Shanghai in the current clinical practice. Escherichia coli (E. coli) is the most prevalent Gram-negative bacillary pathogen causing bloodstream infections (BSIs). This retrospective study investigated drug susceptibility and molecular epidemiology of E. coli isolated from patients with BSI in Shanghai, China

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