Drug susceptibility and molecular epidemiology of Escherichia coli in bloodstream infections in Shanghai, China, 2011–2013

Abstract

Background: Prevention and management of Escherichia coli bloodstream infections (EC-BSIs) have become increasingly complicated by antimicrobial resistance and rapid dissemination. We investigated the antimicrobial epidemiology and phylogenetic background of clinical E. coli isolates from patients with bloodstream infections in Shanghai from 2011 to 2013. Methods: Escherichia coli isolates causing bloodstream infections were consecutively collected between June 2011 and June 2013. Antimicrobial susceptibility testing was performed by disk diffusion. Drug resistance genes coding for extended-spectrum β-lactamases (ESBLs) and carbapenemases, and phylogenetic groups were detected by polymerase chain reaction. eBURST was used for multilocus sequence typing. Results: Of the strains 128 collected, 80 produced ESBLs. No carbapenem-resistant isolates were found. The resistance rates to penicillins, fluoroquinolone, folate pathway inhibitors, tetracyclines and second generation cephalosporins were high. Molecular analysis showed that CTX-M-14 (40/80) was the most common β-lactamase, followed by CTX-M-55 (17/80) and CTX-M-15 (14/80). Phylogenetic group B2 predominated (37.5%), but phylogenetic group D exhibited the highest rates of ESBL production. ST131 (17/128) was the most common sequence type, followed by ST69 (12/128) and ST648 (10/128). Conclusions: The antimicrobial resistance rate was high among EC-BSI isolates, but amikacin, piperacillin–tazobactam and carbapenem could be options for empiric therapy. Genetic diversity showed no correlation with the nosocomial origin of the isolates.

Keywords::

• Antimicrobial resistance
• bloodstream infections
• Escherichia coli
• phylogenicity

Acknowledgements

We would like to thank the Department of Medical Microbiology and Parasitology at the School of Medicine of Shanghai Jiao Tong University for excellent laboratory provision and technical assistance, and Li Linhui for the preparation of the isolates.

Declaration of interest: This work was supported by the Special Fund for Health-scientific Research in the Public Interest of China Program (grant no. 201002021). The authors declare that they have no potential conflicts of interest.