The Characteristics of Extended-Spectrum ?-Lactamases (ESBLs)-Producing Escherichia coli in Bloodstream Infection

Background: Bloodstream infection (BSI) is a common type of infection frequently diagnosed in clinics. The emergence and spread of ESBLs-producing Escherichia coli (E. coli) has emerged as one of the biggest challenges in global community health. Methods: The production of ESBLs was determined by the composite disk diffusion method. The expression of the various resistance and virulence genes were detected by PCR and sequencing. Multi-locus sequence typing (MLST) and phylogenetic groups were used for the classification. The transfer of resistant plasmids was determined by conjugation assay. The statistical differences were analyzed using Statistical Product and Service Solutions (SPSS) version 23.0. Results: A total of 60 strains of ESBLs-producing E. coli were collected. The resistance genes that were identified included blaCTX-M, blaTEM, blaSHV, blaOXA-1 and mcr-1. The most common one was the blaCTX-M including blaCTX-M-27 (n = 16), blaCTX-M-14 (n = 15), blaCTX-M-15 (n = 11), blaCTX-M-55 (n = 14) and blaCTX-M-65 (n = 5). A total of 31 STs were detected, and the most abundant among which was ST131 (n = 16, 26.7%). Most of the E. coli (n = 46, 76.7%) belonged to the groups B2 and D. And some virulence genes were related to the classification of the E. coli. Among them, the detection rates of hek/hra, kpsMII and papGII-III in groups B2 and D were higher than those in groups A and B1. The detection rates of cnf1, iucC and papGII-III in ST131 were higher than those in non-ST131. And the distributions of hek/hra, iroN, iucC, kpsMII and papGII-III were related to the blaCTX-M subtypes. Finally, most bacterial (n = 32, 53.3%) resistance genes could be transferred between the bacteria by plasmids, especially IncFIB. Conclusion: ESBLs-producing E. coli in BSI exhibited had high resistance rates and carried a variety of virulence factors (VFs). This is necessary to strengthen the monitoring of ESBLs-producing isolates in the medical environment.

Automated summary

This study investigated the resistance and virulence characteristics of ESBLs-producing Escherichia coli in bloodstream infections. The results showed that the most common resistance gene was blaCTX-M, the most common multi-locus sequence typing was ST131, and there was a correlation between the classification of E. coli and specific virulence factors. Most resistance genes could be transferred between bacteria through plasmids. Therefore, it is necessary to strengthen the monitoring of ESBLs-producing isolates in the medical environment.