Epidemiological investigation of CTX-M-producing Escherichia coli from retail livestock and chicken meat

Abstract:

[Objective] To investigate antibiotic resistance and epidemiological characteristics of bla_CTX-M gene of Escherichia coli from retail livestock and chicken meat in Guangzhou. [Methods] E. coli was isolated from retail livestock and chicken meat samples in different regional retail markets and fresh supermarket in Guangzhou. Those isolates were identified by the gene phoA and sequencing. Drug susceptibility was determined by agar diffusion and broth microdilution method. The bla_CTX-M gene was detected using PCR amplification. Whole genome sequencing was performed in all bla_CTX-M-positive E. coli.[Results] A total of 241 strains were isolated from 323 meat samples. The drug susceptibility test shows that those strains were highly resistant to ampicillin (63.07%), doxycycline (47.72%) and sulfamethoxazole/trimethoprim (43.15%). The prevalence of bla_CTX-M gene was 3.32% (n=8), which contained 4 bla_CTX-M-14-positive strains, 3 bla_CTX-M-65-positive strains and 1 bla_CTX-M-55-positive strain. Eight CTX-M-producing E. coli were divided into four distinct ST types, which carried multiple resistance genes and virulence genes.[Conclusion] The contamination of E. coli was serious in retail meat. All CTX-M-producing E. coli were multi-resistant strains, and the dissemination of bla_CTX gene was mainly due to horizontal transfer, which needs further surveillance.