Antimicrobial activity of Escherichia coli from retail meat in Guangzhou

Objective  To understand the contamination status and antimicrobial activity of Escherichia coli in retail meat sold in Guangzhou.

Method  We collected 310 meat samples including 253 retail pork and 57 chicken meat from markets and supermarkets in Guangzhou from July to August, 2011. E.coli strains were isolated and identified using the selective media. The susceptibilities of E.coli strains to 19 common antibiotics represented by the minimum inhibitory concentrations (MIC) were tested using the agar dilution method.

Result  Totally 213 E. coli strains were isolated from 310 meat samples with the detection frequency of 68.7%, including 117 pork isolates and 36 chicken meat isolates. More than 75.0% isolates were resistant to sulfamethoxazole/trimethoprim, streptomycin and tetracycline, 10.0% to 60.0% isolates were resistant to ampicillin, nalidixic acid, chloramphenicol, neomycin, florfenicol, fosfomycin, ciprofloxacin, apramycin, enrofloxacin, gentamicin and cefazolin, and the isolates were sensitive to cefoxitin, ceftriaxone, ceftazidime, colistin and amikacin with below 5.0% being resistant strains. Isolates from chicken meat showed significantly higher resistance to cefazolin, cefoxitin, ceftriaxone, ceftazidime and fosmycin compared to pork isolates(P < 0.01). There were 82.2% multi-drug resistant strains of 213 E. coli strains.

Conclusion  Retail meat sold in Guangzhou were severely contaminated by multi-drug resistant E. coli, and chicken meat isolates showed higher resistance compared to pork isolates.