Prevalence of extended-spectrum β-lactamase-producing Escherichia coli in various animal-derived food products

Abstract

Various strains of Escherichia coli are significant foodborne pathogens that can threaten public health through contaminated food. In this study, a total of 217 animal-derived food products, including raw turkey meat, raw beef, fresh cheese, and raw milk, were collected from markets, butcher shops, dairies, and neighborhood markets in Istanbul during 2021, 2022, and 2023. E. coli isolates were detected in 13.4% of the samples using conventional microbiological methods, and identification was confirmed by PCR targeting the E. coli -specific 16S rRNA gene region. The proportions of E. coli isolated were: 26.1% from raw turkey meat, 15.4% from raw beef, 8% from raw milk, and 0% from fresh cheese. The isolates were further analyzed by PCR for the presence of stx1 , stx2 , and rfbO157 genes; none of the isolates carried these virulence genes. Antibiotic susceptibility testing by the disk diffusion method revealed resistance rates of 93.1% to ampicillin; 62% to ceftazidime, cefotaxime, amoxicillin/clavulanate, and chloramphenicol; and 55.1% to meropenem. Multidrug-resistant E. coli isolates accounted for 75.8% of the total, and 51.7% were identified as extended-spectrum β -lactamase producers by the double-disk synergy test. PCR analysis showed that 82.7% of isolates carried the bla TEM gene. The mPCR method was used to detect bla CTX-M and yielded positive results in 6.8% (2/29) of group 1, 65% (19/29) of group 2, 10% (3/29) of group 8 and 25/26, and 13.7% (4/29) of group 9. No carbapenemase or mobilized colistin resistance genes were detected. In this study, the biofilm-forming capacity of E. coli isolates was measured using a microplate method; notably, 75% of the raw milk-derived isolates formed biofilms in Brain Heart Infusion Broth. The results of this study indicate that antibiotic resistance rates in foodborne E. coli isolates are at alarming levels for public health, and that immediate preventive measures should be taken.