2023 Volume 40 Issue 4 Pages 122-128
The definition of EASTEC refers to Escherichia coli strains lacking any well-established diarrheagenic factors except for the enteroaggregative E. coli (EAggEC) heat-stable toxin 1 gene (astA). However, the causative food source has often remained unidentified in these outbreaks, possibly due to the lack of appropriate detection methods for EASTEC in food products. To address this issue, we conducted a study comparing different strains of EASTEC O166:H15, the most common serotype, with varying origins, and investigated the usefulness of various culture and screening methods, including real-time PCR. We found that the growth of all tested strains was suppressed on agar containing cefixime-tellurite supplement or 2 mg/L tobramycin, but not on agar with 1 mg/L tobramycin. In the additive recovery test, CHROMagar STEC with 1 mg/L tobramycin and SMAC with 1 mg/L tobramycin showed relatively high detection rates. Furthermore, real-time PCR of the inoculum showed a detection sensitivity of 1.00 (20/20) under all enrichment culture conditions, with Ct values around 20. Based on our results, we conclude that a combination of the culture method using tobramycin-added selective agars and screening by real-time PCR may be an efficient and effective method for detecting EASTEC in food products.
