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Extended spectrum β‐lactamase producing Escherichia coli (ESBL‐EC) was detected in 86.6% of chicken and 22.6% of bulk tank milk (BTM) samples. Pulsed‐field gel electrophoresis analysis revealed 49 distinct restriction profiles among 66 isolates, and 62.3% of the isolates carried the blaCTX‐M gene, among which CTX‐M‐1 was found to be the predominant ESBL types in chicken isolates, whereas CTX‐M‐15 was the commonest among BTM samples. Additionally, of 52 ESBL‐EC isolates from chicken meat samples, 36.5%, 9.6%, and 7.7% harbored the blaTEM, blaCMY‐2, and blaSHV‐12 genes, respectively, compared with 28.5% of the blaTEM and 7.1% of the blaSHV‐12 markers among BTM isolates. The fimH gene was present in 51 isolates of chicken and in 14 isolates of BTM samples, while other virulence genes iutA (n = 31), iroN (n = 26), kpsMT II (n = 5), papC (n = 2), papG allele II (n = 2), papG allele II‐III (n = 2), and papEF (n = 2) were only present in chicken meat isolates. Overall, it can be said that contaminated chicken meat and BTM might serve as vehicles for playing potential role in zoonotic transmission of ESBL‐EC to humans in Turkey. Practical applications Extended spectrum β‐lactamase producing E. coli (ESBL‐EC) have been considered to be one of the major worldwide clinical problems and have been frequently isolated from the foods of animal origins such as chicken meat, fish, and raw milk. The current study aimed to isolate ESBL‐EC from chicken and bulk tank milk samples and further characterize the strains by PFGE, identifying resistance genes and as well as virulence genes. Given the high prevalence of CTX‐M‐15/55 type ESBL‐EC strains possessing important virulence genes in chicken and milk samples, it can be said that foods of animal origins might be an important risk factor for extraintestinal ESBL‐EC infections for humans.

Escherichia coli O157:H7 is a major foodborne pathogen that has posed serious problems for food safety and public health. Recent outbreaks and recalls associated with various foods contaminated by E. coli O157:H7 clearly indicate its deleterious effect on food safety. A rapid and sensitive detection assay is needed for this harmful organism to prevent foodborne illnesses and control outbreaks in a timely manner. We developed a magnetic bead-based immunoassay for detection of E. coli O157:H7 (the most well-known Shiga toxigenic E. coli strain) with a 96-well microplate as an assay platform. Immunomagnetic separation (IMS) and tyramide signal amplification were coupled to the assay to increase its sensitivity and specificity. This immunoassay was able to detect E. coli O157:H7 in pure culture with a detection limit of 50 CFU/ml in less than 3 h without an enrichment step. The detection limit was decreased 10-fold to 5 CFU/ml with addition of a 3-h enrichment step. When this assay was tested with other nontarget foodborne pathogens and common enteric bacteria, no cross-reactivity was found. When tested with artificially contaminated ground beef and milk samples, the assay sensitivity decreased two- to fivefold, with detection limits of 250 and 100 CFU/ml, respectively, probably because of the food matrix effect. The assay results also were compared with those of a sandwich-type enzyme-linked immunosorbent assay (ELISA) and an ELISA coupled with IMS; the developed assay was 25 times and 4 times more sensitive than the standard ELISA and the IMS-ELISA, respectively. Tyramide signal amplification combined with IMS can improve sensitivity and specificity for detection of E. coli O157:H7. The developed assay could be easily adapted for other foodborne pathogens and will contribute to improved food safety and public health.

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