Serotyping and antibiotic susceptibility of Listeria monocytogenes isolated from ready-to-eat foods in Samsun, Turkey

Abstract

The objective of the present study was to assess the presence of Listeria monocytogenes and to investigate its serotyping and antibiotic resistance in ready-to-eat (RTE) foods. A total of 100 RTE foods, including 25 stuffed mussels, 25 ezme samples (a Turkish-style tomato dip/condiment), 25 fried spiced livers, and 25 mayonnaise-based salads were obtained from retail shops and supermarkets in Samsun, Turkey. Samples were analyzed using the standard procedure EN ISO 11290-1 and isolates of L. monocytogenes were confirmed for the presence of the hemolysin gene (hylA) by polymerase chain reaction. L. monocytogenes was identified in 1 of 25 (4%) mayonnaise-based salads as serotype 4b, 2 of 25 (8%) ezme samples as serotype 1/2a, and 1 of 25 (4%) fried spiced livers as serotype 4b. None of the stuffed mussel samples were found to be contaminated with L. monocytogenes. Antibiotic resistance profiles of L. monocytogenes isolates were detected by the disk diffusion method. Eight antibiotics disks were selected for resistance tests. One of the 4 isolates of L. monocytogenes was resistant to oxytetracycline and 1 isolate was resistant to vancomycin. In conclusion, the presence of L. monocytogenes serotypes 4b and 1/2a in RTE foods is of significant concern for public health as these serotypes are predominant serotypes that can cause listeriosis in humans.