Prevalence and antimicrobial resistance of Listeria species and subtyping and virulence factors of Listeria monocytogenes from retail meat

Abstract

In this study, of 124 samples of ground beef and chicken meat, 101 (81.5%) were positive for Listeria spp. Listeria innocua (35.5%) and Listeria monocytogenes (26.6%) were the most frequently isolated species. All 33 (100%) L. monocytogenes isolates were positive for the virulence genes hlyA, actA, inlA, inlB, inlC, inlJ, prfA, plcA, and iap. Serotype 1/2a, which is one of the listeriosis-associated serotypes, was the most predominant serotype (57.6%), followed by 1/2c (39.4%) and 3c (3%). In polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of inlA for subtyping of the L. monocytogenes strains, the AluI and MluCI enzymes generated two different profiles. Almost all chicken strains were grouped in similar PCR-RFLP profiles with both restriction enzymes. Most Listeria isolates were resistant to ceftriaxone (79.7%), fusidic acid (63.3%), and clindamycin (47.7%). Resistance to penicillin and ampicillin occurred in 1.6 and 17.9% of the isolates, respectively. The percentage of resistance to three or more agents was 48.1%. Practical application: The presence of Listeria spp., especially L. monocytogenes, in foods is inevitable because of the ubiquitous nature of Listeria spp. Illnesses resulting from the consumption of contaminated food severely affect sensitive groups, especially pregnant women, unborn fetuses and newborns as a result of transmission across the placenta or during delivery. Immunosuppressed adults are also sensitive to infection. Listeria grows well at cold temperatures, so storage of contaminated food in the refrigerator can also increase the risk of infections for consumers. In particular, limiting the exposure of pregnant women and immunosuppressed patients to potential sources of Listeria such as raw and undercooked meats is recommended.