Rahman Mirzaei - Department of Food Hygiene, Ayatollah Amoli Branch, Islamic Azad University, Amol, Iran.
Leila Golestan - Department of Food Hygiene, Science and Research Branch, Islamic Azad University, Tehran, Iran
Zahra Fekrirad - Department of Biology, Faculty of Basic Sciences, Shahed University, Tehran, Iran.Rahman

L. monocytogenes is a significant foodborne pathogen that is associated with clinical illnesses ranging from self-limited gastroenteritis to invasive infection leading to hospitalization of immunocompromised people. Thus, in the current study, the incidence of this bacteria was measured in the RTE food of Tehran, Iran.۱۱۰ samples were collected from ready-to-eat (RTE) foods from different zones of Tehran from April until September ۲۰۲۲. The samples were from Caesar salad, Olivier salad, Burger, Schnitzel, Sushi, and Sausage. Isolates were identified by detecting hlyA and prfA genes applying PCR i.e., polymerase chain reaction. The antimicrobial resistance profile of isolates was assessed through disc diffusion assay and PCR amplification of resistance genes. Fourteen among ۱۱۰ samples (۱۲.۷%) were known to be Listeria spp. and six samples (۵.۵%) were L. monocytogenes. using molecular methods. schnitzel and burgers had the highest rate of Listeria spp. with ۳۰% of schnitzel and ۲۵% of burger samples. Among ۱۴ isolates, ۶ samples (۴۲%) were characterized as L. monocytogenes Burgers showed the highest rate of L. monocytogenes which was ۲۰% of total burger samples; Caesar Salad, Sausage, and Sushi samples contained no identified L. monocytogenes.The isolated L. monocytogenes show resistance against oxacillin, streptomycin, cotrimoxazole, clindamycin, and cefoxitin and are susceptible to chloramphenicol. Isolates were semi-susceptible to fosfomycin and ampicillin. The isolates resistant to erythromycin contain genes involved in resistance to the macrolide class of antibiotics (ermA and ermB). cfxA and mecA genes were only detected in one of the isolates resistant to cefoxitin and oxacillin. Overall, there is considerable concern about listeriosis threatening ready-to-eat (RTE) food consumers.

Listeria monocytogenes, Ready to eat, antimicrobial resistance, PCR amplification, Virulence gene