Listeriosis is one of the most common bacterial zoonotic illnesses with significant death rate worldwide. The goal of this investigation was to ascertain the incidence and antibiotic resistance patterns of L. monocytogenes in various food items. In addition, an experiment was carried out to look at the anti-listerial properties of boiling and thyme oil. The isolation percentages of L. monocytogenes which confirmed by PCR using 16S rRNA gene were 10%, 3.3%, 6.6%, 13.3% and 3.3%, from the examined raw milk, beef burger, beef sausage, minced meat and chicken fillet meat samples respectively. The pathogenicity test by CAMP (Christie, Atkinson, Munch, Peterson) test indicated that all examined L. monocytogenes isolates were virulent. Serogrouping of isolated L. monocytogenes revealed that isolates belonged to (1/2a, 4b, 3c and 7) serotypes. The in-vitro antimicrobial sensitivity test showed that a high resistant rate for amoxicillin 9/11(81.8%), erythromycin 9/11 (81.8%), vancomycin 8/11 (72.7%), followed by doxycycline 7/11(63.6%), oxacillin 6/11(54.50%) and chloramphenicol 5/11(45.4%).The least resistance was found to be against gentamicin 4/11 (36.3%),sulfamethoxazole/trimethoprim 3/11(27.2%) and ciprofloxacin 3/11(27.2%). Molecular characterization of L. monoctogenes virulence genes showed that 63.6% harbored hlyA gene and 81.8% amplified InlA gene. It's interesting to note that L. monocytogenes was completely removed from experimentally contaminated milk after boiling it for three minutes. Additionally, adding 1% thyme oil to samples of contaminated chicken fillets reduces the amount of L. monocytogenes by log 2.13. They might be employed as substitute antibacterial aids in the food business because of their inhibitory activity.
Key words: L. monocytogenes , PCR, Virulence genes, Antimicrobial sensitivity.
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