MOLECULAR DETECTION OF VIRULENCE GENES FOR LISTERIA MONOCYTOGENES ORGANISM ISOLATED FROM RAW MILK AND SOME LOCALLY MADE MILK PRODUCTS

SADEK, O.A.; KORIEM, A. M.; AL-HABATY, S.H.; ABDEL HAMEED, ZEINAB M.

doi:10.21608/avmj.2024.303681.1302

MOLECULAR DETECTION OF VIRULENCE GENES FOR LISTERIA MONOCYTOGENES ORGANISM ISOLATED FROM RAW MILK AND SOME LOCALLY MADE MILK PRODUCTS

Document Type : Research article

Authors

¹ Department of Food Hygiene, Assiut Provincial Lab., Animal Health Research Institute, Agricultural Research Center (ARC), Egypt.

² Bacteriology Department, Assiut Provincial Lab., Animal Health Research Institute, Agricultural Research Center (ARC), Egypt.

10.21608/avmj.2024.303681.1302

Abstract

This study was designed to find out the prevalence of Listeria monocytogenes in raw milk and some dairy products and the molecular identification of their virulence genes. One hundred and twenty samples in all, including milk, Kareish cheese, and yogurt (40 of each), were gathered randomly from various sources for this study and examined for the presence of Listeria monocytogenes. Eight distinct strains of L. monocytogenes were identified and molecularly examined for 16 srRNA-specific genes for Listeria monocytogenes, as well as the identification of many pathogenicity genes (inlA, inlB, hlyA, and prfA genes). All eight isolates harbored 16srRNA-specific genes for Listeria monocytogenes; seven isolates harbored both inlA and inlB; six isolates harbored hlyA; and five isolates harbored the prfA gene. The results of antimicrobial susceptibility testing showed high sensitivity to Ciprofloxacin (CP), Gentamycin (CN), Vancomycin (VA), Doxycycline (DO), and Trimethoprim-sulfamethoxazole (SXT) with 100, 87.5, 87.5, 78.5, and 62.5%, respectively, while showing high resistance to Ampicillin (AM), Amoxicillin (AX), Oxicillin (OX), Erythromycin (E), Lincomycin (L), and Ceftriaxone (CRO) with 100, 100, 100, 100, and 75%, respectively. All eight Listeria monocytogenes isolates were multidrug-resistant, holding a variety of antibiotic resistance indexes (MARI) in the range of 0.417–0.833. In conclusion, the study's findings highlight the necessity of implementing more stringent sanitary control procedures, particularly while processing, storing, and marketing dairy products. The pasteurization temperatures must not be less than 85 °C, where only 85% of the bacteria are destroyed by pasteurization at 71–75 °C for 15 seconds.

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