LISTERIA MONOCYTOGENESIN RAW MILK AND DAIRY PRODUCTS;OCCURRENCE AND TRIALS FOR THEREDUCTION OF THEIR RESISTANCE TO ANTIBIOTICS

Listeria monocytogenes is a facultative intracellular pathogen responsible for severe infection in animals and humans. This study aimed to determine the occurrence of Listeriamonocytogenes in 200 samples of raw milk and dairy products marketed in Egypt, with detection the antimicrobial resistance profiles of the isolates for different antimicrobial agents. The synergistic effects of three plant extracts in combination with the used antimicrobials to control resistant L. monocytogenes isolates were assessed, with evaluation of relationship between the antibacterial activity and composition of plant extracts. A total of 5 (2.5%) L. monocytogenes isolates were identified (3 isolates from raw milk and two isolates from kariesh cheese and ice cream, one each). The isolates were sensitive to ciprofloxacin and sulphadimidine, while for amoxicillin and oxytetracycline, were resistant. The higher antimicrobial effects of basil and cinnamon extracts were detected, in addition, low concentrations of them were enough to show synergistic effect with the amoxicillin and oxytetracycline to control resistant isolates, these might be attributable to their chemical compositions. In conclusion, there is need for effectively pasteurized raw milk consumption or usage in the production of dairy products. In addition, the chemical composition of these plant extracts might help in its use to control resistant isolates with appropriate antibiotics without the need for increasing the used dosage doses.