Molecular identification of Methicillin-resistant staphylococcus aureus (MRSA) and Vancomycin- resistant staphylococcus aureus (VRSA) strains isolated from milk and milk products.

Keywords In developing countries, resistance to antimicrobial agents is a serious public health problem, and the indiscriminate use of antimicrobials is a key contributor to the development of resistant bacterial diseases. The following research was aimed to determine the in-vitro antimicrobial activity of (23 strains) of Staphylococcus aureus isolated from 80 random samples of milk and dairy products (soft cheese “Kareish and white” and Roomy cheese) 20 samples from each product, with molecular identification of their resistant genes. The results declared that all isolated strains were totally resistant to Ampicillin (100%), Amoxicillin, and Erythromycin (86.9%), then Oxacillin (65.2%), while all other strains showed intermediate susceptibility to Vancomycin, Cefoxitin, Cefotaxime, and Norfloxacin. While Gentamicin had the highest level of susceptibility (78.3%). Moreover, by the cultivation of the isolated strains on oxacillin resistance screening agar base plates “ORSAB,” there were 15/23 MRSA strains; also, 5/23 strains showed resistance to Vancomycin and grow well in vancomycin screening agar. The molecular identification for the mecA gene and vanA gene was made on seven strains (3 strains resistant to both Oxacillin and Vancomycin, two strains with intermediate resistance, and two strains sensitive to them) isolated from different products (milk, Kariesh cheese, soft white cheese, and Roomy cheese). The results showed that all the samples carried the mecA gene, while only two samples had the vanA gene (isolated from milk). Staphylococcus aureus Antimicrobial resistant mecA gene vanA gene