الفهرس 
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Abstract
ABSTRACT
Staphylococcus aureus is a dominant pathogen of food poisoning which may cause life-threatening infections in children, elderly, and immune compromised persons. The target of this investigation was to appraise various phenotypic and genotypic characteristics of isolated S. aureus from chicken meat products in Egypt. As well as to evaluate using MALDI-TOF-MS as a prompt, efficient process for detecting S. aureus isolates. On examination of 225 chicken meat samples, identification of staphylococci was 127/225 (56.4%), while 16.8% (38/225) were S. aureus, and 39.5% (89/225) were CNS. S. aureus recovered from 8.3%, 13.3%, 23.3%, 46.6%, 33.3%, and 5% of the examined frozen chickens, chicken fillet, chicken nuggets, chicken shawarma, chicken luncheon, and chicken stock cubes, respectively. Furthermore, additional confirmation using MALDI TOF MS which confirmed all isolates as S. aureus with 100% agreement with the bacteriological examination. Resistance against 13 antibiotics was determined using Kirby-Bauer disc diffusion test, 100%, 78.9%, and 52.6% of the isolates were resistant to penicillin G, tetracycline, and amoxicillin Clavulanic acid, respectively, while 26.3% were resistant to methicillin. On the other hand, the isolates showed high sensitivity to vancomycin, clindamycin, and chloramphenicol with percentages 97.3%, 81.5%, and 68.4% respectively. The resistant strains to methicillin were tested by PCR for the presence of mecA gene, the result was 100% (10/10) positive for mecA gene. The isolates were phenotypically analyzed for their ability of biofilm formation using Tube Method (TM) and Tissue Culture Plate method (TCP). TM divided S. aureus isolates into 4 grades: strong biofilm former, moderate biofilm former, weak biofilm former, and non-biofilm former with percentages18.4%, 15.7%, 13.1%, and 52.6% respectively ,while, TCP revealed 86.8% of S. aureus positive, Fifteen S. aureus were genetically tested for the exitance of icaA and icaD genes which showed 60% and 26.7% were positive for icaD and icaA, respectively, then examined for revelation of enterotoxin genes (sea, seb, sec, sed and see), only seb and sed could be detected with percentage 6.7% and 26.7%, respectively. In conclusion, S. aureus were found in a high percentage in chicken meat products, that showed phenotypic and genotypic virulence factors, in addition to using MALDI TOF as a swift and effectual approach for detecting S. aureus.
Keywords: S. aureus, antibiotic resistant, mecA gene, biofilm formation, enterotoxins, chicken products, MALDI-TOF