Abstract
In this study, a total of 147 random samples from chicken meat, chicken liver, minced chicken meat and chicken luncheon samples were collected from different markets. Staphylococcus aureus was isolated from these products at a percentage of 11.4 % , 9%, 16.2% and 26.1 % respectively.
The sensitivity of Staph. aureus isolates to antimicrobial agents indicated that the isolates were sensitive to amikacin followed by gentamycin and amoxicillin with a percentage of 52 %, 48% and 30%, respectively. On the other hand, 100% of isolates were resistant to methicillin followed by penicillin, doxycycline, Ampicillin, ciprofloxacin, and sulpha-methoxazole with a percentage of 96.3%, 96.3%, 93%, 89%, and 81%, respectively.
The multidrug resistance (MAR) index values were ranged between 0.33 and 1. All the isolates showed resistance to at least 3 out 9 antibacterial agents tested. Six Staph. aureus isolates were selected (4 resistant to penicillin and 2 sensitive to penicillin) and screened for plasmid. The results revealed that the 4 resistant isolates were harbored plasmid with molecular size ranging from 18 and 22kbp. The 4 resistant isolates were divided to 2 groups (the first group was subcultured 5 times with sublethal dose of penicillin and the second group was subcultured 5 times in the absence of penicillin) and screened for plasmid. It was found that the 2 isolates which subjected to 5 times repeated subculture with sublethal dose of penicillin maintained their plasmids, while the 2 isolates which subjected to 5 times repeated subculture in the absence of penicillin lost their plasmids.

PCR technique was used as confirmatory tool for detection of mecA gene. Eight isolates of Staph .aureus were randomly selected for detection of mecA gene using specific primers. Five out of eight (62.5 %) isolates were positive for mecA gene.

Key words: S.aureus , antibiotic resistance ,PCR mec gene ,chicken