Abstract
This descriptive study was done on 100 samples obtained from layer chicken with symptoms of arthritis and decrease egg production in Assuit Governorate Egypt. A total of 37 Staphylococcal isolates were recovered, of which 21(56.7%) identified as coagulase positive Staphylococcus aureus (SA) and 16 (43.2%) were identified as coagulase negative staphylococci (CoNS). Sensitivity test of S. aureus isolates was performed against 10 common used chemotherapeutic agents, the results showed that all tested isolates were resistant to Amoxicillin , cefoxitin, and methicillin, while all were sensitive to vancomycin and Tylosin. For phenotypic analysis of biofilm formation, Congo Red Agar (CRA) test of 21 coagulase positive S. aureus isolates revealed that 76.2 % of these isolates were positive for biofilm production with variay degrees. A total of 12 representative coagulase positive staphylococci isolates were screened by multiplex PCR targeted the 16S rRNA, nuc and mecA genes to discriminate strains and to detect methicillin resistant strains(MRSA) , another PCR assay for presence of biofilm related genes, icaA, icaD, and PCR assay to detect prevalence of enterotoxin genes (SEs) . The 12 isolates were confirmed as S. aureus .Among the 12 S. aureus strains, 11 were found carrying mecA gene and only one isolate was mecA negative, biofilm related genes were icaD gene detected in 8 of11 S.aureus strains(72.7%), while icaA gene was found in one strain only(9%)and one strain was positive for both icaA and icaD genes. All the examined 11 mecA positive S.aureus strains harbourd enterotoxins genes distributed as follow:
Sea found in (81.8%), seb (9%) and seb, sec in (9%) .Our results indicated that poultry S. aureus isolates are likely to be enterotoxigenic and biofilm producing ,and this may constitute a risk for poultry and might pose a public health hazard.

Key words: Methicillin–Resistant Staphylococcus aureus (MRSA), Enterotoxins, layer chicken, Biofilm , PCR