Abstract
The dramatic increase in the prevalence of antimicrobial-resistant Staphylococcus aureus (S. aureus) is receiving wide spread attention, due to multi-resistant strains, diminishing the usefulness of antibiotics in human and animal medicine and, thereby limiting therapeutic options. In this study, 250 samples of chicken swabs were collected from five different poultry farms (50 samples from each farm) within Upper Egypt area. 157 staphylococci strains were detected with an isolation rate of (62.8%). isolates of S. aureus were confirmed using standard microbiological methods. Eighty one (55.9%) were coagulase positive staphylococci, and 76(48.4%) were coagulase negative staphylococci, phenotypic prediction of β-lactam resistance among the 81 isolated coagulase positive staphylococci was declared using disk diffusion test against, cefoxitin and oxicillin which were used for detection of mecA mediated β-lactam resistance (methicillin resistance) while penicillin and amoxicillin/clavulinic acid (AMC) antibiotic discs were used to monitor blaZ mediated resistance. Out of 81 isolates ,all isolates were 100% resist to oxacillin and 93.8 % were resist to cefoxitin, while 90.1 % were resist to penicillin and 87.6% were resist to AMC. The antibiotic susceptibility results were judged by PCR, the mecA ,and blaZ genes were tested for the evaluation of the susceptibility of coagulase positive Staphylococci against oxacillin and ß-lactams, the thirty one reprsentative coagulase positive staphylococci isolates confirmed that all the isolates were Staphylococci by successful amplification of the 228 bp PCR product of the Staphylococcal specific 16S rRNA gene. While , 20 isolates were confirmed to be S.aureus by successful amplification of 279 bp PCR product of the S.aureus specific thermonuclease gene .On using the same multiplex PCR assay, detection of blaZ and/or mecA genes were performed through successful amplification of 517 bp and /or 147 bp specific products, respectively. Out of the 31 reprsentative coagulase positive Staphylococci isolated from broiler chickens, 20 (64.5%) were mecA gene positive while 23 (74%) were β- blaZ gene positive. Also, 15 (48.3%) of the isolates carried both mecA and blaZ genes while only 3 isolates (9.6%) were negative for both genes. Concerning MIC of 12 representative coagulase positive staphylococci isolates against 12 selected antibiotics commonly used in poultry farms, 100% of isolates were resistant to streptomycin, spectinomycin ,ampicillin, Cefotax, Trimethoprim-sulphamethazole, gentamycin, and Methicillin with MIC >128, while 100% of isolates were sensitive to tylosin, lincomycine, enrofloxacin, ciprofloxacin and oxytetracyclin.

Key words: Staphylococcus aureus, broiler chickens, PCR , mecA, blaZ genes