Background Intercellular adhesion and biofilm production by Staphylococcus aureus makes these bacteria resistant to antimicrobial therapy. Here, Methicillin-resistant Staphylococcus aureus (MRSA) strains were characterized and the prevalence of genes encoding adhesion factors and biofilm formation was determined. Results All 248 MRSA isolates identified by cefoxitin disc diffusion were positive for the mec A gene. SCC mec -IV was the most frequently detected genotype (92.7%) and SCC mec -IVa was also very prevalent (84.3%). The quantitative microtiter plate assay showed that all the isolates were able to produce biofilm with levels ranging from high (21%) to moderate (46.4%) to low (32.7%). All the strains possessed the icaD/icaA genes and produced biofilm ( P < 0.05). None of the isolates possessed the bap gene . Furthermore, 94.8% of the isolates were positive for eno, 80.2% for clfA and for clfB , 78.2% for fnbA , 76.2% for ebps , 62.2% for fib , 39.9% for cna and 29.0% for fnbB. Also, nearly 69.8% of the isolates were positive for the gene sarA . All four agr groups were present: agr group 1 was predominant with 39.5%; agr group 3. agr group 2 and 3 strains carried more toxin-producing genes, and frequently produced more toxin. Sixty-six (26.6%) of the strains were multidrug resistant. All were vancomycin sensitive. Agr group I is more resistant to ciprofloxacin and gentamicin while agr group III is more resistant to erythromycin. Maximum sensitivity was to gentamicin and SXT, and they could be considered drugs of choice for controlling MRSA mediated infections in this region. Conclusions Biofilm development in MRSA might be an ica dependent and one needs to investigate the involvement of other global regulators, agr and sarA , and their contribution to the biofilm phenotype, as the high rate of biofilm production among the studied strains of S. aureus .

The genes of Staphylococcus aureus encode several toxins causing or strongly suspected of causing specific diseases and adverse symptoms. The distribution of genes encoding superantigens and the gene profiles and genetic background of Palestinian strains of methicillin-resistant Staphylococcus aureus (MRSA) were determined. Strains separated into 12 clonal complexes (CCs) and 41 spa types, and possessed at least one of the studied enterotoxin genes: seo being most prevalent in 69.7% of the strains: followed by seh in 53.3% of the strains. Many (42.6%) of the strains possessed the genes for the classic staphylococcal enterotoxin (SE) sea, seb, sec, sed, and see, whereas 69.2% of the strains possessed the genes of the enterotoxin gene cluster, (egc), seg, seo, seh, sei, sem, seq, sej, sen, sek, sep, seu, sel, ser. Of the strains of S. aureus possessing the genes for Panton-Valentine leucocidin (PVL, n=105) among the strains of CA-MRSA, 16.2% (17/105) belonged to CC8-t008 and 18.1% (19/105) to CC80-t044. All four accessory gene regulator (agr) groups were present with agr group 1 being predominant in 44.1% of the strains. Forty-nine (25%) strains were multidrug resistant (MDR). This study provides information on the molecular markers of strains of S. aureus in clinical samples taken from Palestinian patients, including the characteristics of toxin genes possessed by Palestinian strains of CA-MRSA.