Phenotypic and molecular characterization of Staphylococcus aureus strains of veterinary, dairy and human origin.

Austrian veterinary (n=91), dairy (n=86), and human strains (n=48) of Staphylococcus aureus were tested for various phenotypic properties including clumping factor, egg-yolk reaction, production of thermonuclease and susceptibility to 14 antibiotics. In addition the expression of enterotoxins (A-E), and the presence of enterotoxin genes sea to sej and tst was determined. Significant differences in antimicrobial susceptibility were found with 84.6% of veterinary, 57.0% of dairy, and 20.8% of human strains susceptible to all antibiotics tested (P<0.0005). More human strains produced enterotoxins (41.7%) than veterinary (9.9%) and dairy strains (12.6%) while 40.7% and 38.5% of veterinary, 47.7% and 52.3% of dairy, and 77.1% and 87.5% of human strains were se- and tst-positive, respectively. AFLP analysis revealed nine clusters with over- or under-representation of strains with specific characteristics. Strains clustered according to origin (veterinary, dairy, and human) and/or presence of toxin genes and antimicrobial resistance.