Staphylococcus aureus agr genotypes with enterotoxin production capabilities can resist neutrophil bactericidal activity

Staphylococcus aureus pathogenicity is mainly due to the production of a nu mber of secreted and cell surface-associated proteins under the regulation of the agr gene. A region of the agr gene was used to subgroup S. aureus st rains according to restriction fragment length polymorphisms. Additionally, strains were subtyped according to the coagulase gene in order to strength en discriminatory power. Virulence capabilities of agr genotype subgroups w ere evaluated using an in vitro neutrophil bactericidal assay, which showed that prevalent genotypes were significantly better at evading this primary host defense. Multiplex PCR was then used to detect enterotoxin genes amon g the genotype subgroups in order to determine possible virulence candidate s that enable strains to combat neutrophil killing. The prevalent genotype strains were found to possess higher production capabilities for enterotoxi n A than did low-prevalence strains. The significance of enterotoxin A prod uction capabilities in affecting pathogenicity of S. aureus st:rains was ev aluated and found to have a profound effect on neutrophil killing abilities . The use of a large epidemiological database as a tool for subgrouping str ains with varying degrees of pathogenicity has allowed the identification o f relevant and previously undefined virulence factors that affect a pathoge n's capability to overcome host immune defenses.