Aromatic Compound-DependentStaphylococcus aureusIs Safe in a Nasal Colonization Leukopenic Murine Model

Staphylococcus aureus nasal carriage is a risk factor for individuals suffering from trauma, surgical procedures, invasive devices, and/or decreased immunity. Recently, we demonstrated that artificial nasal colonization with an attenuated S. aureus mutant reduced by bacterial interference with the colonization of pathogenic strains of S. aureus . This could be an optional tool to diminish the rate of S. aureus infections in hospitalized patients. The aim of this study was to construct a safe Δ aroA mutant of S. aureus and to discriminate it from nasal colonizing and osteomyelitis S. aureus isolates by Sma I pulsed-field gel electrophoresis (PFGE) typing. The Δ aroA mutant, named RD17, exhibited an LD 50 (3.2 × 10 6 colony-forming unit (CFU)) significantly higher than that of the parental strain (2.2 × 10 3  CFU). The colony number of the RD17 mutants recovered from nares of leukopenic mice was similar to that observed in the animals of the control group. Therefore, the Δ aroA mutant was demonstrated to be safe due to maintaining low growth levels in the nares regardless of immune status of the animals. PFGE typing allowed the unequivocal identification of the S. aureus and differentiation of aroA mutants in nasal colonizing and osteomyelitis isolates. This information could be important to discriminate endogenous infections from laboratory strains of S. aureus .