Staphylococcus aureus auxotrophic mutant as new tool of bacterial interference in nasal colonization

BARBAGELATA, MS; ALVAREZ, LP; GORDIOLA, M; CERQUETTI, MC; SORDELLI, DO; BUZZOLA FR

Cordoba

Congreso; 44th Annual Meeting, Argentine Society for Biochemistry and Molecular Biology Research; 2008

S. aureus nasal carriage is a risk factor for infection in humans, particularly in the hospital environment. The active colonization with a strain of S. aureus which possess minimal pathogenic properties is able to prevent colonization by more virulent strains. In this work a murine model of S. aureus nasal colonization was developed. Mice were inoculated by intranasal (ina) via with a suspention of the auxotrophic mutant of S. aureus (NA412, obtained in our lab previously) during three consecutive days. At fourth day, mice were challenged by ina via with one of the representative clinical strains of S. aureus in Argentina [pediatric (HDE288) and cordobes (HU-71) clones]. Bacterial interference was evaluated by colony counting from nasal homogenates at 24 h post-challenge. Viable counts of the clinical strains in the groups of NA412 mice colonized (named G1) decreased significantly when compared with those groups of animals without pre-colonization (named G2) (HU-71 G1: 120 CFU/ml and G2: 9415 CFU/ml, p