Salicylic acid diminishes Staphylococcus aureus capsular polysaccharide type 5 expression.

ALVAREZ LP; BARBAGELATA MS; CHEUNG, AL; SORDELLI DO; BUZZOLA FR

INFECTION AND IMMUNITY

ASM Press

Lugar: Washington DC; Año: 2010 vol. 78 p. 1339 - 1344

0019-9567

Capsular polysaccharide (CP) serotypes 5 (CP5) and 8 (CP8) are major S. aureus virulence factors. Previous studies have shown that salicylic acid (SAL), the main aspirin metabolite, affects the expression of certain bacterial virulence factors. In the present study, we have found that S. aureus strain Reynolds (CP5) cultured with SAL was internalized by MAC-T cells in higher numbers than strain Reynolds organisms not exposed to SAL. Furthermore, the internalization of the isogenic non-encapsulated Reynolds strain into MAC-T cells was not significantly affected by pre-exposure to SAL. Pretreatment of S. aureus strain Newman with SAL also enhanced internalization into MAC-T cells compared with untreated controls. We evaluated in strain Newman organisms the activity of the major cap5 promoter, which was significantly decreased upon pre-exposure to SAL. Diminished transcription of mgrA and up-regulation of the saeRS transcript, both global regulators of CP expression, was found in S. aureus cultured in the presence of SAL, as ascertained by real time PCR analysis.  In addition, CP5 production by S. aureus Newman was also decreased by treatment with SAL.  Collectively, our data demonstrate that exposure of encapsulated S. aureus strains to low concentrations of SAL reduced CP production, thus unmasking surface adhesins and leading to an increased capacity of staphylococci to invade epithelial cells.  The high capacity of internalization of the encapsulated S. aureus strains by SAL pretreatment may contribute to the persistence of the bacteria in certain hosts.