Salicylic acid diminishes Staphylococcus aureus capsular polysaccharide type 5 expression

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Immunology

Background:

• Capsular polysaccharides (CP) of Staphylococcus aureus serotypes 5 and 8 are key virulence factors.
• Salicylic acid (SAL), an aspirin metabolite, is known to influence bacterial virulence factor expression.

Purpose of the Study:

• To investigate the effect of SAL on Staphylococcus aureus capsular polysaccharide production and epithelial cell invasion.
• To elucidate the molecular mechanisms underlying SAL's impact on S. aureus virulence.

Main Methods:

• Exposure of S. aureus strains (Reynolds and Newman) to SAL.
• Assessment of bacterial internalization into MAC-T epithelial cells.
• Analysis of cap5 promoter activity, mgrA and saeRS transcript levels via real-time PCR.
• Quantification of CP5 production.

Main Results:

• SAL pre-exposure significantly increased the internalization of encapsulated S. aureus strains into MAC-T cells.
• SAL treatment decreased cap5 promoter activity and CP5 production in S. aureus Newman.
• SAL exposure led to diminished mgrA transcription and upregulated saeRS transcription.
• Non-encapsulated S. aureus strains showed no significant change in internalization after SAL exposure.

Conclusions:

• Low concentrations of SAL reduce CP production in encapsulated S. aureus, unmasking adhesins and enhancing epithelial cell invasion.
• SAL-induced increased internalization of encapsulated S. aureus may contribute to bacterial persistence in hosts.
• SAL affects global regulators of CP expression (mgrA and saeRS), leading to reduced capsule production.