Expression of eap in Staphylococcus aureus is affected by salicylic acid.

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

Estambul

Congreso; XII International Congress of Bacteriology and Applied Microbiology; 2008

IUMS

The ability of S. aureus to adapt to different environments is due to a global regulatory network comprising the loci mgrA and sae amongst others. These regulators are involved in the control of the expression of several virulence factors such as eap, which is a member of the secreted expanded-repertoire adhesive molecule family. Eap is upregulated by sae. Previous studies have also shown that salicylic acid (SAL) can negatively affects the expression of bacterial virulence factors. The aim of this work is to study the effect of SAL on expression of mgrA, sae and eap using reporter plasmids carrying green fluorescent protein (GFP) driven by target gene promoters as well as by quantitative real time PCR (qRTPCR). We demonstrated reduced expression of eap transcript in mgrA mutant through fluorometric assays and RTPCR, suggesting that MgrA is a positive regulator of this adhesin. After seven hours of growth, strains treated with SAL showed reduced expression of mgrA and increased expression of eap without any major effect on sae as compared with non-treated controls in fluorometric assays. The qRTPCR data show that SAL down-regulates mgrA while up regulating sae and eap (mean fold change in gene expression by SAL treatment. mgrA: 0.75 ± 0.09; sae: 1.58 ± 0.19; eap: 2.05 ± 0.59). Altogether, these results show that SAL does affect sae and mgrA, which would alter the expression of several virulence factors driven by these regulators and therefore pathogenesis of S. aureus.