Differential gene expression in planktonic and biofilm cells of multiple antibiotic-resistant SalmonellaTyphimurium and Staphylococcus aureus

This study was designed to evaluate gene expression patterns of the planktonic and biofilm cells of Staphylococcus aureus and Salmonella Typhimurium in trypticase soy broth adjusted to pH 5.5 and pH 7.3. The planktonic and biofilm cells of multiple antibiotic-resistant S. aureus (S. aureus(R) ) and S. Typhimurium (S. Typhimurium(R) ) were more resistant to β-lactams than those of antibiotic-susceptible S. aureus (S. aureus(S) ) and S. Typhimurium (S. Typhimurium(S) ) at pH 5.5 and pH 7.3. The relative gene expression levels of norB, norC, and mdeA genes were increased by 7.0-, 4.7-, and 4.6-fold, respectively, in the biofilm cells of S. aureus(S) grown at pH 7.3, while norB, norC, mdeA, sec, seg, sei, sel, sem, sen, and seo genes were stable in the biofilm cells of S. aureus(R) . This study provides useful information for understanding gene expression patterns in the planktonic and biofilm cells of antibiotic-resistance pathogens exposed to acidic stress.