Influence of clindamycin on the stability of coa and fnbB transcripts and adherence properties of Staphylococcus aureus Newman.

We investigated whether a subinhibitory concentration of clindamycin (Cli), corresponding to 1/2 the strain-specific minimum inhibitory concentration (MIC), could affect expression and stability of transcripts from genes coding for specific adhesins such as fibronectin binding proteins A (fnbA) and B (fnbB) as well as coagulase (coa) in Staphylococcus aureus strain Newman. Furthermore, the effect of 1/2 MIC of Cli on adherence properties and expression of type 5 capsular polysaccharides (CP5) was investigated. Northern slot blot experiments confirmed that the amount of coa- and fnbB-specific mRNA, in contrast to that of fnbA-specific mRNA, was increased 2-fold after treatment of S. aureus Newman with 1/2 MIC of Cli. Analysis of RNA stability revealed that the increased amounts of transcripts of coa and fnbB were due to stabilization of the respective mRNAs. However, when treated with 1/2 MIC of Cli, S. aureus Newman showed no significant changes neither in its adherence patterns to fibrinogen- or fibronectin-coated micotitre plates, nor to epithelial HEp-2 cells and also not in its CP5 expression. Therefore, we conclude that increased mRNA stability of fnbB and coa by 1/2 MIC Cli, in contrast to the situation seen with the protein biosynthesis inhibiting antibiotic florfenicol, does not result in an increase in adherence of S. aureus Newman.