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. (c) 2005 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.