title: Subinhibitory concentrations of linezolid reduce Staphylococcus aureus virulence factor expression.
abstract: The influence of the antibiotic linezolid on the secretion of exotoxins by Staphylococcus aureus was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis combined with matrix-assisted laser desorption ionization-time of flight mass spectrometry and Western blot analysis. S. aureus suspensions were treated with grading subinhibitory concentrations of linezolid (12.5, 25, 50, and 90% of MIC) at different stages of bacterial growth (i.e., an optical density at 540 nm [OD(540)] of 0.05 or 0.8). When added to S. aureus cultures at an OD(540) of 0.05, linezolid reduced in a dose-dependent manner the secretion of specific virulence factors, including staphylococcal enterotoxin A (SEA) and SEB, bifunctional autolysin, autolysin, protein A, and alpha- and beta-hemolysins. In contrast, other presumably nontoxic exoproteins remained unchanged or even accumulated in supernatants in the presence of linezolid at a 90% MIC. Similarly, when added at OD(540) of 0.8, that is, after quorum sensing, linezolid reduced the release of virulence factors, whereas the relative abundance of nontoxic exoproteins such as triacylglycerol lipase, glycerol ester hydrolase, DnaK, or translation elongation factor EF-Tu was found to be increased. Consistently, linezolid reduced in a dose-dependent manner the tumor necrosis factor-inducing activity secreted by S. aureus into the culture supernatants. The results of our study suggest that the expression of virulence factors in S. aureus is especially sensitive to the inhibition of protein synthesis by linezolid, which should be an advantage in the treatment of infections with toxin-producing S. aureus.
authors.affiliation: Institute for Medical Microbiology, Immunology, and Hygiene, Medical Center, University of Cologne, Cologne, Germany.
authors.forename: Katussevani
authors.initials: K
authors.lastname: Bernardo
authors.forename: Norbert
authors.initials: N
authors.lastname: Pakulat
authors.forename: Silke
authors.initials: S
authors.lastname: Fleer
authors.forename: Annabelle
authors.initials: A
authors.lastname: Schnaith
authors.forename: Olaf
authors.initials: O
authors.lastname: Utermöhlen
authors.forename: Oleg
authors.initials: O
authors.lastname: Krut
authors.forename: Stefan
authors.initials: S
authors.lastname: Müller
authors.forename: Martin
authors.initials: M
authors.lastname: Krönke
mesh_terms: D000081:Acetamides / Q000494:pharmacology*; D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics; D015153:Blotting, Western; D002853:Chromatography, Liquid; D030541:Databases, Genetic; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005098:Exotoxins / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D000069349:Linezolid; D013058:Mass Spectrometry; D051379:Mice; D008810:Mice, Inbred C57BL; D008826:Microbial Sensitivity Tests; D023303:Oxazolidinones / Q000494:pharmacology*; D010455:Peptides / Q000737:chemistry; D011492:Protein Hydrolysates / Q000737:chemistry; D040901:Proteomics; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013154:Spleen / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D014357:Trypsin; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D037521:Virulence Factors / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D000081:Acetamides; D000890:Anti-Infective Agents; D001426:Bacterial Proteins; D005098:Exotoxins; D023303:Oxazolidinones; D010455:Peptides; D011492:Protein Hydrolysates; D014409:Tumor Necrosis Factor-alpha; D037521:Virulence Factors; D014357:Trypsin; D000069349:Linezolid