Bernardo Katussevani, Pakulat Norbert, Fleer Silke, Schnaith Annabelle, Utermöhlen Olaf, Krut Oleg, Müller Stefan, Krönke Martin
Institute for Medical Microbiology, Immunology, and Hygiene, Medical Center, University of Cologne, Cologne, Germany.
Antimicrob Agents Chemother. 2004 Feb;48(2):546-55. doi: 10.1128/AAC.48.2.546-555.2004.
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.
通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳结合基质辅助激光解吸电离飞行时间质谱和蛋白质免疫印迹分析，研究了抗生素利奈唑胺对金黄色葡萄球菌外毒素分泌的影响。在细菌生长的不同阶段（即540nm处的光密度[OD(540)]为0.05或0.8），用分级亚抑菌浓度的利奈唑胺（MIC的12.5%、25%、50%和90%）处理金黄色葡萄球菌悬液。当在OD(540)为0.05时添加到金黄色葡萄球菌培养物中，利奈唑胺以剂量依赖的方式降低了包括葡萄球菌肠毒素A（SEA）和SEB、双功能自溶素、自溶素、蛋白A以及α和β溶血素在内的特定毒力因子的分泌。相比之下，在90%MIC的利奈唑胺存在下，其他可能无毒的外蛋白在培养上清液中保持不变甚至积累。同样，当在OD(540)为0.8时添加，即在群体感应之后添加，利奈唑胺减少了毒力因子的释放，而发现三酰基甘油脂肪酶、甘油酯水解酶、DnaK或翻译延伸因子EF-Tu等无毒外蛋白的相对丰度增加。一致地，利奈唑胺以剂量依赖的方式降低了金黄色葡萄球菌分泌到培养上清液中的肿瘤坏死因子诱导活性。我们的研究结果表明，金黄色葡萄球菌中毒力因子的表达对利奈唑胺抑制蛋白质合成特别敏感，这在治疗产毒素金黄色葡萄球菌感染中应是一个优势。
