The ability of Staphylococcus aureus to form biofilms and persisters is a major cause of recalcitrant infections that are difficult to treat. We have examined time-dependent variation in persister population present in stationary-phase planktonic cells and biofilms of S. aureus when treated with bactericidal antibiotics having different cellular targets. Fourteen isolates identified as S. aureus were found to be resistant to three to nine classes of antibiotics tested according to the CLSI guidelines. Among the sensitive isolates, S48 was found to be the strongest biofilm producer, whereas J6 was the weakest. The four antibiotics, ciprofloxacin, daptomycin, tobramycin, and vancomycin, inhibited biofilm formation, whereas daptomycin was the strongest in disrupting 24-hr-old biofilm. Treatment of stationary-phase planktonic cells with 100 × minimum inhibitory concentration (MIC) of these antibiotics showed a typical biphasic pattern indicating the presence of persister cells. Twenty-four-hour-old biofilm of the two isolates tested at 100 × MIC of the antibiotics showed a similar biphasic pattern. Tolerance of biofilm cells was greater as compared with planktonic cells, which could be due to elevated number of persisters found in the biofilm as compared with planktonic cells.

中文翻译：

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金黄色葡萄球菌生物膜和固定相浮游细胞的抗生素耐受性。

金黄色葡萄球菌形成生物膜和持久性的能力是难以治疗的顽固性感染的主要原因。我们已经检查了当用具有不同细胞靶点的杀菌抗生素处理时，存在于固定相浮游细胞和金黄色葡萄球菌生物膜中的持久性种群的时间依赖性变化。鉴定为金黄色葡萄球菌的十四个分离株被发现对根据 CLSI 指南测试的三到九类抗生素具有抗药性。在敏感分离株中，发现 S48 是最强的生物膜生产者，而 J6 是最弱的。环丙沙星、达托霉素、妥布霉素和万古霉素这四种抗生素抑制生物膜形成，而达托霉素破坏 24 小时生物膜的作用最强。用这些抗生素的 100 × 最小抑制浓度 (MIC) 处理静止期浮游细胞显示出典型的双相模式，表明存在持久细胞。在抗生素的 100 × MIC 下测试的两种分离物的 24 小时生物膜显示出类似的双相模式。与浮游细胞相比，生物膜细胞的耐受性更高，