Pharmacy Practice Division, School of Pharmacy, University of Wisconsin, Madison, Wisconsin, USA.
Antimicrob Agents Chemother. 2012 Jan;56(1):140-7. doi: 10.1128/AAC.05113-11. Epub 2011 Nov 7.
Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strain MW2 harbors a plethora of toxins to mediate its virulence. However, toxin expression and regulation with simulated clinical antimicrobial exposures are unclear. This study evaluated these relationships using an in vitro pharmacodynamic hollow-fiber infection model. Clinical doses of clindamycin, linezolid, minocycline, trimethoprim-sulfamethoxazole (SXT), and vancomycin were simulated over 72 h against MW2 in the hollow fiber model. Expression levels of lukSF-PV and enterotoxin genes sec4, sek, seq, and sel2 were quantified by real-time PCR. Panton-Valentine leukocidin (PVL) was quantified by enzyme-linked immunosorbent assay (ELISA), and cytotoxicity was determined on polymorphonuclear cells (PMNs). Vancomycin produced the maximum MW2 killing (2.53 log(10) CFU/ml) after the first dose, but the greatest sustained killing over 72 h occurred with linezolid and clindamycin. Vancomycin and minocycline induced gene upregulation from 0 to 8 h, followed by downregulation for the remaining simulation period. Clindamycin decreased gene expression in the first 24 h, followed by moderate increases (2.5-fold) thereafter. Linezolid increased gene expression 11.4- to 200.4-fold but inhibited PVL production (0.6 ± 0.3 versus 5.9 ± 0.2 μg/ml, linezolid versus control at 72 h; P < 0.05). Similar effects on PVL production occurred with clindamycin and minocycline. SXT increased PVL production at 48 h (2.8-fold) and 72 h (4.9-fold) of treatment (P < 0.05), resulting in increased PVL cytotoxicity on PMNs. Linezolid, clindamycin, and minocycline were the most effective agents on decreasing the virulence potential in CA-MRSA, notably after 8 h of treatment. SXT had minimal effects on toxin gene regulation, but it increased production and cytotoxicity of PVL toxin in the model and may enhance virulence when it is used to treat severe infections.
社区相关性耐甲氧西林金黄色葡萄球菌（CA-MRSA）株 MW2 携带大量毒素来介导其毒力。然而，在模拟临床抗菌暴露的情况下，毒素的表达和调节尚不清楚。本研究使用体外药效学中空纤维感染模型来评估这些关系。在中空纤维模型中，模拟了临床剂量的克林霉素、利奈唑胺、米诺环素、复方磺胺甲噁唑（SXT）和万古霉素，分别在 72 小时内对 MW2 进行治疗。通过实时 PCR 定量测定 lukSF-PV 和肠毒素基因 sec4、sek、seq 和 sel2 的表达水平。酶联免疫吸附试验（ELISA）定量测定 Panton-Valentine 白细胞毒素（PVL），并在多形核细胞（PMN）上测定细胞毒性。万古霉素在第一次给药后产生最大的 MW2 杀伤（2.53 log(10) CFU/ml），但在 72 小时内，利奈唑胺和克林霉素产生的持续杀伤作用最大。万古霉素和米诺环素在 0 至 8 小时内诱导基因上调，随后在剩余的模拟期间下调。克林霉素在最初的 24 小时内降低了基因表达，然后适度增加（2.5 倍）。利奈唑胺使基因表达增加 11.4-200.4 倍，但抑制了 PVL 的产生（0.6 ± 0.3 与 5.9 ± 0.2 μg/ml，利奈唑胺与对照在 72 小时时相比；P < 0.05）。克林霉素和米诺环素对 PVL 的产生也有类似的影响。SXT 在治疗的 48 小时（2.8 倍）和 72 小时（4.9 倍）时增加了 PVL 的产生（P < 0.05），导致 PMN 上 PVL 毒素的细胞毒性增加。利奈唑胺、克林霉素和米诺环素是降低 CA-MRSA 毒力潜能的最有效药物，特别是在治疗 8 小时后。SXT 对毒素基因调节的影响最小，但它增加了模型中 PVL 毒素的产生和细胞毒性，并且在用于治疗严重感染时可能会增强其毒力。
