Sanchez Carlos J, Shiels Stefanie M, Tennent David J, Hardy Sharanda K, Murray Clinton K, Wenke Joseph C
Extremity Trauma & Regenerative Medicine Task Area, US Army Institute of Surgical Research, 3698 Chambers Pass, JBSA, Fort Sam Houston, TX, 78234, USA.
Clin Orthop Relat Res. 2015 Sep;473(9):2874-84. doi: 10.1007/s11999-015-4300-3.
Local antimicrobial delivery through polymethylmethacrylate beads (PMMA), commonly vancomycin, is used for the treatment of contaminated open fractures but has limited activity against Staphylococcus aureus biofilms, which occur commonly in such fractures. Rifamycins have activity against biofilms and are an effective treatment for osteoarticular infections involving staphylococcal biofilms, but there are limited studies evaluating the activity of rifamycin derivatives, other than rifampin, against biofilms of S. aureus and evaluating incorporation of these drugs into PMMA for treatment of contaminated open fractures.
QUESTIONS/PURPOSES: (1) Are rifamycin derivatives effective against established biofilms of clinical isolates of S. aureus? (2) Can PMMA be used as a carrier for rifamycin derivatives?
Biofilms were developed and evaluated for susceptibility to a panel of antimicrobials in vitro using the minimum biofilm eradication concentration high-throughput model. Susceptibility was assessed by measuring bacterial recovery at 6 and 24 hours after antimicrobial treatment. Activity of rifamycin derivatives against intracellular bacteria was also evaluated using a gentamicin protection assay. Evaluation of PMMA as a carrier for rifampin and rifamycin derivatives was determined by assessing the curing time subsequent to loading of rifamycins and characterizing the release kinetics of rifamycins at daily intervals for 14 days from PMMA by performing bioassays.
Rifamycin derivatives between 1 and 8 µg/mL reduced bacteria within biofilms 5- to 9-logs and prevented bacterial recovery up to 24 hours post-treatment, indicating near to complete eradication of biofilms. Rifamycin derivatives at 32 µg/mL had activity against intracellular staphylococci, significantly reducing the number of internalized bacteria with limited effects on osteoblast viability. Rifampin was the only rifamycin observed to have a suitable release profile from PMMA, releasing 49% of the total antibiotic and maintaining a sustained released profile up to 14 days at a mean 28 ± 6 μg/mL.
Rifampin can be incorporated into PMMA and eluted at concentrations effective against biofilms and intracellular staphylococci.
Our in vitro findings suggest that local delivery of rifampin may be an effective strategy for the prevention and/or treatment of open fractures where S. aureus biofilms might develop. Clinical studies are needed to characterize what role this approach might have in the prevention and treatment of infections involving biofilms.
通过聚甲基丙烯酸甲酯珠（PMMA）进行局部抗菌药物递送，通常使用万古霉素，用于治疗污染的开放性骨折，但对金黄色葡萄球菌生物膜的活性有限，而这种生物膜在这类骨折中很常见。利福霉素对生物膜有活性，是治疗涉及葡萄球菌生物膜的骨关节炎感染的有效方法，但除利福平外，评估利福霉素衍生物对金黄色葡萄球菌生物膜的活性以及评估这些药物掺入PMMA用于治疗污染开放性骨折的研究有限。
问题/目的：（1）利福霉素衍生物对金黄色葡萄球菌临床分离株形成的成熟生物膜是否有效？（2）PMMA能否用作利福霉素衍生物的载体？
使用最小生物膜根除浓度高通量模型在体外培养生物膜并评估其对一组抗菌药物的敏感性。通过测量抗菌治疗后6小时和24小时的细菌回收率来评估敏感性。还使用庆大霉素保护试验评估利福霉素衍生物对细胞内细菌的活性。通过评估加载利福霉素后的固化时间并通过生物测定法每隔一天表征利福霉素从PMMA中14天的释放动力学，来确定PMMA作为利福平和利福霉素衍生物载体的评估。
1至8μg/mL的利福霉素衍生物使生物膜内的细菌减少5至9个对数，并在治疗后24小时内阻止细菌恢复，表明生物膜几乎完全被根除。32μg/mL的利福霉素衍生物对细胞内葡萄球菌有活性，显著减少内化细菌的数量，对成骨细胞活力的影响有限。利福平是唯一观察到从PMMA具有合适释放曲线的利福霉素，释放了49%的总抗生素，并在平均28±6μg/mL的水平上维持持续释放曲线长达14天。
利福平可以掺入PMMA中，并以有效对抗生物膜和细胞内葡萄球菌的浓度洗脱。
我们的体外研究结果表明，局部递送利福平可能是预防和/或治疗可能形成金黄色葡萄球菌生物膜的开放性骨折的有效策略。需要进行临床研究来确定这种方法在预防和治疗涉及生物膜的感染中可能发挥的作用。
