背景:我们研究了合成抗菌肽SAAP-148的功效,该肽在胶带剥离的小鼠皮肤上对耐甲氧西林金黄色葡萄球菌(MRSA)有效。出乎意料的是,在我们使用具有切除伤口的大鼠的初步研究中,SAAP-148对MRSA无效。因此,我们调查了可能导致SAAP-148疗效不佳的因素.随后,我们优化了方案,并在一项适应性大鼠研究中评估了SAAP-148的疗效.
方法:我们将100μLSAAP-148与1cm2伤口敷料孵育1小时,并确定肽溶液的未吸收体积。此外,将105个菌落形成单位(CFU)/mLMRSA暴露于50%(v/v)人血浆中增加剂量的SAAP-148,eschar或皮肤提取物或PBS。孵育30分钟后,确定了活细菌的数量。接下来,体外皮肤模型用MRSA接种1小时并暴露于SAAP-148。最后,用107CFUMRSA接种大鼠背部的切除伤口过夜,并用SAAP-148处理4小时或24小时。随后,确定了活细菌的数量。
结果:与Cuticell相反,Parafilm和Tegaderm胶片,用纱布孵育后回收<20%的肽溶液,Mepilex边界和OpsitePost-op。此外,在等离子体中,与PBS中的SAAP-148相比,需要>20倍更高的SAAP-148剂量以实现MRSA的2-log减少(LR)。离体模型暴露于SAAP-14824小时导致LR比1小时或4小时暴露期低4倍。此外,SAAP-148在107CFU的负荷下导致平均LR比105CFUMRSA低1.3倍。此外,将离体切除伤口模型暴露于SAAP-148导致LR比胶带剥离的皮肤低1.5倍。最后,SAAP-148在适应性大鼠研究中未能减少细菌计数。
结论:几个因素,如伤口敷料对SAAP-148的吸收,伤口渗出物中的成分,SAAP-148暴露期间的重新定殖和高细菌负荷可能导致SAAP-148对大鼠模型中MRSA的抗微生物效果差。
BACKGROUND: We investigated the efficacy of a synthetic antimicrobial peptide SAAP-148, which was shown to be effective against Methicillin-resistant Staphylococcus aureus (MRSA) on tape-stripped mice skin. Unexpectedly, SAAP-148 was not effective against MRSA in our pilot study using rats with excision wounds. Therefore, we investigated factors that might have contributed to the poor efficacy of SAAP-148. Subsequently, we optimised the protocol and assessed the efficacy of SAAP-148 in an adapted rat study.
METHODS: We incubated 100 µL of SAAP-148 with 1 cm2 of a wound dressing for 1 h and determined the unabsorbed volume of peptide solution. Furthermore, 105 colony forming units (CFU)/mL MRSA were exposed to increasing dosages of SAAP-148 in 50% (v/v) human plasma, eschar- or skin extract or PBS. After 30 min incubation, the number of viable bacteria was determined. Next, ex vivo skin models were inoculated with MRSA for 1 h and exposed to SAAP-148. Finally, excision wounds on the back of rats were inoculated with 107 CFU MRSA overnight and treated with SAAP-148 for 4 h or 24 h. Subsequently, the number of viable bacteria was determined.
RESULTS: Contrary to Cuticell, Parafilm and Tegaderm film, < 20% of peptide solution was recovered after incubation with gauze, Mepilex border and Opsite Post-op. Furthermore, in plasma, eschar- or skin extract > 20-fold higher dosages of SAAP-148 were required to achieve a 2-log reduction (LR) of MRSA versus SAAP-148 in PBS. Exposure of ex vivo models to SAAP-148 for 24 h resulted in a 4-fold lower LR than a 1 h or 4 h exposure period. Additionally, SAAP-148 caused a 1.3-fold lower mean LR at a load of 107 CFU compared to 105 CFU MRSA. Moreover, exposure of ex vivo excision wound models to SAAP-148 resulted in a 1.5-fold lower LR than for tape-stripped skin. Finally, SAAP-148 failed to reduce the bacterial counts in an adapted rat study.
CONCLUSIONS: Several factors, such as absorption of SAAP-148 by wound dressings, components within wound exudates, re-colonisation during the exposure of SAAP-148, and a high bacterial load may contribute to the poor antimicrobial effect of SAAP-148 against MRSA in the rat model.