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.

中文翻译：

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在大鼠伤口感染模型中，潜在的因素导致SAAP-148的抗菌效果不佳。

背景技术我们研究了合成的抗菌肽SAAP-148的功效，该肽对带状小鼠皮肤上的耐甲氧西林金黄色葡萄球菌（MRSA）有效。出乎意料的是，在我们的实验研究中，使用切除伤口的大鼠，SAAP-148对MRSA无效。因此，我们调查了可能导致SAAP-148疗效差的因素。随后，我们在适应性大鼠研究中优化了方案并评估了SAAP-148的功效。方法我们将100 µL SAAP-148与1 cm2的伤口敷料一起温育1 h，并确定未吸收的肽溶液量。此外，在50％（v / v）人血浆，焦油或皮肤提取物或PBS中，将105个菌落形成单位（CFU）/ mL MRSA暴露于递增剂量的SAAP-148。孵育30分钟后，确定了活细菌的数量。接下来，将离体皮肤模型接种MRSA 1小时，然后暴露于SAAP-148。最后，将大鼠背部的切除伤口接种107 CFU MRSA过夜，并用SAAP-148处理4 h或24 h。随后，确定活细菌的数目。结果与Cuticell，Parafilm和Tegaderm膜相反，在用纱布，Mepilex边界和Oppost Post-op孵育后，回收了不到20％的肽溶液。此外，在血浆中，焦油或皮肤提取物的SAAP-148剂量要比PBS中的SAAP-148降低2对数，以达到MRSA的2对数减少（LR）。将离体模型暴露于SAAP-148 24小时会导致LR比1小时或4小时暴露时间低4倍。此外，SAAP-148导致1。与105 CFU MRSA相比，在107 CFU的负载下平均LR低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。最终，在一项改编的大鼠研究中，SAAP-148未能减少细菌数量。结论伤口敷料对SAAP-148的吸收，伤口渗出液中的成分，在SAAP-148暴露期间再次定殖以及高细菌载量等因素可能导致SAAP-148对MRSA的抗微生物作用较弱。大鼠模型。