Griffeth Gregory C, Callori Nancy, Rankin Shelley C, Boston Raymond C, Morris Daniel O
Department of Clinical Studies-Philadelphia, School of Veterinary Medicine, University of Pennsylvania, 3900 Delancey Street, Philadelphia, PA 19104, USA.
Vet Dermatol. 2012 Feb;23(1):57-60, e13. doi: 10.1111/j.1365-3164.2011.01012.x. Epub 2011 Oct 13.
Meticillin-resistant Staphylococcus aureus (MRSA) causes serious skin and soft-tissue infections of humans and animals. Multiple strains of MRSA have been characterized, and one in particular, designated as strain USA 500, causes infections predominantly of horses and the people who work with them. The purpose of this study was to optimize an assay which could subsequently be used to compare the relative avidity of different S. aureus strains for equine corneocytes. Corneocytes were collected from the perineal skin of 10 healthy horses onto adhesive discs. The discs were then incubated at 37°C with an S. aureus field strain at each of three concentrations [10(7), 10(8) and 10(9) colony forming units (CFU)/mL] and for each of three incubation periods (45, 90 and 180 min). After standardized rinsing and staining procedures, discs were examined at ×1,000 magnification and areas containing confluent corneocytes photographed. The percentage of surface area occupied by adherent bacteria was analysed using image processing and analysis software. Significant colour space image processing was required to distinguish bacteria from the ubiquitous melanin granules present within equine corneocytes. Objective and subjective methods were used to determine optimal conditions for specific adherence without introducing confounding factors. A bacterial concentration of 10(8) CFU/mL incubated with corneocytes for 45 min produced maximal bacterial adhesion with the least amount of interbacterial clumping. Future studies should utilize these conditions for optimal assay performance.
耐甲氧西林金黄色葡萄球菌（MRSA）可引起人和动物严重的皮肤及软组织感染。已鉴定出多种MRSA菌株，其中一种特别命名为USA 500菌株，主要引起马以及与马接触的人员感染。本研究的目的是优化一种检测方法，该方法随后可用于比较不同金黄色葡萄球菌菌株对马角质形成细胞的相对亲和力。从10匹健康马的会阴皮肤收集角质形成细胞到粘性圆盘上。然后将圆盘在37°C下与一株金黄色葡萄球菌野外菌株在三种浓度[10(7)、10(8)和10(9)菌落形成单位（CFU）/mL]下分别孵育三个时间段（45、90和180分钟）。经过标准化的冲洗和染色程序后，在1000倍放大倍数下检查圆盘，并拍摄含有融合角质形成细胞的区域。使用图像处理和分析软件分析附着细菌所占的表面积百分比。需要进行显著的颜色空间图像处理，以区分细菌与马角质形成细胞内普遍存在的黑色素颗粒。采用客观和主观方法确定特异性黏附的最佳条件，同时不引入混杂因素。细菌浓度为10(8) CFU/mL与角质形成细胞孵育45分钟时，产生的细菌黏附量最大，且细菌间聚集最少。未来的研究应利用这些条件以实现最佳检测性能。
