Skin Microbiota in Equine Pastern Dermatitis

Equine pastern dermatitis (EPD), a multifactorial syndrome, manifests as skin lesions of variable severity in the pastern area. Despite the widespread use of antibiotics for treating this condition, the role of bacteria in its pathology is still unclear. The objective was therefore to investigate how EPD itself and antibacterial treatment thereof lead to changes in the bacterial skin microbiota. A case-control study was therefore conducted with 80 client-owned horses that had at least one EPD-affected and one control pastern each. Horses were grouped by the form of EPD, the severity grade and their type of pretreatment. Skin swabs were obtained, and the bacterial diversity was compared between the groups. Bacterial alpha diversity was reduced in affected pasterns (P 0.14). Analyses of beta-diversity confirmed a disordering of the skin microbiota (P = 0.004), that was particularly profound in more severe lesions. The type of pretreatment was not primarily decisive for these perturbations but was likely an enhancing factor. Four differentially abundant families were detected, of which Staphylococcaceae were the most distinct. Their relative abundance was significantly increased in affected pasterns (P = 0.011), particularly in those that had previously received antibacterial treatment. Altogether, our study demonstrates that changes in the microbiota are associated with the form and severity of EPD. A primary and/or secondary role of bacteria as well as the propriety of antibacterial treatment should therefore be further investigated.

马系部皮炎（Equine pastern dermatitis, EPD）是一种多因素综合征，以系部区域出现不同严重程度的皮肤损伤为主要表现。尽管当前临床广泛采用抗生素治疗该病，但细菌在其发病机制中所扮演的角色仍未明确。为此，本研究采用病例对照研究设计，纳入80匹由饲主饲养的马匹，每匹马至少存在1处受EPD累及的系部与1处作为对照的健康系部，并根据EPD的分型、严重程度分级以及研究前预处理类型对马匹进行分组。采集皮肤拭子样本后，对各组间的细菌多样性展开比较分析。结果显示，受累系部的细菌α多样性（alpha diversity）有所降低（P=0.14）；β多样性（beta-diversity）分析证实皮肤菌群存在紊乱（P=0.004），且该紊乱在病变程度更严重的个体中尤为突出。研究前预处理类型并非引发上述菌群紊乱的主要决定性因素，但可能是一类促进因素。本研究共检测到4个丰度存在显著差异的细菌科，其中葡萄球菌科（Staphylococcaceae）的差异最为显著：其在受累系部中的相对丰度显著升高（P=0.011），尤其是此前接受过抗菌治疗的马匹受累系部。综上，本研究证实菌群改变与马系部皮炎（EPD）的分型及严重程度密切相关。因此，细菌在该病中的原发和/或继发作用，以及抗菌治疗的合理性，均有待进一步深入研究。