Table_1_Identification of Zoophilic Dermatophytes Using MALDI-TOF Mass Spectrometry.pdf

Dermatophytoses represent a major health burden in animals and man. Zoophilic dermatophytes usually show a high specificity to their original animal host but a zoonotic transmission is increasingly recorded. In humans, these infections elicit highly inflammatory skin lesions requiring prolonged therapy even in the immunocompetent patient. The correct identification of the causative agent is often crucial to initiate a targeted and effective therapy. To that end, matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) represents a promising tool. The objective of this study was to evaluate the reliability of species identification of zoophilic dermatophytes using MALDI-TOF MS. The investigation of isolates from veterinary clinical samples suspicious of dermatophytoses suggests a good MALDI-TOF MS based identification of the most common zoophilic dermatophyte Microsporum canis. Trichophyton (T.) spp. usually achieved scores only around the cutoff value for secure species identification because of a small number of reference spectra. Moreover, these results need to be interpreted with caution due to the close taxonomic relationship of dermatophytes being reflected in very similar spectra. In our study, the analysis of 50 clinical samples of hedgehogs revealed no correct identification using the provided databases, nor for zoophilic neither for geophilic causative agents. After DNA sequencing, adaptation of sample processing and an individual extension of the in-house database, acceptable identification scores were achieved (T. erinacei and Arthroderma spp., respectively). A score-oriented distance dendrogram revealed clustering of geophilic isolates of four different species of the genus Arthroderma and underlined the close relationship of the important zoophilic agents T. erinacei, T. verrucosum and T. benhamiae by forming a subclade within a larger cluster including different dermatophytes. Taken together, MALDI-TOF MS proofed suitable for the identification of zoophilic dermatophytes provided fresh cultures are used and the reference library was previously extended with spectra of laboratory-relevant species. Performing independent molecular methods, such as sequencing, is strongly recommended to substantiate the findings from morphologic and MALDI-TOF MS analyses, especially for uncommon causative agents.

皮肤癣菌病（Dermatophytoses）是动物与人类共同面临的重大健康负担。亲动物性皮肤癣菌通常对其原始动物宿主具有高度特异性，但人畜共患传播的案例正日益增多。在人类中，此类感染会引发重度炎症性皮肤损伤，即便免疫功能正常的患者也需要长期治疗。准确鉴定致病菌通常是启动靶向有效治疗的关键。为此，基质辅助激光解吸电离飞行时间质谱（MALDI-TOF MS）是一项极具潜力的技术手段。本研究旨在评估利用MALDI-TOF MS进行亲动物性皮肤癣菌菌种鉴定的可靠性。对疑似皮肤癣菌病的兽医临床样本分离株的分析显示，基于MALDI-TOF MS可对最常见的亲动物性皮肤癣菌犬小孢子菌（Microsporum canis）实现良好的鉴定效果。毛癣菌属（Trichophyton，简称T.）菌株通常仅能达到可靠菌种鉴定的临界得分值，这是因为其参考光谱数量较少。此外，由于皮肤癣菌间紧密的分类学关系会体现在高度相似的光谱中，因此对这些结果需谨慎解读。本研究中，对50份刺猬临床样本的分析显示，无论使用提供的数据库针对亲动物性还是嗜土性致病菌，均未获得正确的鉴定结果。经DNA测序、优化样本处理流程并自主扩展内部参考数据库后，分别获得了针对刺猬毛癣菌（T. erinacei）和节皮菌属（Arthroderma spp.）的可接受鉴定得分。基于得分的距离树状图显示，4种不同节皮菌属嗜土性分离株聚为一类，同时证实了重要亲动物性致病菌刺猬毛癣菌、疣状毛癣菌（T. verrucosum）和班氏毛癣菌（T. benhamiae）之间的紧密亲缘关系——它们在包含多种皮肤癣菌的更大聚类中形成了一个亚分支。综上，若使用新鲜培养物且参考数据库已提前扩展包含实验室相关菌种的光谱，MALDI-TOF MS可适用于亲动物性皮肤癣菌的鉴定。强烈建议辅以独立的分子生物学方法（如测序）来验证形态学及MALDI-TOF MS分析结果，针对罕见致病菌时尤为如此。