Corynebacterium (C.) diphtheriae is one of the two etiological pathogens for human diphtheria with significant morbidity and mortality. Recently, members of its biovar Belfanti have been described as two novel species, C. belfantii and C. rouxii. The most important virulence factor and also the premise to cause diphtheria is the isolate’s capacity to encode and express the diphtheria toxin (DT). In contrast to C. ulcerans, which represents a potentially zoonotic pathogen, C. diphtheriae (incl. the novel deduced species) has almost exclusively been found to comprise a human pathogen. We here report three rare cases of C. rouxii isolation from dogs suffering from disseminated poly-bacterial exsudative to purulent dermatitis and a traumatic labial defect, respectively. The isolates were identified as C. diphtheriae based on commercial biochemistry and matrix-assisted laser desorption/ionisation–time of flight mass spectrometry (MALDI-TOF MS) analysis. However, recently described specific spectral peaks were highly similar to spectra of C. rouxii, which was confirmed by whole genome sequencing. Further investigations of the dog isolates for the presence of DT by tox gene qPCR revealed negative results. The findings from this study point out that skin infections in companion animals can be colonized by uncommon and so believed human specific pathogens, thereby resembling the clinical signs of cutaneous diphtheria.

白喉棒状杆菌( C. )白喉是人类白喉的两种致病病原体之一，具有显着的发病率和死亡率。最近，其生物群 Belfanti 的成员被描述为两个新物种，C. belfantii和C. rouxii。最重要的毒力因子也是引起白喉的前提是分离株编码和表达白喉毒素（DT）的能力。与代表潜在人畜共患病原体的溃疡梭菌相比，白喉梭菌（包括新推断的物种）几乎完全被发现包含人类病原体。我们在这里报告三例罕见的C. rouxii病例分别从患有播散性多细菌渗出性化脓性皮炎和外伤性唇缺损的狗中分离出来。基于商业生物化学和基质辅助激光解吸/电离-飞行时间质谱（MALDI-TOF MS）分析，分离物被鉴定为白喉杆菌。然而，最近描述的特定光谱峰与C. rouxii的光谱高度相似，这已通过全基因组测序得到证实。进一步调查狗分离株是否存在 DT by tox基因qPCR显示阴性结果。这项研究的结果指出，伴侣动物的皮肤感染可以被不常见的，因此被认为是人类特定的病原体定植，从而类似于皮肤白喉的临床症状。