Department of Medicine, the University of Toronto, Toronto, Ontario, Canada.
Mycology Section, Mediprobe Research Inc., London, Ontario, Canada.
PLoS One. 2020 Sep 29;15(9):e0239648. doi: 10.1371/journal.pone.0239648. eCollection 2020.
Onychomycosis is estimated at a prevalence of 10% worldwide with the infecting organism most commonly Trichophyton rubrum (T. rubrum). Traditional culture identification of causative organisms has inherent risks of overestimating dermatophytes, like T. rubrum, by inhibiting the growth of possible nondermatophyte mould (NDM) environmental contaminants which could be causative agents. Recently, molecular methods have revealed that a proportion of onychomycosis cases in North America may be caused by mixed infections of T. rubrum as an agent co-infecting with one or more NDM. Determining the global burden of mixed infections is a necessary step to evaluating the best therapies for this difficult-to-treat disease. To determine the prevalence of mixed infections in a global population, nail samples from onychomycosis patients in Brazil, Canada, and Israel (n = 216) were analyzed by molecular methods for the presence of dermatophytes and five NDMs. If an NDM was detected, repeat sampling was performed to confirm the NDM. T. rubrum was detected in 98% (211/216) of infections with 39% mixed (84/216). The infection type was more likely to be mixed in samples from Brazil, but more likely to be a dermatophyte in samples from Canada and Israel (Χ2 = 16.92, df = 2, P<0.001). The most common cause of onychomycosis was T. rubrum. In all countries (Brazil, Canada and Israel combined) the prevalence of dermatophyte (Χ2 = 211.15, df = 3, P<0.001) and mixed (dermatophyte and NDM; Χ2 = 166.38, df = 3, P<0.001) infection increased with patient age. Our data suggest that mixed infection onychomycosis is more prevalent than previously reported with the aging population being at increased risk for mixed infections.
甲真菌病的全球患病率估计为 10%，最常见的致病微生物为红色毛癣菌（T. rubrum）。传统的致病微生物培养鉴定方法存在固有风险，可能会高估红色毛癣菌等皮肤癣菌，因为它会抑制可能为非皮肤癣菌的环境污染物（NDM）的生长，而这些污染物可能是致病因素。最近，分子方法显示，北美洲部分甲真菌病病例可能是由红色毛癣菌与一种或多种 NDM 混合感染引起的。确定混合感染的全球负担是评估这种难治性疾病最佳治疗方法的必要步骤。为了确定全球人群中混合感染的流行率，对来自巴西、加拿大和以色列的甲真菌病患者（n=216）的指甲样本进行了分子方法分析，以确定是否存在皮肤癣菌和五种 NDM。如果检测到 NDM，则进行重复采样以确认 NDM。98%（211/216）的感染中检测到红色毛癣菌，其中 39%（84/216）为混合感染。巴西样本中感染类型更可能为混合感染，但加拿大和以色列样本中更可能为皮肤癣菌感染（Χ2=16.92，df=2，P<0.001）。最常见的甲真菌病病因是红色毛癣菌。在所有国家（巴西、加拿大和以色列），皮肤癣菌（Χ2=211.15，df=3，P<0.001）和混合感染（皮肤癣菌和 NDM；Χ2=166.38，df=3，P<0.001）的患病率均随患者年龄的增长而增加。我们的数据表明，混合感染性甲真菌病的患病率高于以往报道，老年人群面临更高的混合感染风险。
