Antifungal susceptibility of yeasts isolated from anthropogenic watershed

Abstract Yeasts are unicellular fungi widespread in the environment, and studies suggest that there is a positive correlation between yeast and polluted aquatic environments. The aim of this study was to analyze the diversity and resistance of yeasts isolated from water samples collected along the Arroio Dilúvio in Porto Alegre to antifungals. Yeast isolates from the Arroio Dilúvio were subjected to susceptibility assays against antifungals using the minimum inhibitory concentration (MIC) test, and amplification of the ITS1-5.8S-IT2 region; in addition, the ITS-5.8S region was sequenced for some of the isolates. The amplification product was subjected to PCR-RFLP, and the restriction profile allowed the construction of a dendrogram. Susceptibility tests showed a high prevalence of resistance to azole antifungals, where 16.8% of the isolates had a resistance profile to amphotericin B. The sequence analysis allowed the identification of Candida species, including potentially pathogenic species, and species of the Debaryomyces spp. The resistance to antifungals in yeasts isolated from Arroio Dilúvio reinforces the importance of studies of environmental microbiota, and indicates that environmental degradation influences the phenotype displayed.

摘要 酵母菌是广泛分布于各类环境中的单细胞真菌，已有研究证实酵母菌与受污染的水生环境之间存在正相关关联。本研究旨在分析从巴西阿雷格里港（Porto Alegre）的阿罗约迪卢维奥河（Arroio Dilúvio）沿岸采集的水样中分离得到的酵母菌的多样性及其对抗真菌药物的耐药性。研究采用最低抑菌浓度（minimum inhibitory concentration, MIC）试验，对该河流分离得到的酵母菌开展抗真菌药物敏感性检测，并对ITS1-5.8S-IT2区域进行扩增；此外，还对部分分离株的ITS-5.8S区域进行了测序。将扩增产物进行聚合酶链式反应-限制性片段长度多态性（polymerase chain reaction-restriction fragment length polymorphism, PCR-RFLP）分析，依据限制性酶切图谱构建了系统发育树。敏感性检测结果显示，受试酵母菌对唑类抗真菌药的耐药性检出率较高，其中16.8%的分离株对两性霉素B（amphotericin B）呈现耐药表型。序列分析成功鉴定出假丝酵母属（Candida）物种（含潜在致病物种）以及德巴利酵母属（Debaryomyces spp.）物种。从阿罗约迪卢维奥河分离得到的酵母菌所表现出的抗真菌药物耐药性，进一步凸显了环境微生物群研究的重要价值，同时表明环境退化会影响微生物所呈现的表型特征。