Student Research Committee Center, Mazandaran University of Medical Sciences, Sari, Iran; Department of Medical Mycology and Parasitology, School of Medicine, Mazandaran University of Medical Sciences, Sari, Iran.
Department of Medical Parasitology and Mycology, Faculty of Medicine, Urmia University of Medical Sciences, Urmia, Iran; Cellular and Molecular Research Center, Urmia University of Medical Sciences, Urmia, Iran.
J Mycol Med. 2018 Mar;28(1):59-64. doi: 10.1016/j.mycmed.2017.12.007. Epub 2018 Feb 27.
Tricyclazole as a common fungicide wildly used to control rice blast disease in the Asian country may induce azole resistance in Aspergillus fumigatus isolates. The main reason of the acquired azole resistance is probably environmental exposure through wide fungicide use in agriculture. The present study was conducted with the aim of investigating the current status of the azole-resistant A. fumigatus obtained from the paddy fields with exposure to tricyclazole. A total of 108 soil samples were collected from four different locations of paddy fields in Mazandaran Province, Iran. Pure fungal colonies were initially identified based on the conventional tools, and then reconfirmed by using DNA sequencing of the partial ß-tubulin gene. In addition, the in vitro antifungal susceptibility was determined using the Clinical and Laboratory Standards Institute document (CLSI) M38-A2. The identification of the mutations in the CYP51A gene was accomplished by the implementation of the polymerase chain reaction amplification assay on the selected isolates. Overall, 31 of 108 (28.7%) isolates were identified as A. fumigatus, four (3.7%) of which were recognized as azole-resistant with MICs of itraconazole ≥8μg/ml and voriconazole ≥4μg/ml. Only two out of the four azole-resistant A. fumigatus isolates harboured TR34/L98H variant and the other two isolates were identified as azole-resistant without any CYP51A gene mutations. However, other point mutations (TR46/Y121F/T289A) were not detected in the CYP51A gene. The high molecular structure similarity between environmental and medical triazoles may result in the selection of resistance mechanisms. Nonetheless, one might conclude that tricyclazole with different molecular structures against medical azoles induces azole-resistance in A. fumigatus isolates. The behavior of such pesticides as tricyclazole in the rice paddy fields would have an effective role in the development of azole-resistance that requires detailed information.
三环唑作为一种在亚洲国家广泛用于防治稻瘟病的常用杀菌剂，可能会导致烟曲霉分离株对唑类药物产生耐药性。获得唑类耐药性的主要原因可能是由于农业中广泛使用杀菌剂而导致的环境暴露。本研究旨在调查接触三环唑的稻田中获得的唑类耐药烟曲霉的现状。从伊朗马赞达兰省四个不同稻田地点共采集了 108 个土壤样本。最初根据常规工具初步鉴定了纯真菌菌落，然后通过β-微管蛋白基因部分序列的 DNA 测序进一步确认。此外，还使用临床和实验室标准协会文件（CLSI）M38-A2 测定了体外抗真菌药敏性。通过对选定分离株实施聚合酶链反应扩增试验，完成了 CYP51A 基因中突变的鉴定。总的来说，在 108 个分离株中，有 31 个（28.7%）被鉴定为烟曲霉，其中 4 个（3.7%）被鉴定为唑类耐药，其伊曲康唑 MIC≥8μg/ml，伏立康唑 MIC≥4μg/ml。在这 4 株唑类耐药烟曲霉分离株中，只有 2 株携带 TR34/L98H 变异，而另外 2 株则被鉴定为唑类耐药，而 CYP51A 基因没有任何突变。然而，在 CYP51A 基因中未检测到其他点突变（TR46/Y121F/T289A）。环境和医学三唑类化合物的高分子结构相似可能导致耐药机制的选择。尽管如此，人们可以得出结论，三环唑具有与医学唑类药物不同的分子结构，会导致烟曲霉分离株对唑类药物产生耐药性。三环唑等杀虫剂在稻田中的行为会对唑类耐药性的发展产生有效作用，需要详细信息。
