Departament of Parasitology, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
Instituto de Ciências da Saúde - ICS, Universidade Federal da Bahia, Salvador, Brazil.
PLoS Negl Trop Dis. 2018 Sep 17;12(9):e0006766. doi: 10.1371/journal.pntd.0006766. eCollection 2018 Sep.
Ascaris lumbricoides and Necator americanus are soil-transmitted parasites with global geographic distribution, and they represent some of the most common and neglected infections in the world. Periodic treatment with mass drug administration (MDA) in endemic areas is the recommended action put forth by the World Health Organization. However, MDA can cause the selection of subpopulations that possess the genetic ability to overcome the mechanism of drug action. In fact, beta-tubulin gene mutations (codons 167, 198 and 200) are correlated with benzimidazole resistance in nematodes of veterinary importance. It is possible that these SNPs also have strong correlation with treatment resistance in the human geohelminths A. lumbricoides, Trichuris trichiura and hookworms. Here, we aimed to investigate the presence of some of these canonical molecular markers associated with parasite resistance to benzimidazole in N. americanus and A. lumbricoides collected from six Brazilian states. Nested-PCR and PCR-RFLP were used to detect mutations at codons 167 and 198 in 601 individual eggs of A. lumbricoides collected from 62 human stool samples; however, no mutations were found. Codons 198 and 200 were tested in 552 N. americanus eggs collected from 48 patients using the same methodology, which presented a relative frequency of 1.4% and 1.1%, respectively. The presence of these SNPs in N. americanus eggs is an important finding, indicating that with high benzimidazole drug pressure there is potential for benzimidazole resistance to be selected in this hookworm. However, at these low frequencies it does not indicate that there is at present any benzimidazole resistance problem. This is the first systematic study performed in South America, and the study yielded a landscape of the genetic variants in the beta-tubulin gene and anthelmintic resistance to soil-transmitted parasites detected by a simple, rapid and affordable genotyping assay of individual eggs.
美洲钩虫和蛔虫是具有全球地理分布的土壤传播寄生虫，它们是世界上一些最常见和被忽视的感染。世界卫生组织建议在流行地区定期进行大规模药物治疗（MDA）。然而，MDA 可能导致具有克服药物作用机制遗传能力的亚种群选择。事实上，β-微管蛋白基因突变（密码子 167、198 和 200）与兽医重要线虫的苯并咪唑耐药性相关。这些 SNP 与人类土源性蠕虫蛔虫、鞭虫和钩虫的治疗耐药性也可能存在很强的相关性。在这里，我们旨在研究巴西六个州采集的美洲钩虫和蛔虫中一些与苯并咪唑抗性相关的典型分子标记的存在情况。巢式 PCR 和 PCR-RFLP 用于检测从 62 个人类粪便样本中采集的 601 个单个蛔虫卵中的 167 和 198 密码子突变，但未发现突变。使用相同的方法在从 48 名患者中采集的 552 个美洲钩虫卵中检测到 198 和 200 密码子，其相对频率分别为 1.4%和 1.1%。在美洲钩虫卵中存在这些 SNP 是一个重要的发现，表明在高苯并咪唑药物压力下，这种钩虫有可能选择苯并咪唑耐药性。然而，在这些低频率下，这并不表明目前存在任何苯并咪唑耐药问题。这是在南美洲进行的第一项系统研究，该研究展示了β-微管蛋白基因中的遗传变异和通过个体卵简单、快速且经济的基因分型检测到的土壤传播寄生虫对驱虫药的耐药性。
