Multilocus sequence analysis of Echinococcus granulosus strains isolated from humans and animals in Iran

Echinococcus granulosus is now considered a complex consisting of at least four species and ten genotypes. Different molecular targets have been described for molecular characterization of E. granulosus; however, in almost all studies only one or two of the targets have been used, and only limited data is available on the utilization of multiple loci. Therefore, we investigated the genetic diversity among 64 strains isolated from 138 cyst specimens of human and animal isolates, using a set of nuclear and mitochondrial genes; i.e., cytochrome c oxidase subunit 1 (cox1), NADH dehydrogenase subunit 1 (nad1), ATPase subunit 6 (atp6), 12S rRNA (12S), and Actin II (act II). In comparison to the use of molecular reference targets (nad1 + cox1), using singular target (act II or 12S or atp6) yielded lower discriminatory power. Act II and 12S genes could accurately discriminate the G6 genotype, but they were not able to differentiate between G1 and G3 genotypes. As the G1 and G3 genotypes belong to the E. granulosus sensu stricto, low intra-species variation was observed for act II and 12S. The atp6 gene could identify the G3 genotype but could not differentiate G6 and G1 genotypes. Using concatenated sequence of five genes (cox1 + nad1 + atp6 + 12S + act II), genotypes were identified accurately, and markedly higher resolution was obtained in comparison with the use of reference markers (nad1 + cox1) only. Application of multilocus sequence analysis (MLSA) to large-scale studies could provide valuable epidemiological data to make efficient control and management measures for cystic echinococcosis.