Identification of genotypes of Giardia duodenalis human isolates in Isfahan, Iran, using polymerase chain reaction – Restriction Fragment Length polymorphism

BACKGROUND: Giardia duodenalis is one of the most prevalent intestinal parasites of human. It also infects a wide range of mammals. Two genotype of G.duodenalis (A and B) were commonly reported among humans with different frequency of distribution in different geographical locations. This work was conducted to discriminate genotypes of Giardia duodenalis human isolates in Isfahan city using PCR- RFLP. This is the first molecular study on human isolates of G.duodenalis in the area. METHODS: Samples were collected from different health centers of Isfahan city during June 2011 and February 2012. From 175 Giardia positive stool samples 67 specimens were selected randomly. Cysts of Giardia positive samples were concentrated by flotation sucrose. Extraction of genomic DNA from trophozoite and cysts was performed using QIAamp Stool Mini kit with a modified protocol. PCR- RFLP method was used to amplify a fragment of 458bp at the glutamate dehydrogenase locus, and restriction enzymes BspLI and RsaI differentiated human genotypes A and B and their subgroups. RESULTS: PCR – RFLP assay of 67 isolates showed 40(59.7%) isolates as Genotype A group II, 23(34.32%) samples as Genotype B Group III and two (2.98%) sample as Genotype B group IV. Mixed genotype of (AII and B) was detected only in two isolates (2.98%). CONCLUSIONS: PCR – RFLP assay targeting gdh locus is a sensitive tool and discriminates genotypes, sub genotypes and mixed type of G.duodenalis. Results of our study suggest both anthroponotic and zoonotic origins for the infections respectively.