Molecular characterization and phylogenetic analysis of Microsporidia and Cryptosporidium spp. in patients with multiple bowel biopsies from Fars Province, Iran.

Microsporidia and Cryptosporidium species are prominent agents of enteritis, capable of causing severe chronic diarrhoea in children, immunocompetent and immunocompromised individuals around the world. It is not possible to identify the parasites at species level solely on the basis of microscopy. The aim of the present study was to identify and characterize the species of Microsporidia and Cryptosporidium in immunocompetent humans with GI disturbances by nested PCR-RFLP, sequencing, and phylogenetic analysis. Fresh frozen and fresh paraffin-embedded biopsy specimens of the duodenum, jejunum, ileum and the cecum of 110 patients were examined. Genomic DNA was extracted from all bowel biopsies. Nested PCR targeting the 18S rRNA gene was performed by restriction endonuclease digestion of the PCR product followed by nucleotide sequencing and phylogenetic analysis. A total of three patients with chronic diarrhoea were positive for Microsporidia and Cryptosporidium spp. Species analysis showed the presence of C. parvum and E. bieneusi in two and one samples, respectively. This is the first PCR confirmation of the presence of E. bieneusi and C. parvum in a bowel biopsy of immunocompetent individuals in Iran. This study revealed that PCR, sequencing, and phylogenetic analysis are very powerful tools for the precise species identification of these pathogens.