Aras Part Medical International Press International Journal of Medical Parasitology and Epidemiology Sciences 2766-6492 7 2 2026 06 29 Molecular Identification of human Blastocystis isolates in patients of Al-Diwaniyah Teaching Hospital, Iraq 61 66 10.34172/ijmpes.6249 EN Rana Saleh Al-Difaie https://orcid.org/0000-0002-2081-0479 Khawla Hussien Sabbar Hiba Shehab Ahmed Journal Article 10.34172/ijmpes.6249 2026 03 14 2026 05 28 Introduction: The human large intestine is inhabited by the anaerobic, eukaryotic, unicellular protozoan B. hominis, which is found worldwide. This study sought to examine the existence and molecular characteristics of this parasite in adult patients admitted to Al-Diwaniyah Teaching Hospital in Al-Diwaniyah Governorate from February to December 2025. Methods: The parasitic infection was not recognized by microscopic examination at the hospital, but it was confirmed using PCR targeting the 16S rRNA gene as a DNA marker to assess the prevalence of B. hominis. Results: The overall prevalence of the parasite was 3.1%. Hence, PCR analysis was more sensitive than microscopic analysis. The 18S rRNA gene of the local isolates was matched to the worldwide reference strains of B. hominis listed in the GenBank. Regarding mutation, the alignment analysis revealed the substitution mutations alignment similarity in the 18S ribosomal RNA gene between the local B. hominis H isolates and Global, where a (0.35%,0.29%,0.85%,0.85%) match was found between the local isolates and an earlier reported B. hominis isolates from Spain, China, Thailand, and Denmark, respectively. The local strains shared (99.65, 99.71, 99.15, 99.15) % of their identity with isolates from Spain, China, Thailand, and Denmark, respectively. Conclusion: phylogenetic (evolutionary) analysis of a parasite is a vital tool for precisely identifying the microorganism and understanding its evolutionary relationships thereby enabling the development of effective therapeutic and preventive strategies based on the microbe’s origins and genetic evolution.