Author(s): Mahmoudvand Hossein, Sepahvand Akram, Badparva Ebrahim, Khatami Mehrdad, Niazi Massumeh, Moayyed Kazemi Alireza*

Background: Recently, infection has been considered one of the most important causes of cancers because a large number of cases of cancer with infectious origin was reported. Objectives: The present investigation aimed to evaluate the prevalence and risk factors of Blastocystis hominis infection in patients with colorectal cancer in comparison to healthy individuals. Methods: The present descriptive case-control study was performed on 67 healthy individuals and 67 patients with colorectal cancers attending the general hospitals of Lorestan Province, Western Iran from October 2017 to August 2018. Colorectal cancers were diagnosed by an experienced gastroenterologist. A fresh stool specimen was collected from each subject in a sterile labeled container. The collected specimens were tested microscopically using saline and iodine wet preparations, then stained with trichrome stain according to the manufacturer’s instruction to find the cases of B. hominis forms. The DNA of the samples was extracted and specific primer-polymerase chain reaction (PCR) was performed. Results: Among the colorectal cancer patients, B. hominis was found in 16 (23.9%) patients, whereas of 67 healthy participants, 6 (9%) cases were found, indicating a significant difference (P < 0.001) in the prevalence B. hominis among the participants in the case and control groups. By the multifactorial logistic regression models, agriculture activity (0.24; 95% CI: 0.075 - 0.809), as well as consumption of unwashed fruit and vegetables (0.136; 95% CI: 0.040 - 0.459), were significantly related to the prevalence of B. homonis infection. All 22 positive samples (16 patients and 6 (9%) healthy people) were also positive by PCR method, indicating the presence of B. hominis and accuracy of microscopic examination, extraction, and PCR reaction. Conclusions: The obtained findings revealed that B. hominis may strongly link with human colorectal cancers given novel information about the important role of B. hominis in the progress of colorectal cancer. Nevertheless, more investigations are required to obtain accurate information about this suggestion.