Blastocystis subtypes in cancer patients: Analysis of possible risk factors and clinical characteristics.

The aim of the present study was to examine the frequency and genetic diversity of Blastocystis in cancer patients of a Medical Oncology Department in Aydın, Turkey. Patients' stool samples were examined between January 2013 and February 2014 by both microscopy and culture methods. Culture positive samples were subjected to DNA isolation and Sequence Tagged Site (STS)-PCR analysis. Possible etiological factors and clinical features of Blastocystis infection were also analyzed and compared between Blastocystis infected and non-infected subgroups. Blastocystis was detected in 15 (6.5%) of 232 stool samples by microscopy and in 25 (10.8%) by culture methods. Out of 25 culture positive isolates, the most prevalent subtype was ST3 (59%), followed by ST1 (23%) and ST2 (18%). Blastocystis frequency was higher in the male patients than the females (19% vs. 6.5%, p<0.05) and in the patients living in urban areas than rural (15.3% vs. 6.6%, p<0.05). Interestingly, Blastocystis was more frequent in patients with lung cancer than the other cancer types (χ2=18, p<0.05) and also in the patients who had received at least eight chemotherapy cycles than fewer (21.4% vs. 9.9%, p<0.05). The rate of gastrointestinal symptoms was not significantly different between infected and non-infected cases. The pathogenic and clinical impacts of Blastocystis in cancer patients should be further examined, particularly as relates to treatment, microbiota and cancer type.