Molecular detection and subtype distribution of Blastocystis in hospitalized patients with gastrointestinal cancer and polyps in Hainan, China.

Blastocystis is a ubiquitous intestinal microeukaryote with controversial pathogenic potential. Epidemiological data on Blastocystis in patients with gastrointestinal neoplasms remain limited, especially in tropical regions of China. This study aimed to determine the prevalence and molecular subtype distribution of Blastocystis in hospitalized patients with gastrointestinal cancer or polyps in Hainan Province. A descriptive cross-sectional study was conducted at a tertiary hospital in Hainan. A total of 509 consecutive patients were enrolled, including 357 with pathologically confirmed gastrointestinal cancer and 152 with gastrointestinal polyps. Blastocystis was detected by nested PCR targeting the SSU rRNA gene, and positive amplicons were sequenced for subtype identification. The overall detection rate of Blastocystis was 2.2% (11/509) in gastrointestinal tumor patients, with 1.7% (6/357) and 3.3% (5/152) in gastrointestinal cancer and polyp patients, respectively. Three subtypes (STs) were identified: ST3 (n = 7, 63.6%), ST1 (n = 2, 18.2%), and ST7 (n = 2, 18.2%). ST1 and ST3 are known to circulate widely in human populations, while ST7 is primarily an avian-adapted subtype with occasional zoonotic potential. An exploratory analysis suggested a possible age-dependent colonization pattern in polyp patients (uncorrected P = 0.003), but this finding requires validation in larger cohorts due to the small sample size. This study provides baseline data on Blastocystis subtype distribution in gastrointestinal disease patients in Hainan. Further well-designed studies with appropriate control groups and rigorous control for confounding factors are required to clarify the clinical significance of Blastocystis colonization in this patient population.