Detection of strain types and analysis of risk factors among subjects from Hainan Province, China.

Objective: To explore the prevalence of type I and type II infection and investigate risk factors in a population from Hainan Province in China.

Methods: Data came from a large, cross-sectional study conducted from August 2022 to April 2023 involving five cities of Hainan. Subjects with confirmed 14C-urea breath test (UBT) and positive serological assay were included. All subjects had a gastroscopy. According to presence or absence of CagA/VacA proteins, subjects were classified as either type I (present) or type II strains (absent). Gastroscopic findings and several socio-demographic factors were examined for correlation with antibody serotyping.

Results: In total, 410 subjects were investigated for strain types. The overall prevalence of the highly virulent, type I strain was 79% (324/410) and type II strain was 21% (86/410). There was a strong association between type I strain and peptic ulcer disease. Of several sociodemographic factors investigated, only smoking and data over baseline (DOB) values showed significant differences between type 1 and type II strains. Logistic regression analysis showed a lower risk of type I infection in smokers compared with non-smokers, and a higher risk of type I infection in subjects with medium and high data over baseline (DOB) values compared with subjects who had low DOB values.

Conclusion: Highly virulent, type I infections predominate in Hainan and the co-positivity of CagA and VacA antibodies are related to type I infection. We found that Type I was closely associated with peptic ulcer disease and the DOB values were generally high.