The effect of obesity on the coccoid form transformation of Helicobacter pylori and its relationship with gastric inflammation pattern: a retrospective comparative study

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BACKGROUND/AIM: Helicobacter pylori (H. pylori) can transform from its spiral form into a coccoid (viable but non-culturable; VBNC) state under adverse environmental conditions. The coccoid form is associated with antibiotic resistance and eradication failure. This study compared coccoid and spiral form proportions, H. pylori localization patterns (epithelial vs. crypt), and gastric inflammation parameters across three BMI-stratified groups. MATERIALS AND METHODS: This retrospective comparative study included 156 H. pylori-positive cases from the archives of Karamanoglu Mehmetbey University Faculty of Medicine (2016-2026). Groups: Group 1 (Severe obesity/Sleeve, BMI ≥ 35; sleeve gastrectomy, n = 55), Group 2 (Non-obese/Biopsy, BMI < 30; biopsy, n = 68), Group 3 (Obese/Biopsy, BMI ≥ 30; biopsy, n = 33). IHC with anti-H. pylori antibody was used for morphological assessment. Coccoid/spiral proportions, HP density, Sydney-criteria gastritis parameters, coccoid categorization (< 5%, 5-19%, 20-39%, ≥ 40%), and epithelial/crypt HP localization were analyzed (SPSS 25.0; p < 0.05). RESULTS: Median corpus coccoid proportion was significantly higher in Group 1 (10%, IQR 5-30) vs. Group 2 (1%, IQR 1-1; p < 0.001), with strong BMI correlation (r = 0.639, p < 0.001). The ≥ 40% coccoid category was exclusively observed in the severe obesity/sleeve group (23.6%; p < 0.001). Corpus spiral proportion decreased in a stepwise inverse gradient across categories (99%→90%→80%→40%; H = 113.8, p < 0.001). Corpus HP density (Sydney score) differed significantly across groups (H = 13.8, p = 0.001) and correlated positively with coccoid proportion (r = 0.267, p = 0.003). Corpus crypt H. pylori involvement differed significantly across groups (Group 1 41.8% vs. Group 2 29.2% vs. Group 3 11.1%; overall p = 0.045). In antrum, crypt involvement was higher in non-obese (36.8%) vs. obese biopsy patients (9.1%; p = 0.011). Coccoid proportion showed no significant correlation with patient age or inflammation grade. Multivariable logistic regression identified BMI as the sole independent predictor of corpus coccoid ≥ 10% (OR = 1.134 per 1 kg/m², 95% CI: 1.088-1.183, p < 0.001; C-statistic = 0.849), with age and sex non-significant after adjustment. CONCLUSION: Obesity was strongly associated with a coccoid-shifted H. pylori morphology (higher coccoid proportion) and with increased corpus crypt colonization. In this cohort the ≥ 40% coccoid category was observed exclusively in the severe obesity/sleeve group; this cut-off should be regarded as exploratory and hypothesis-generating, and requires external validation before it can be considered a histological signature of severe obesity. Because specimen type differed between groups and eradication outcomes were not assessed, these findings represent associations rather than causal relationships. IHC-based morphological assessment may be useful in obese and severely obese HP-positive patients, and prospective studies are warranted to determine whether coccoid burden and BMI can inform individualized eradication strategies.

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