Helicobacter pylori biofilm formation and CagA-associated alteration in gastric mucin expression: Implications for bacterial persistence.

BACKGROUND

H. pylori is a major gastric pathogen associated with chronic gastritis, peptic ulcers and gastric malignancies. Two important mechanisms contributing to its persistence are biofilm formation and modulation of host epithelial responses. This study aimed to evaluate the biofilm-forming capacity of clinical H. pylori isolates, assess the effect of proteinase K on biofilm formation and investigate differences in mucin expression following infection with CagA-positive and CagA-negative clinical isolate on mucin expression in gastric epithelial cells.

MATERIALS AND

METHODS

The biofilm-forming capacity of 21 clinical H. pylori isolates and the disruptive potential of proteinase K (50 and 200 μg/ml) was assessed with the crystal violet assay, and the potential cytotoxic effect of proteinase K on AGS cells was assessed by XTT assay. The effect of CagA- positive and CagA negative clinical isolates on mucin expression (MUC5AC, MUC5B, and MUC6) was tested in AGS gastric epithelial cells via immunofluorescence staining and quantitative RT-PCR.

RESULTS

Most isolates (90.5%) were capable of forming biofilm, with nearly half classified as strong biofilm producers. Treatment with proteinase K significantly reduced biofilm biomass in a concentration-dependent manner, with the higher concentration (200 μg/ml) causing an approximately 80% reduction in biofilm formation. Importantly, proteinase K did not significantly affect AGS cell viability. Infection of AGS cells with CagA-positive H. pylori isolates resulted in increased expression of MUC5AC and MUC5B, while MUC6 expression remained largely unchanged. In contrast, infection with CagA-negative isolates led to decreased MUC5AC and MUC5B expression and a slight increase in MUC6 levels.

CONCLUSIONS

These findings demonstrate substantial biofilm-forming capacity among clinical isolates and an association between CagA- positive isolates and distinct patterns of gastric mucin expression. The potential biological relationship between these phenotype and H. pylori persistence remains to be established in mechanistic studies.