Biofilm Formation Capability of Clinical Helicobacter pylori Isolates on MKN-45 Cells

Background: In vitro biofilm formation of H. pylori is demonstrated; however, its potential role in the persistent infection of the human stomach has not yet been addressed. Objectives: The aim of this study was to assess the biofilm formation of clinical H. pylori isolates on an epithelial cell line, a line that produces mucin. Methods: H. pylori isolates consisting of an efficient (19B) and a weak (4B) biofilm formation ability, were selected from screening of the clinical isolates. Their adhesion index was determined after 2h incubation with the semi-confluent monolayers of MKN-45 cells. Their biofilm formation was evaluated after 24 and 72 h incubation with MKN-45 cells using a modified adherence assay developed in this work. Production of biofilm was quantitatively assessed by CFU enumeration and qualitatively by the immunofluorescence, and scanning-electron-microscopic (SEM) methods. Due to the importance of mucin in the binding of H. pylori and biofilm formation, the binding strength of the mucin binding protein, MUC5AC, and MUC1 with docking was investigated using cluspro webserver. Results: Using MKN-45 epithelial cell line as a model, significant differences were observed between the adhesion index of 19B and 4B isolates. After 24h, both isolates were able to form biofilms with significantly higher numbers of CFU for the 19B isolate. These results were confirmed by immunofluorescence and SEM such that after 24h, a cluster of coccoid bacteria on the MKN-45 cells in the form of microcolonies was observed. The docking results showed that MUC5AC demonstrated the most favorable interaction with H. pylori urease and BabA with docking energy scores of -931.1 and -906.3 kcal.mol-1, respectively. Conclusions: By developing an appropriate in situ biofilm assay, we investigated biofilm formation by clinical H. pylori isolates on the MKN-45 epithelial cell line. The establishment of such an in-situ model for studying the biofilm formation ability of clinical isolates can also be used to study cell-bacteria interactions in the context of a complex biofilm and also as a model for drug screening applications.