Characterization of a Helicobacter pylori strain with high biofilm-forming ability

Abstract

Introduction. Helicobacter pylori is highly polymorphic, and some strains are much more likely to cause disease than others. Biofilm formation can help bacteria to survive antibiotic treatment, immune attack and other stresses, promoting persistent infection. Hypothesis/Gap Statement. We hypothesized that H. pylori isolates from patients with more severe H. pylori-associated disease would be better at forming biofilms than isolates from patients with less severe disease. Aim. We initially aimed to determine whether or not the biofilm-forming ability of H. pylori isolates was associated with disease in the UK-based patients from whom the bacteria were isolated. Methodology. Biofilm-forming ability of H. pylori isolates was determined using a crystal violet assay on glass coverslips. The complete genome sequence of strain 444A was generated by hybrid assembly of Nanopore MinION and Illumina MiSeq data. Results. Although we found no associations between biofilm-forming ability of H. pylori and disease severity in patients, we discovered that strain 444A had particularly high biofilm-forming ability. This strain had been isolated from a patient with gastric ulcer disease and moderate to severe scores for H. pylori-induced histopathology. Analysis of the genome of the high biofilm-forming H. pylori strain 444A revealed that it possesses numerous biofilm- and virulence-associated genes and a small cryptic plasmid encoding a type II toxin–antitoxin system. Conclusion. There is substantial variation in biofilm-forming ability in H. pylori, but this was not significantly associated with disease severity in our study. We identified and characterized an interesting strain with high biofilm-forming ability, including generation and analysis of the complete genome.