flaA mRNA transcription level correlates with Helicobacter pylori colonisation efficiency in gnotobiotic piglets.

In-vivo passage of the gastric pathogen Helicobacter pylori in gnotobiotic piglets results in a greater colonisation efficiency in subsequent infections. The rate of colonisation steadily increases with the number of passages. To determine if this increased efficiency is related to the level of expression of flaA, a gene which encodes the major subunit of flagella, this study evaluated the level of flaA expression at five points during serial in-vivo passage of strain 26695. Semi-quantitative reverse transcriptase polymerase chain reaction and Northern dot-blot analysis of flaA mRNA levels (expressed as a ratio to the level of ureA mRNA) revealed a positive correlation between flaA expression and colonisation efficiency; flaA mRNA levels increased incrementally with in-vivo passage as did colonisation rates. Immunoblots of outer-membrane vesicles from pig-passaged and laboratory-passaged strains also demonstrated marked differences in the amount of flagellin present in poor and efficient colonisers.