Heterogeneity of Helicobacter pylori cag genotypes in experimentally infected mice

Our aim was to assess whether the Helicobacter pylori population recovered from experimentally infected mice show heterogeneity in cag genotypes. Wild -type FVB/N mice were challenged with strain Hp I and sacrificed 8 weeks la ter. Direct PCR on gastric tissue was performed using primers for glmM and cagA, and for these two genes and for cagE and virB11 using DNA from the in fecting and the emerging strains. The gastric tissues of two of five mice w ere PCR+ for glmM but not cagA. For the infecting strain, the PCRs for all four genes studied were strongly positive, but the sweeps from the emerging strains from both mice gave weaker signals for cagA and cagE. Examination of single colonies showed reduced or absent signals for cagA and cagE in re lation to glmM and virB11. Serial dilution PCR of sweep isolates from the m ice showed a 10- to 100-fold decrease in cagA signal compared to the infect ing strain. The decrease of cagA and cagE, but not vif-B11, amplification a nd lack of cagA hybridization in Southern blots indicates a selective loss of the right half of the cag island during murine infection. This phenomeno n is consistent with host-induced adaptive changes of cag genotype in the p opulation of colonizing H. pylori cells. (C) 2001 Published by Elsevier Sci ence B.V. on behalf of the Federation of European Microbiological Societies .