Infection with cagA- and vacA-positive and -negative strains of Helicobacter pylori in a mouse model

To study the role of cytotoxin-associated protein (cagA) and vacuolating cy totoxin (vacA) in Helicobacter pylori infection in an experimental murine m odel, mice were infected with seven strains with different cagA and vacA st atus. Groups of 10 NMRI mice were challenged and were killed 5 weeks later. In a second study, 20 mice were challenged with a mixture of the same seve n strains and killed 1, 3, 15 and 17 weeks post-inoculation. All seven stra ins were found to colonize the mice for the 5-week experimental period. Ani mals infected with vacA-positive strains, regardless of cagA status, showed an elevation of antibody titers. Two cagA-negative and vacA-positive strai ns and one cagA- and vacA-positive strain were found to 'take over' in the mixed infection as analyzed by the randomly amplified polymorphic DNA-polym erase chain reaction technique and in one mouse stomach we found coexistenc e of two of the strains. We found no evidence of the different strains colo nizing different parts of the stomach. (C) 2001 Federation of European Micr obiological Societies. Published by Elsevier Science B.V. All rights reserv ed.