<i>H</i>. <i>pylori</i> exerts intraspecies colonization resistance early in infection.

(A) Sequential infection schematic. Mice were infected with the initial strain for 1 week, challenged with the opposite-colored isogenic strain, and stomachs were harvested after 1 additional week for CFU enumeration of both initial and challenge strains and visualization of gland colonization by microscopy. As an example, Hp GFP was depicted as the initial strain and Hp tdT as the challenge strain in this diagram. However, the reverse experiment, in which Hp tdT was the initial strain and Hp GFP was the challenge strain, was also conducted. (B) Total CFU/g recovered from sequentially infected mice as depicted in panel A. Both iterations in which Hp GFP was either the initial strain (left) or challenge strain (right) are shown (five mice per group). Black dashed lines connect Hp GFP and Hp tdT counts recovered from the same mouse at 2 weeks post-inoculation of the initial strain. Gray dotted line, limit of detection. Relevant data values are included in S1 Data. (C) Three-dimensional confocal images of bacteria in glands from sequentially infected mice in panel B. GFP (green), tdT (red); scale bar, 30 μm. (D) Total CFU/g recovered from mice pre-colonized with Hp GFP for different time points (1, 3, 5, or 7 days) prior to challenge with Hp tdT (5–6 mice per group). Stomachs were harvested at 2 weeks post-inoculation of the initial strain for CFU enumeration of both initial and challenge strains. Data represent two independent experiments. Black dashed lines connect Hp GFP and Hp tdT counts recovered from the same mouse. Gray dotted line, limit of detection. Relevant data values are included in S1 Data. (E) Three-dimensional confocal images of bacteria in glands from sequentially infected mice in panel D, 2 weeks post-inoculation of the initial strain. GFP (green), tdT (red); scale bar, 30 μm. CFU, colony-forming unit; GFP, green fluorescent protein; tdT, tdTomato.