FIGURE 7.

Effect of OAP levels on C. jejuni host-bacteria interactions. A, Δape1 shows reduced chick colonization compared with wild-type strain 81-176, whereas ΔpatB, ΔpatA, and Δoap mutants display wild-type colonization. Each point represents the recovery of C. jejuni strains in log CFU/g of cecal contents from individual day-old chicks 6 days post-colonization with 1 × 10⁴ CFU/ml of the indicated strain. The geometric mean is denoted by a black bar. Error bars represent 95% confidence intervals. Adherence, invasion, and intracellular survival of C. jejuni in INT407 epithelial cells were assessed by a Gm protection assay and OAP mutant strains. Δape1 (B) shows a reduced ability to adhere to, invade, and survive in INT407 epithelial cells that were restored upon complementation (C). ΔpatB (D), ΔpatA (E), and Δoap (F) exhibit near wild-type adherence, invasion, and intracellular survival properties. INT407 cells were infected with C. jejuni at a multiplicity of infection of ∼80. Adherence and invasion were quantified at 3 h post-infection. At this point, the media in the remaining wells were replaced with MEM containing gentamicin (150 μg/ml) and incubated for 2 h, after which the amount of bacterial cells that had invaded the epithelial cells was measured (5-h invasion time point). The Gm in the remaining wells was washed off, and the cells were incubated with fresh MEM containing 3% FBS and a low dose of Gm (10 μg/ml) for an additional 3 h (8-h intracellular survival time point). CFU/ml was determined for each well by lysing the cells with water and plating the dilutions onto MH-TV plates. Results for B and C are representative of three independent experiments performed in biological triplicate. The data in D, E, and F are representative of two independent experiments performed with three biological replicates. G, INT407 epithelial cells secrete less IL-8 upon infection with Δape1 than wild type. Results are from one representative experiment of three independent experiments performed in triplicate. Error bars represent the standard deviation. *, denotes statistically significant difference using the unpaired Student's t test, with *, **, and **** indicating p < 0.05, p < 0.01, and p < 0.00001 respectively.