The lack of MeOPN modification affects the number of intracellular C. jejuni in macrophages. Chicken or human macrophages were incubated with C. jejuni 11168H (WT), Δcj1417 (MeOPN) and Δcj1439 (capsule) mutant at MOI 50 for 30 min. Intracellular bacteria were assessed by a gentamicin protection assay, and counted at 0 h after removal of gentamicin (T0, open bar) and after a further 3 h (T3, closed bar) of incubation. The average number of colonies at T0 and T3 are presented as Log10 CFU/mL (A). The percentage of killed bacteria was calculated using the average number of colonies at T0 and T3 (B). Each bar represents mean of three independent experiments and error bars are the standard deviation of three independent experiments. Asterisks indicate a statistically significant difference of the number of survived bacteria (A) and the percentage of killed bacteria (B) in different treatment (P < 0.05).