Fig. 4

Invasion of primary caecal chicken cells by Campylobacter jejuni chicken strains. Invasion levels of primary caecal cells by C. jejuni strains using the gentamicin protection assay. The error bars represent the SEM. The horizontal dashed lines represent the control strain 81–176 and its SEM. Strain results were classified by increasing order. The x axis represents the strains numbered according to their final mean rank value, presented in Table 1. Strains were found with different invasion properties (Kruskal-Wallis, p < 0.0001). Invasion is expressed as −1/log (invading bacteria/initial bacteria used)