Importance of the bacterial neuraminidase for P. multocida infection. Filter-grown ALI cultures were infected by P. multocida (inoculation with 102 CFU for 1 h). The importance of the bacterial neuraminidase was analyzed by pretreating some samples with neuraminidase from C. perfringens and by incubating some of the other samples in the presence of the neuraminidase inhibitor DANA. At 4, 12, 24 hpi, samples were immune-stained (anti-β-tubulin, DAPI) to visualize cilia (red) and nuclei (blue). A Pictures obtained by microscopy; B Quantitation of the relative red fluorescence. Results are presented as mean ± SEM compared to mock-infected samples.