Antibody response to Prevotella spp. in patients with ventilator-associated pneumonia

Although anaerobic bacteria are frequently isolated from the oropharyngeal flora, their potential pathogenic role in ventilator-associated pneumonia (VAP) has been poorly investigated. In order to evaluate the pathogenic role of Prevotella spp. isolated from protected specimen brushes, we investigated the systemic humoral response with the enzyme-linked immunosorbent assay (ELISA) and Western blot (immunoblot) in 13 patients who developed a VAP associated with Prevotella species (group I). The antigen used was a mixture of whole-cell proteins taken from four reference Prevotella strains. We compared the antibody levels observed in these patients with those measured in 30 patients who developed a VAP unrelated to anaerobic bacteria (group II), in 27 patients with dental stumps (group III), and in 30 healthy patients (group IV) who had Prevotella species on dental plaque. The ELISA levels obtained in the four groups showed significant differences between group I and each of the three control groups (P < 0.05). The antibody profiles obtained by Western blot showed an intensity of response roughly superposable over levels obtained by ELISA and a species specificity. These findings suggested that colonization of these patients with Prevotella species may have been associated with an infectious process leading to a systemic humoral response and that these bacteria could play a role in VAP.