In vivo study on the immunomodulating effects of OM-85 BV on survival, inflammatory cell recruitment and bacterial clearance in Klebsiella pneumonia

Oral administration of the bacterial extract OM-85 BV has been shown to prime alveolar macrophages (AM) in such a way that they secrete significantly more nitric oxide, tumor necrosis factor-alpha and interleukin-1beta upon in vitro stimulation with lipopolysaccharide (LPS). As increased cytokine secretion by AM may account for the therapeutic effect of OM-85 BV in respiratory tract infections, we studied the effect of orally administered OM-85 BV on the outcome of Klebsiella pneumoniae-induced pneumonia. Mice received a daily oral dose of OM-85 BV (350 mg/kg body weight) for 5 days and were intratracheally infected with 333, 1000 or 3333 CFU K. pneumoniae on day 8. It was shown that OM-85 BV pretreatment of mice has no effect on bacterial clearance, neutrophil recruitment and survival in this acute respiratory tract infection. Also, OM-85 BV treatment had no protective effect in a recurrent infection with K. pneumoniae. It is concluded that AM activation by oral treatment with OM-85 BV is not sufficient to play a protective role in respiratory tract infection with K. pneumoniae.