Cytokine kinetics and other host factors in response to pneumococcal pulmonary infection in mice

Immunomodulating effects of HMR 3004 on pulmonary inflammation caused by heat-killed Streptococcus pneumoniae in mice

We investigated the influence of HMR 3004, a new ketolide antibiotic, on the pulmonary inflammation induced by heat-killed fluorescein isothiocyanate-labeled Streptococcus pneumoniae. HMR 3004 downregulated (P < 0.05) the pneumococcus-induced release of interleukin-6 (IL-6), IL-1beta, and nitric oxide in bronchoalveolar lavage fluid. The drug limited (P < 0.05) neutrophil recruitment to lung tissues and alveoli but did not interfere with phagocytosis. HMR 3004 totally abrogated lung edema. By reducing inflammation in addition to possessing antimicrobial properties, HMR 3004 may participate in improving the outcome of bacterial pneumonia.

Reduction by cefodizime of the pulmonary inflammatory response induced by heat-killed Streptococcus pneumoniae in mice

It has recently become apparent that overwhelming inflammatory reactions contribute to the high mortality rate associated with pneumococcal infection in immunocompetent hosts. Cefodizime (CEF) is an antibiotic that seems to be endowed with immunomodulating properties. To investigate the influence of CEF on the pulmonary inflammatory response induced by Streptococcus pneumoniae, we infected mice with repeated intranasal inoculations of 10(7) CFU of heat-killed fluorescein isothiocyanate-labeled bacteria, which are insensitive to the killing properties of the drug. CEF downregulated but did not abolish the strong polymorphonuclear leukocyte (PMN) recruitment induced by S. pneumoniae. PMN recruitment was not primarily mediated by leukotriene B4 in this model. The drug did not interfere with intrinsic mechanisms of phagocytosis by PMNs and alveolar macrophages. CEF totally abrogated the pneumococcus-induced tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6) secretion in bronchoalveolar lavage fluid. The drug also prevented IL-6 release in lung homogenates and partly inhibited TNF-alpha, but it did not interfere with IL-1alpha secretion in the lungs of infected mice. The fractional and selective downregulation of inflammatory cells and cytokines by CEF suggests cell-specific and intracellular specific mechanisms of interaction of the drug. The immunomodulatory properties of CEF may help restrain excessive inflammatory reactions, thus contributing to the reported good clinical efficacy of the drug against lower respiratory tract infections.