Purpose. Targeted delivery of rifampicin loaded microspheres to the alveolar macrophage, the host cell for Mycobacterium tuberculosis (MTB), may be an effective targeted approach to pulmonary tuberculosis therapy. A guinea pig infection model has been adopted as a post-treatment screening method for antimicrobial effect. Insufflation and nebulization methods of drug delivery were evaluated. Methods. Rifampicin alone (RIF, 1.03-1.72 mg/kg), within poly(lactide-co-glycolide) microspheres (R-PLGA, equivalent to 1.03-1.72 mg/kg) or polymer microparticles alone (PLGA) were administered by insufflation or nebulization, 24 It before bacterial aerosol exposure. Animals were infected with an aerosol containing a small number (2 x 10(5) cfu/mL) of virulent H37Rv strain of MTB. Lung and spleen tissue samples were collected 28 days after infection for quantitative bacteriology and histopathological analysis. Results. There was a dose-effect relationship between insufflated R-PLGA and burden of bacteria in the lungs. In addition, guinea pigs treated with R-PLGA had a significantly smaller number of viable, bacteria (P<0.05), reduced inflammation and lung damage than lactose or saline control, PLGA or RIF treated animals. Conclusions. These studies indicate the potential of R-PLGA, delivered by insufflation or nebulization directly to the lungs, to affect the early development of pulmonary TB
