A model of pneumococcal pneumonia in chronically intoxicated rats

To determine the role of chronic ethanol intoxication on the pathogenesis of pneumococcal pneumonia, male Sprague-Dawley rats were fed an ethanol-containing diet for 1 week before intratracheal challenge with type 3 Streptococcus pneumoniae and for 10 days after infection. Control rats were fed the same diet except that ethanol was replaced isocalorically with carbohydrate. Ethanol treatment increased pneumococcal bacteremia, levels of capsular polysaccharide antigenemia, and susceptibility to lethal pneumonia. Once dissemination occurred, ethanol-fed rats failed to eliminate pneumococci from the bloodstream. Ethanol-fed rats demonstrated a defect in late pulmonary clearance of pneumococci that was temporally associated with a significantly higher pneumonia severity index. Pneumonia was characterized by an intense polymorphonuclear leukocyte infiltration, severe edema, and a fibrous exudate. Bronchoalveolar lavage confirmed the heightened inflammatory response in the lungs of ethanol-fed rats, suggesting that chronic ethanol intoxication did not impair polymorphonuclear leukocyte recruitment but may alter their antipneumococcal functions.