ESTABLISHMENT OF A STREPTOCOCCUS-PNEUMONIAE NASOPHARYNGEAL COLONIZATION MODEL IN ADULT MICE

Human nasopharyngeal carriage of Streptococcus pneumoniae constitutes the major natural reservoir of pneumococci and is thought to be the pr elude to virtually all pneumococcal disease. If carriage could be grea tly reduced, pneumococcal transmission and disease could be largely el iminated. To facilitate the studies of mechanisms important in carriag e and to identify immunogens that can elicit protection against carria ge, we characterized an adult mouse model of nasopharyngeal carriage. Non-anaesthetized mice were inoculated intranasally with pneumococci i n 10 mu l of fluid. Nasopharyngeal carriage was observed with strains of capsular types 3, 4, 6A, 6B, 14, 19, and 23. Carriage was stable ov er time, and the numbers of pneumococci carried were relatively indepe ndent of inoculation dose; findings which indicate that the recovery o f pneumococci from 1 day to 2 weeks post inoculation was dependent on colonization, rather than just temporary contamination. To ensure carr iage in the largest percentage of mice, without causing sepsis or deat h, inoculations of 10(7) colony forming units (cfu) should be used. In this model, carriage was generally observed without concomitant bacte remia or sepsis and carriage was observed even with strains that were avirulent when injected i.v. The model should be useful for the identi fication of protection-eliciting antigens, since intranasal immunizati on with heat-killed pneumococci or lysates of pneumococci protected ag ainst carriage. (C) 1997 Academic Press Limited.