Facilitated expansion of pneumococcal colonization from the nose to the lower respiratory tract in mice preinfected with influenza virus

A strain of Streptococcus pneumoniae, when inoculated intranasally in 2 mu l of suspension into BALB/c mice preinfected with influenza virus, colonize d first in the nose, and several days thereafter also colonized significant ly in the trachea and lungs with purulent inflammation, Pneumococcal coloni zation was also observed in the noses of normal mice after the same bacteri al inoculation, but not apparently in the lower respiratory tract. These re sults suggest that pneumococcal infection may develop from the upper to the loner respiratory tract as a possible sequence preferentially in influenza virus-infected subjects.