Group B streptococcal type Ia sepsis in mice after intranasal inoculation and the effect of infection on lungs.

The intranasal inoculation of adult mice with saline suspensions of virulent group B streptococci serotype Ia resulted in septicemia which was lethal. Decreasing the inoculation dose of streptotocci increased the time required for their appearance in the blood and the mean time to death of the mice. Before the appearance of septicemia, the number of organisms in the lungs decreased to about 1% of the inoculation dose, and the majority could be recovered by lavage of the lungs through the trachea. In contrast, most of the organisms remained in the lavaged lungs of bacteremic mice after intranasal or intravenous inoculation. Lung surfactant obtained from infected mice was altered by a reduction in lipid and by an increase in protein. The organisms in vitro did not attack surfactant lipid labeled with [1-14C]palmitic acid, but their pathogenesis in vivo affected the permeability of the air-blood barrier, as shown by the leakage into the air spaces of plasma albumin labeled by the intravenous injection of Evans blue dye.