Studies on the Fate of Living Bacteria Introduced Into the Upper Respiratory Tract of Normal and Intranasally Vaccinated Rabbits

Summary and Conclusions A study was made of the fate of living bacteria instilled intranasally into normal and intranasally vaccinated rabbits. Similar experiments were also performed on normal rabbits and guinea pigs in which suspensions of inert particles were instilled into the nostrils and their distribution within the lungs determined. The results may be summarized as follows: Non-virulent staphylococci, when instilled intranasally into normal rabbits in relatively small volumes of fluid, pass quickly and directly into the lungs by way of the trachea and bronchi.Virulent pneumococci, when instilled intranasally into normal animals, do not pass directly through the epithelium of the upper respiratory tract, but are aspirated into the lungs and thence enter the blood. They may pass directly through the epithelium of the upper respiratory tract when introduced into rabbits kept in abnormal positions and under prolonged anesthesia.Intranasal vaccination with a formalin-killed suspension of type 1 pneumococci does not prevent the pulmonary aspiration of intranasally instilled type 1 pneumococci, but restricts their dissemination from the lungs to the blood and inhibits their growth both in the lungs and in the body as a whole.Inert particles introduced into the nostrils of normal rabbits and guinea pigs readily reach the lungs by direct aspiration. Their localization within the lungs depends mainly upon gravity and inspiratory suction, as suggested previously by Corper and Robbin.