Young cultures of B. influenzæ, subcultured only once after isolation from early cases of influenza, were used. The microorganism was recovered in abundance by throat swab two days later and again from the bronchus at autopsy three days after inoculation. Tuberculosis of mesenteric lymph nodes, of intestine and of liver and several small tuberculous nodules in the lung were found at autopsy. A secondary invasion of the lung by staphylococci had occurred. There was bronchitis with an inflammatory infiltration of the subepithelial tissue of the bronchi by lymphoid and plasma cells. Bronchopneumonia was present, and the bronchi and many of the alveoli contained blood. These changes do not differ essentially from the changes found in many instances of pneumonia following influenza.
In three instances cultures of B. influenzæ were injected into the trachea by means of a hypodermic syringe.
In one of these experiments (Experiment 4) intratracheal injection of 2 c.c. salt solution suspension of B. influenzæ (isolated at autopsy from bronchus of the monkey used in Experiment 3), representing growth on 1½ blood agar plates, was made with a needle inserted into trachea just above the suprasternal notch. On the following day a throat culture contained B. influenzæ in abundance. Three days after inoculation the monkey appeared to be very sick and there was profuse nasal discharge. The animal coughed and sibilant râles were heard over the chest. There was no leucocytosis. A throat culture contained B. influenzæ. Four days after inoculation the monkey was still sick and weak, but appeared much improved and was killed. The trachea and large bronchi contained thick viscid mucus. In the middle lobe of the right lung was a patch of grayish red, airless tissue, firmer than the lung substance elsewhere. Cultures from the trachea, bronchus and lung contained a variety of microorganisms, but B. influenzæ was not recovered.
In two additional experiments (Experiments 6 and 7) cultures of B. influenzæ forty-eight hours old were injected into the trachea of monkeys. The microorganism was recovered in cultures made from the pharynx two days later. These animals were only slightly sick.
Introduction of B. Influenzæ and S. Hemolyticus into the Trachea.—In view of the frequent association of B. influenzæ and S. hemolyticus in the sputum of patients with streptococcus pneumonia following influenza and in the bronchi and lungs of those who have died with this disease, the two microorganisms were injected simultaneously into the trachea of monkeys.
B. influenzæ and S. hemolyticus in Experiment 7 produced bronchitis and bronchopneumonia. There was acute inflammation of the interstitial tissue of the lung, and acute lymphangitis with numerous polynuclear leucocytes within the lumen of the lymphatics was present. B. influenzæ and S. hemolyticus were present in the trachea at autopsy four days after inoculation. It is probable that part of the injected culture entered the tissue outside the trachea, for an abscess was formed in this situation. It is noteworthy that acute pericarditis occurred and both S. hemolyticus and B. influenzæ were found in the pericardial exudate. B. influenzæ not infrequently exhibits this tendency to penetrate in association with other bacteria localities which it does not invade independently.
In a second experiment (Experiment 8) in which B. influenzæ and S. hemolyticus were injected into the trachea, both microorganisms were recovered from the throat on the day following inoculation; on the fifth day S. hemolyticus alone was recovered and on the sixth day a throat culture was negative both for S. hemolyticus and B. influenzæ.
Introduction of B. influenzæ and of Pneumococcus or of Pneumococcus Alone into the Trachea.—In two experiments B. influenzæ and Pneumococcus Type III were simultaneously injected into the trachea.
In Experiment 9 a large male monkey was used and intratracheal injection made with syringe and needle of 5 c.c. salt solution suspension of Pneumococcus Type III and B. influenzæ (growth on 5 blood agar plates of mixed cultures of Pneumococcus III and B. influenzæ). On the following day the animal was very sick, lying on the floor of its cage, and was dead two days after inoculation.
The dosage of bacteria in this experiment was large. The lesions in gross appearance and microscopically resembled those seen in many instances of pneumonia following influenza. In the trachea there was loss of ciliated epithelium, congestion of the subepithelial tissue, hemorrhage and infiltration with plasma cells. The lungs were consolidated and red and there were hemorrhage and edema. B. influenzæ, as in human cases, was abundant in the bronchi, less abundant in the consolidated lung, being present though scant in the left lung, and absent in cultures from the right. B. influenzæ as in Experiment 8 with streptococcus had entered the left pericardial cavity in company in this experiment with Pneumococcus III.