Bacteriology of the Bronchitis of Influenza.—With the pneumonia of influenza, bronchitis is invariably present. Cultures have been made from the right or left main bronchus or from the very small bronchi which contained purulent exudate. A routine method of making the culture has been adopted. The right main bronchus, exposed by drawing the right lung out of the chest and toward the midline, was widely seared with a hot knife; the bronchus was partially cut across through the seared surface with a heated knife and a platinum needle inserted into the lumen. The bacteria obtained named in the approximate order of their relative frequency have been: B. influenzæ, pneumococci, hemolytic streptococci, staphylococci (aureus and albus), B. coli, S. viridans, M. catarrhalis, and diphthoid bacilli which have not been identified. Mixed infections occurred in most instances. The following list arranged by grouping bacteria in the order cited above, shows how varied have been the combinations which occur:
| B. influenzæ | 3 |
| Pneumococci | 5 |
| S. hemolyticus | 3 |
| Staphylococci | 3 |
| B. coli | 3 |
| S. viridans | 1 |
| B. influenzæ, pneumococci | 17 |
| B. influenzæ, S. hemolyticus | 18 |
| B. influenzæ, staphylococci | 4 |
| Pneumococci, S. hemolyticus | 1 |
| Pneumococci, staphylococci | 3 |
| S. hemolyticus, staphylococci | 4 |
| S. hemolyticus, B. coli | 2 |
| Staphylococci, S. viridans | 1 |
| B. influenzæ, pneumococci, S. hemolyticus | 6 |
| B. influenzæ, pneumococci, staphylococci | 15 |
| B. influenzæ, pneumococci, S. viridans | 2 |
| B. influenzæ, S. hemolyticus, staphylococci | 16 |
| B. influenzæ, S. hemolyticus, M. catarrhalis | 1 |
| B. influenzæ, staphylococci, S. viridans | 1 |
| Pneumococci, S. hemolyticus, staphylococci | 3 |
| Staphylococci, B. coli, S. viridans | 1 |
| B. influenzæ, pneumococci, S. hemolyticus, staphylococci | 7 |
| B. influenzæ, pneumococci, staphylococci, M. catarrhalis | 1 |
| B. influenzæ, S. hemolyticus, staphylococci, B. coli | 1 |
| B. influenzæ, S. hemolyticus, staphylococci, S. viridans | 1 |
| B. influenzæ, S. hemolyticus, staphylococci, M. catarrhalis | 1 |
| B. influenzæ, staphylococci, S. viridans, M. catarrhalis | 1 |
B. influenzæ has been present in the bronchi in 79.3 per cent of instances of pneumonia referable to influenza. Combinations which have been found most frequently are B. influenzæ and pneumococci (17 instances), B. influenzæ and hemolytic streptococci (18 instances), or the same combinations with staphylococci, namely, B. influenzæ, pneumococci and staphylococci (15 instances), and B. influenzæ, hemolytic streptococci and staphylococci (16 instances). There is little doubt that B. influenzæ was not identified in some instances in which it was present; when other microorganisms are very numerous its inconspicuous colonies may be overgrown even though the presence of pneumococci, streptococci or staphylococci tends to increase the size of its colonies. Moreover, it is not improbable that the microorganism may disappear from the bronchi. Comparison with observations made upon influenza suggests that multiple methods of examination might have demonstrated a much higher incidence of B. influenzæ. Throat cultures alone made during life demonstrated the presence of B. influenzæ in only 65.7 per cent of patients with acute influenza, whereas when cultures were made from the nose, throat and sputum, and a mouse was inoculated with sputum from each patient, B. influenzæ was found in every instance. After the acute stage of the disease had passed, the number of microorganisms diminished, and in many instances B. influenzæ disappeared from the upper air passages. In some of our autopsies B. influenzæ doubtless present during life has similarly disappeared before death due to pneumonia caused by pneumococci or streptococci. In view of these considerations it is not improbable that B. influenzæ demonstrated by a single culture in 80 per cent of instances has been constantly present.
Table XXVIII represents the incidence of pneumococci, hemolytic streptococci, staphylococci, and B. influenzæ in the bronchi, lungs and blood of those individuals with pneumonia in whom bacteriologic examination has been made at autopsy. The number of cultures made from the bronchi, lungs or blood of the heart is given in the second column of the table and in other columns are given the incidence in number and percentage of the microorganisms which have been mentioned.
| Table XXVIII | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| NO. OF CULTURES | PNEUMOCOCCI | HEMOLYTIC STREPTOCOCCI | STAPHYLOCOCCI | B. INFLUENZÆ | |||||
| NO. POSITIVE | PER CENT POSITIVE | NO. POSITIVE | PER CENT POSITIVE | NO. POSITIVE | PER CENT POSITIVE | NO. POSITIVE | PER CENT POSITIVE | ||
| Bronchus | 121 | 56 | 46.3 | 58 | 47.9 | 61 | 50.4 | 96 | 79.3 |
| Lung | 153 | 68 | 44.4 | 77 | 50.3 | 37 | 24.2 | 70 | 45.7 |
| Blood | 218 | 87 | 39.9 | 85 | 39.0 | 1 | 0.5 | 1 | 0.5 |
Cultures from the bronchus represent the bacteriology of the bronchitis of influenza. Infection of the lung following influenza doubtless occurs by way of the bronchi, so that the bacteria which cause pneumonia are present in the bronchi before they enter the lung tissue. The figures in Table XXVIII, similar to those previously cited, show the high incidence of B. influenzæ, and the occurrence of pneumococci, hemolytic streptococci and staphylococci each present in approximately half of all autopsies.
The figures in Table XXVIII are an index of the capacity of the microorganisms which enter the bronchi to invade the lungs and finally the blood. Pneumococci were present in the bronchi in 46.3 per cent of instances, in the lungs in only slightly less, and in approximately 40 per cent of autopsies they had penetrated into the blood. Hemolytic streptococci enter the bronchi with the same frequency and exhibit an equal ability to penetrate into the lungs and blood. Staphylococci enter the bronchi in half of these individuals, but penetrate into the lungs in only a fourth of the instances. They have entered the blood only once (Autopsy 263) in this instance in association with hemolytic streptococci. B. influenzæ has been present in the bronchi in approximately 80 per cent of autopsies. It is noteworthy that it has been found in the lung in little more than half this percentage of instances and has entered the blood only once (Autopsy 474), in this instance in association with hemolytic streptococci.
In a limited number of autopsies there was purulent bronchitis recognized by the presence of mucopurulent exudate in small bronchi. It has been stated that this group of cases is not sharply separable from other instances of bronchitis, because in some cases death has occurred before a purulent exudate has accumulated or in other instances a purulent exudate has been displaced by edema. Table XXIX shows the bacteriology of instances of purulent bronchitis:
| Table XXIX | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| NO. OF CULTURES | PNEUMOCOCCI | HEMOLYTIC STREPTOCOCCI | STAPHYLOCOCCI | B. INFLUENZÆ | |||||
| NO. POSITIVE | PER CENT POSITIVE | NO. POSITIVE | PER CENT POSITIVE | NO. POSITIVE | PER CENT POSITIVE | NO. POSITIVE | PER CENT POSITIVE | ||
| Bronchus | 66 | 33 | 50.0 | 32 | 48.5 | 36 | 54.5 | 53 | 80.3 |
The percentages of various bacteria with purulent bronchitis do not differ essentially from those obtained from all autopsies with pneumonia. B. influenzæ is found in approximately 80 per cent of autopsies. In 16 instances cultures were made from the purulent fluid contained in a small bronchus and the incidence of B. influenzæ (namely, 81.4 per cent) has not differed from that in the main bronchus. In 7 of 8 instances in which cultures were made, both from the right main bronchus and from the purulent fluid in a small bronchus, B. influenzæ was found in one or other in all but one autopsy (87.5 per cent); in this instance (Autopsy 472) respiratory disease began thirty-seven days before death and cultures from large and small bronchi at autopsy were overgrown by B. coli. Since observations upon influenza made during life have shown that B. influenzæ is constantly demonstrable when multiple methods are employed for its detection, the figures just cited give support to the suggestion that B. influenzæ is constantly present in the bronchi with the bronchitis of influenza.