STUDIES ON THE MECHANISM OF RECOVERY IN PNEUMONIA DUE TO FRIEDLANDER'S BACILLUS : I. THE PATHOGENESIS OF EXPERIMENTAL FRIEDLANDER'S BACILLUS PNEUMONIA

Experimental pneumonia due to Friedländer's bacillus was produced in white rats by the intrabronchial inoculation of the bacilli suspended in mucin. The pneumonia was lobar in type, was almost uniformly fatal, and simulated the acute form of the natural disease in human beings. The pathogenesis of the pneumonic lesion was studied by examination of microscopic sections of the lungs of animals killed at frequent intervals during the course of the infection. The histologic characteristics of the various stages of the pneumonia were essentially the same as those previously described in experimental pneumococcal (Type I) pneumonia except for the following differences: (1) In isolated areas of the lung in Friedländer's pneumonia many more bacteria were encountered in the alveoli than were ever noted in experimental pneumococcal pneumonia. (2) Abscess formation was common in the late stages of Friedländer's infection, whereas it was not noted in the pneumococcal lesion. (3) Organization of the alveolar exudate, rarely observed in experimental pneumococcal pneumonia, was a prominent feature of the pneumonia due to Friedländer's bacillus. The mechanism of spread of Friedländer's lesion appeared to be the same as that of pneumococcal pneumonia. Likewise there was noted the same phagocytosis of organisms in the lungs of even bacteremic animals dying of the infection.

ST. LOUIS ENCEPHALITIS : TRANSMISSION OF VIRUS TO CHICKENS BY INFECTED MITES DERMANYSSUS GALLINAE AND RESULTING VIREMIA AS SOURCE OF VIRUS FOR INFECTION OF MITES

Transmission of the virus of St. Louis encephalitis to normal chickens by the bite of infected mites (Dermanyssus gallinae) has been demonstrated. Both experimentally infected and naturally infected mites were shown to be capable of transferring the virus of St. Louis encephalitis to chickens by bite. Virus is present in the blood of such chickens in small amounts, so that demonstration of viremia was possible only by utilizing chorioallantoic passage in hens' eggs. However, there is sufficient virus present in the blood for uninfected chicken mites to acquire the virus by feeding on chickens in which viremia has resulted from previous bite of infected mites. Thus it has been shown that the arachnid vector Dermanyssus gallinae is capable of transmitting the virus of St. Louis encephalitis to normal chickens by bite and that such chickens can serve as a source of virus for uninfected mites.

Encephalitis in experimental Coxsackie B-3 infection

A study has been made of the vulnerability of various parts of the brain in experimental Coxsackie B-3 virus infection. The standard prototype Coxsackie B-3 virus and a stock of inbred albino mice have been used for this purpose. The sites of greatest susceptibility have been precisely defined by thorough examinations of the whole brain and it has been observed that in 7- to 12-day-old mice the lesions are confined to sensory centers.Furthermore, observations have been made upon the effects of various factors such as the age at the time of inoculation, the state of myelination in different parts of the brain, and the route of inoculation. The complete resistance of the cerebellum to damage in spite of multiplication of virus in this site is of considerable interest.In the past little attention has been paid to the anatomical distribution of the brain lesions caused by the Coxsackie group B virus. It would seem to be profitable to direct attention to the features of the experimental disease in view of our lack of basic information regarding many non-fatal illnesses which affect the brain.

The Role of Various Chemical Fractions of M. tuberculosis and Other Mycobacteria in the Production of Allergic Encephalomyelitis

A single dose of 1 mg. of wax D fractions of several different strains of human type M. tuberculosis when injected in water-in-oil emulsion together with 16 mg. of homologous brain caused a high percentage of guinea pigs to develop encephalitis. Wax D fractions of several strains of bovine type and one strain of avian type M. tuberculosis and of M. phlei were found ineffective in inducing encephalitis when injected in the same dose and under similar conditions, although M. phlei and delipidated bovine type M. tuberculosis Marmorek bacilli were effective. Cord factor (trehalose dimycolate) and crude wax C fractions from human type M. tuberculosis were ineffective. These results are discussed in relation to the suggestion that the encephalitogenic activity of mycobacteria is due to the presence of a peptide consisting of alanine, glutamic and diaminopimelic acids linked to a glycolipid.

The precise correspondence between the activity of a wide variety of bacillary fractions as encephalitogenic agents in causing an increase in serum antibody to ovalbumin, and in inducing severe corneal reactivity to ovalbumin gives further support to the hypothesis that the encephalitis is the result of an isoimmunization process, in which the mycobacteria increase the immune response to an antigenic constituent of the brain tissue.

Encephalitogenic bacillary fractions produce histological reactions at the injection site and in the draining lymph nodes characterized by the formation of large numbers of epithelioid cells. It is suggested that these cells play an essential rôle in the adjuvant response.

Discussion on experimental allergic encephalitis

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