Abstract
Summary and Conclusions
An agent pathogenic for guinea pigs has been isolated. The organisms appeared as small pleomorphic bacillary forms, staining red by the Machiavello method and gram negative. They were larger than the known rickettsia, as well as P. tularensis and Brucella, and were immunologically distinct from them. They grew fairly well in the yolk sac of the fertile hen's egg but were not cultivated on artificial media. The host range was limited to the guinea pig except when enormous doses were given.
After a short incubation period, peritonitis was produced in the guinea pig, for which the agent was highly virulent, and a specific immunity resulted in recovered animals. The inflammatory reaction in the tissues was characterized chiefly by the presence of mononuclear cells. The organism appeared predominantly intracytoplasmic in impression smears of the spleen.
The origin of the organism is in doubt. It has not been possible to identify it with any known group of pathogenic agents, but at present it may be termed “rickettsia-like” for descriptive purposes.
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