Plague bacillus: survival within host phagocytes.

Pasteurella pestis within nelutrophiles and macrophages removed from the peritoneal cavity of guinea pigs dutring experimental plague were shown to be viable by direct microscopic observation of the infected phagocytes incubating in sutitable bacteriologic media. The time-honored hypothesis that the major determinanit of the virulence of the plague bacillius is its ability to resist ingestion by phagocytes mutst be reevaluated.