FIG. 2.

Y. pestis with caf1A::IS1541 is fully virulent. (A) Mice were challenged by subcutaneous (s.c.) injection with the indicated numbers of CFU of Y. pestis CO92 (wild type) or CAC1 (caf1A::IS1541) to precipitate bubonic plague, and their survival was monitored. (B) Strains were inoculated intranasally (i.n.) into mice to precipitate pneumonic plague. (C) Y. pestis strains were inoculated intranasally, and lung tissue replication and dissemination of plague bacteria into the spleen were measured on three consecutive days. (D) Lung tissue from animals infected as described above for panel C was fixed, thin sectioned, stained with hematoxylin-eosin, and viewed by microscopy.