TABLE 1.
Comparative histopathological progression patterns of murine inhalational plague infections in the major tissues affected
| Aerosol particle sizea | Tissueb | Progression of infection postchallengec
|
|||
|---|---|---|---|---|---|
| 24 h | 48 h | 72 h | 96 h | ||
| Small (1-3 μm) | Nasal mucosa | − | + | + | + |
| NALT | − | + | +++ | +++ | |
| Cervical node | − | + | + | +++d | |
| Mediastinal node | − | + | +++ | +++++ | |
| Lung | + | +++ | +++++ | +++++ | |
| Spleen | − | +++ | +++++ | +++++ | |
| Liver | − | + | +++ | +++++ | |
| Thymus | − | − | − | +++d | |
| Bone marrow | − | + | ++ | +++d | |
| Blood | − | + | +++ | +++++ | |
| Large (12 μm) | Nasal mucosa | − | +++ | +++++ | +++++ |
| NALT | − | +++ | +++++ | +++++ | |
| Cervical node | + | +++ | +++++ | +++++d | |
| Mediastinal node | − | − | − | ++ | |
| Lung | − | − | + | ++ | |
| Spleen | − | + | + | +++++ | |
| Liver | − | − | + | +++++ | |
| Thymus | − | − | + | +++++d | |
| Bone marrow | − | − | − | +++d | |
| Blood | − | − | + | + + + | |
The actual infectious doses delivered were 1.23 × 103 ± 0.3 × 103 CFU and 7.09 × 103 ± 0.45 × 103 CFU for the 1- and 12-μm-particle aerosols, respectively.
Stomach, intestinal, Peyer's patch, pharyngeal, esophageal, and kidney tissues were negative for Y. pestis until 96 h postinfection in both 1- and 12-μm-particle inhalational infections, correlating with bacteremia. Y. pestis was observed only in the capillaries of these organs. Inguinal and mesenteric lymph nodes displayed pathological changes, with Y. pestis and neutrophils present by 48 h postinfection, in the 1-μm-particle inhalational infection. Similar pathological changes were observed only at 96 h postinfection in the 12-μm-particle inhalational infection.
The severity of pathological sequelae was scored subjectively as follows: −, no sequelae; +, mild; +++, marked; and +++++, severe.
Tissue where activated/cleaved caspase-3 immunolabeling was observed. Caspase-3 immunolabeling was performed only at 96 h postinfection.