A model of pneumonia due to Pseudomonas aeruginosa was produced in hamsters by an intratracheal bolus instillation of microorganisms. Sequential lung changes from 4 hr through 11 days were studied by morphologic and microbiologic methods. Hamsters inoculated with > 106 pseudomonads survived but consistently had histologic evidence of mild bronchopneumonia 24 hr postinoculation, whereas a severe bronchopneumonia and a 100% mortality were elicited with a 108 inoculum of organisms in 0.5 ml phosphate-buffered saline (PBS). An inoculum of 107 pseudomonads/0.5 ml PBS was then used to define the changes in the bacterial population in Pseudomonas pneumonia and to obtain serial histopathologic observations. Quantitative lung cultures obtained within 1 hr postinoculation demonstrated a mean of 106 colony forming units per lung, and none of the hamsters were bacteremic. However, by 24 hr bacterial counts had increased and all animals were bacteremic. Bacterial proliferation continued through 48 hr; however, the number of bacteremic animals had decreased. By 72 hr, bacterial counts had decreased with total Pseudmonas clearance noted by 120 hr. A striking polymorphonuclear leukocyte-rich alveolar exudate was present by 12 hr. Pseudomonas "vasculitis" was evident by 24 hr. The evolution of this vascular lesion correlated with the bacteremic state of the hamsters. By 11 days, resolution of the pneumonic process was seen. The macroscopic and microscopic features of this hamster model of Pseudomonas pneumonia are very similar to those reported in infected patients.
ASJC Scopus subject areas
- Pathology and Forensic Medicine
- Molecular Biology
- Clinical Biochemistry