Virulence of different Pseudomonas species in a burned mouse model: tissue colonization by Pseudomonas cepacia

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Abstract
The virulence of P. aeruginosa and other pseudomonads was examined in a burned mouse model. P. aeruginosa M-2 was highly virulent causing 100% mortality by 38 h with an injection of 102 CFU [colony-forming units] s.c. or i.p. S.c. injection of 102 CFU revealed rapid multiplication of the bacteria at the burn wound with 108 CFU/g detectable in the burned skin by 28 h postinjection, 105 CFU/g of liver and 103 CFU/ml of blood. Non-P. aeruginosa clinical isolates were markedly less virulent; an injection of .gtoreq. 107 CFU caused .ltoreq.60% lethality. P. cepacia SMH colonized the burned skin of thermally injured mice, persisting at levels of 107-108 CFU/g of burned skin after an initial injection of 105 CFU. P. cepacia persisted in the burn wound for at least 3 wk. No organ invasion was detectable throughout this period. Studies with an additional clinical isolate of P. cepacia yielded similar results. An injection of a 102 CFU dose revealed that the level of persistence is dose dependent. Evidently, the tenacious persistence of P. cepacia in the burn wound may provide a model for the study of persistent colonization and infection in a compromised host.