Changes in the rat placenta following inoculation with Salmonella dublin

The intraperitoneal inoculation of a suspension of Salmonella dublin (2.9 x 10(8) viable organisms) into thirteenth to fourteenth day pregnant rats produced reproductive failure. Rats were killed 6, 12, 18, 24, 48, 72, 96 and 120 hours after inoculation, and the pathogenesis of the lesions studied. The lesions progressed through four stages, starting with severe congestion of the placenta which developed rapidly and caused distortion of the labyrinth and sometimes resulted in hemorrhage onto the surface of the placental disc. Hemorrhage and necrosis in the decidua basalis produced placental detachment; subsequently, there developed an acute necrotizing inflammation of the placental sites which was followed by proliferation of granulation tissue. The initial lesions showed many similarities with those produced in rat and mouse placentas by endotoxins of gram-negative bacteria, indicating that the basic lesion produced in the placenta by endotoxin is slowing and stasis of the placental circulation.