Edema disease as a model for systemic disease induced by Shiga toxin-producing E-coli

Edema disease (ED) is a naturally occurring disease of weaned pigs caused b y host adapted strains of E. coli that produce Shiga toxin (STEC). We deter mined the temporal and quantitative relationships between intestinal coloni zation by STEC, levels of Shiga toxin (Stx2e) in the gut, in the blood, and clinical manifestations of ED. Bacterial colonization (10(8) CFU/cm ileum) was highest 4 days post inoculation (pi) in animals that did not develop c linical disease and 6 days pi in animals with clinical signs of ED. The mea n time for the development of clinical signs of ED was 6 days pi (range 4-1 0). Average peak titers of Stx2e in the ileum were 1:16,384 in asymptomatic animals and 1:32,768 in clinical animals. Titers of Stx2e in the feces ref lected the toxin titers in the ileum but were lower. Intestinal titers of S tx2e and the density of bacterial colonization were predictive of clinical ED for a group of animals but not for individuals. Approximately 50% of the pigs that had Stx2e titers of greater than or equal to 1 :4096 and a bacte rial density of greater than or equal to 10(6) CFU/cm in their ileum. had c linical ED. Pigs that had intestinal Stx2e titers <1: 4096 were asymptomati c. Stx2e was detected in the red cell fraction of blood from some of the pi gs with clinical ED and in some that were asymptomatic. Stx2e was not detec ted in the serum of any animals. ED may be a useful model for predicting th e temporal and quantitative relationships between bacterial colonization, S tx levels in the gut and blood and systemic disease for STEC in other speci es.