FIG 3.

The effect of rifampin resistance marking on the virulence of C. perfringens strains in the necrotic enteritis disease induction model. The lesion scores of individual 24-day-old broiler chickens challenge with different C. perfringens strains are shown. The horizontal bars represent the average lesion score for each group, and the error bars represent the standard error for each group. Intestinal lesions in the small intestine (duodenum to ileum) were scored as previously reported: 0, no gross lesions; 1, thin or febrile walls; 2, focal necrosis or ulceration (one to five foci); 3, focal necrosis or ulceration (six to 15 foci); 4, focal necrosis or ulceration (16 or more foci); 5, patches of necrosis 2 to 3 cm long; and 6, diffuse necrosis typical of field cases. The results are from two separate trials. The strains tested are as follows: WER-NE36, EHE-NE18, and rifampin-resistant strains WER-NE36 and EHE-NE18, n = 20. A one-way ANOVA Kruskal-Wallis test with a Dunn's posttest showed a statistical difference between the rifampin-marked strains of WER-NE36 and EHE-NE18 from their wild-type forms, with P values of 0.001 for both strains examined.