Pathogenicity of Salmonella enteritidis phage types 4, 8, and 23 in broiler chicks

Four hundred fifty day-old Hubbard broiler chicks were subdivided into 15 g roups of 30 chicks each. Six groups of chicks received 0.5 mi of broth cult ure containing 5 x 10(6) colony-forming units (CFU) of Salmonella enteritid is (SE) phage types (PTs) 4, 8, and 23 by crop gavage. Similarly, six other groups received 0.5 ml containing 5 x 10(8) CFU of SE. One group was inocu lated with 0.5 mi containing 5 x 10(6) CFU of Salmonella pullorum, and anot her group received 0.5 mi containing 5 x 108 CFU of S, pullorum. A group of 30 chicks were kept as uninoculated controls. Chicks were observed daily f or clinical signs and mortality. All birds were weighed at 7, 14, and 21 da ys postinoculation 21 (DPI). Four chicks were randomly selected from each t reatment group, euthanatized, and necropsied at 7 and 14 DPI. Gross lesions were recorded and selected tissues were collected for histopathology. The higher rates of illness and mortality were observed in chicks inoculated wi th 5 x 10(6) and 5 x 10(8) CFU of S. pullorum, followed by SE PT4 of human origin and SE PT4 of chicken origin. Moderate to high mortality was observe d in chicks inoculated with the higher dose of SE isolates that belonged to PT8 and one SE of PT23. Variable mortality was evident in groups inoculate d with the lower dose of salmonella. The most consistent gross and histopat hologic changes, including fibrinous pericarditis and perihepatitis, were s een in the dead birds from various treatment groups. The lower mean body we ights were present in all treatment groups compared with uninoculated contr ols. No illness or mortality was observed in uninoculated control groups.