Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Veterinary Pathology


Liver, spleen, and blood were studied by bacteriologic culture in 3-week-old turkeys given virulent or avirulent Escherichia coli intravenously (i.v.). Liver and spleen were examined by light and electron microscopy to determine sites of bacterial localization. Twenty minutes after inoculation, numbers of avirulent bacteria were reduced to 1/3,000 of their numbers at 2 minutes; numbers of virulent bacteria in blood were only slightly reduced. Both avirulent and virulent E. coli were present in macrophages of splenic reticular sheaths (ellipsoids) and hepatic sinusoids. In spleens, avirulent and virulent E. coli were present in similar numbers but in liver avirulent bacteria were present in greater numbers. This study indicates that virulent E. coli bacteria resist phagocytosis, particularly by hepatic macrophages;Clearance of virulent E. coli from blood and localization in tissue were studied in normal and passively immunized turkeys after i.v. inoculation. Passive immunization of turkeys was associated with large numbers of E. coli in liver as determined by culture and microscopic examination. In passively immunized poults, extracellular bacteria were covered by an electron-dense, fibrillo-granular coat and were commonly clumped in reticular sheaths and red pulp of spleen and sinusoids of liver. Persistence of large numbers of E. coli in blood and high mortality were associated with small numbers of E. coli in livers of normal poults. This study indicates that rapid clearance of virulent E. coli from blood requires antibody-dependent localization in liver;The acute pathologic changes of spleen and liver were studied in 3-week-old turkeys inoculated i.v. or intratracheally with virulent E. coli. Intratracheal inoculation resulted in low numbers of bacteria in blood for 3 to 5 days and only mild lesions in spleen and liver. Spleens of poults inoculated i.v. had necrosis and fibrinopurulent exudates in reticular sheaths, hyperemia of red pulp, and aggregates of thrombocytes in venous sinuses. Livers of birds killed in extremis were markedly hyperemic; centrolobular hepatocytes were vacuolated or necrotic. Small hepatic veins were commonly occluded by thrombocyte aggregates and fibrin. Bacteria were numerous in hepatic sinusoids and phagocytes. Phagosomes of hepatic macrophages frequently contained up to 10 normal appearing bacteria, whereas bacteria within heterophils showed degenerative changes ultrastructurally. This study indicates that liver may be an important site of bacterial colonization in turkeys with progressive E. coli bacteremia.



Digital Repository @ Iowa State University,

Copyright Owner

Lawrence Harry Arp



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124 pages