Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology

First Advisor

Robert P. Ellis


Colibacillosis (CB) in livestock is an economically important disease caused by the bacterium Escherichia coli. It is estimated that nearly one third of all baby pigs born in South Dakota die prior to weaning, and one fourth of these deaths is believed to be caused by CB (62). Similarly, it has been stated that 6 to 20% of calves born alive die from this disease (3). The term colibacillosis encompasses a group of diseases caused by E. coli in neonatal and weaned animals and humans (3). The several different types of CB are due to the differences in tissue localization of the organism and the biological activity of the toxin. On this basis, the diseases caused by E. coli can be divided into four major groups: enterotoxic, enterotoxemic, local invasive and septicemic CB (42). Characteristics of enterotoxic CB include proliferation of E. coli in the lumen of the small intestine and production of enterotoxin. This causes the small intestine to secrete fluid and results in diarrhea. The organism does not invade the tissue (44, 61). In enterotoxemic CB, E. coli is localized in the small intestine and produces a toxin which is absorbed and acts elsewhere. An example of this is edema disease of swine (18). Invasion and destruction of intestinal epithelium by E. coli are characteristics of locally invasive CB. The organisms that produce this syndrome are not enterotoxigenic, and the mechanisms of invasion are unknown. The host responds with inflammation and ulceration of the intestine, dysentery, and fever (42). In septicemic CR, bacteremia is present with extraintestinal localization of the organism. There is endotoxin mediated damage to the host, and diarrhea may or may not be present (42). Enteropathogenic E. coli produce two types of enterotoxin. One is a heat labile toxin (LT), and the other is heat stable (ST). The LT has a high molecular weight, is nondialyzable; antigenic, and its action on the host is delayed and prolonged (11, 27, 35). It is similar to the enterotoxin produced by Vibrio cholerae (25). The effects of ST are rapid in onset and of short duration. It has a low molecular weight, is stable when heated 30 minutes at 100 C, and it is dialyzable and nonantigenic (28, 35, 53). The research reported herein is concerned with enterotoxigenic E. coli (EEC) infections and the ST produced by the organism. Purification and concentration of the ST were the main objectives. If the enterotoxins produced by EEC could be purified and characterized, the pathogenesis of the enterotoxic CB could be more fully understood. Toxin purification might also result in faster and easier tests for the diagnosis of the disease.

Library of Congress Subject Headings

Escherichia coli infections




South Dakota State University

Included in

Microbiology Commons