Role of fimbriae as antigens and intestinal colonization factors of Salmonella serovars

Abstract

The two most important human disease syndromes caused by Salmonella serovars are typhoid fever and enterocolitis. Typhoid fever is a systemic infection caused by Salmonella serovars which are strictly adapted to humans or higher primates, including Salmonella enterica serovars Typhi and paratyphi A, B, and C. Human enterocolitis is an infection localized to the intestine and mesenteric lymph nodes which can be caused by any of more than 2000 Salmonella serovars, however, S. enterica serovars Typhimurium and Enteritidis together account for approximately 50% of cases in the USA. The animal model most frequently used to study Salmonella pathogenesis is the typhoid fever-like disease caused by serovar Typhimurium in mice. The pathology in the intestine of mice infected with serovar Typhimurium is characterized by a predominantly mononuclear leukocyte infiltrate, as well as edematous villi which become shortened in height [1]. Capillary thrombosis, hemorrhage, and ulcerations may be present at areas of Peyer's patches. The intestinal pathology caused by serovar Typhimurium in mice is similar to that observed in typhoid fever patients. That is, intestinal biopsies taken from volunteers infected with serovar Typhi or from typhoid fever patients reveal a predominantly mononuclear leukocyte infiltrate [2,3]. Furthermore, colonization of human Peyer's patches by serovar Typhi commonly produces capillary thrombosis, which can result in hemorrhage, necrosis and ulceration [4]. In humans, these lesions can progress to intestinal perforation, a potentially fatal complication which usually occurs in the third week of infection [4]. In contrast, rapid bacterial multiplication in the liver and other internal organs of mice causes death within 6–10 days post serovar Typhimurium infection, while intestinal perforation has not been reported in this model. Since intestinal perforation is an important cause of death during typhoid fever [4], it is likely that …