Clinical Manifestations
Salmonellosis ranges clinically from the common Salmonella gastroenteritis (diarrhea, abdominal cramps, and fever) to enteric fevers (including typhoid fever) which are life-threatening febrile systemic illness requiring prompt antibiotic therapy. Focal infections and an asymptomatic carrier state occur. The most common form of salmonellosis is a self-limited, uncomplicated gastroenteritis.
Structure, Classification, and Antigenic Types
Salmonella species are Gram-negative, flagellated facultative anaerobic bacilli characterized by O, H, and Vi antigens. There are over 1800 known serovars which current classification considers to be separate species.
Pathogenesis
Pathogenic salmonellae ingested in food1 survive passage through the gastric acid barrier2 and invade the mucosa of the small and large intestine3 and produce toxins4. Invasion of epithelial cells stimulates the release of proinflammatory cytokines5 which induce an inflammatory reaction6. The acute inflammatory response causes diarrhea and may lead to ulceration and destruction of the mucosa7. The bacteria can disseminate from the intestines to cause systemic disease.
Host Defenses
Both nonspecific and specific host defenses are active. Non-specific defenses consist of gastric acidity1, intestinal mucus2, intestinal motility (peristalsis)3, lactoferrin4, and lysozyme5.
Specific defenses consist of mucosal and systemic antibodies and genetic resistance to invasion. Various factors affect susceptibility.
Epidemiology
Non-typhoidal salmonellosis is a worldwide disease of humans and animals. Animals are the main reservoir, and the disease is usually food borne, although it can be spread from person to person. The salmonellae that cause Typhoid fever and other enteric fevers spread mainly from person-to-person viaCopyright © 1996
The University of Texas Medical Branch at Galveston