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Characteristics of Salmonella Bacteria

By Stephanie Chandler ; Updated August 14, 2017

Salmonella species are Gram-negative, flagellated facultatively anaerobic bacilli characterized by O, H, and Vi antigens. There are over 1800 known serovars which current classification considers to be separate speciesthree clinical forms of salmonellosis: (1) gastroenteritis, (2) septicemia, and (3) enteric fevers. This chapter focuses on the two extremes of the clinical spectrum—gastroenteritis and enteric feverSalmonellosis includes several syndromes (gastroenteritis, enteric fevers, septicemia, focal infections, and an asymptomatic carrier stateMost non-typhoidal salmonellae enter the body when contaminated food is ingested (Fig. 2). Person-to-person spread of salmonellae also occurs. To be fully pathogenic, salmonellae must possess a variety of attributes called virulence factors. These include (1) the ability to invade cells, (2) a complete lipopolysaccharide coat, (3) the ability to replicate intracellularly, and (4) possibly the elaboration of toxin(s). After ingestion, the organisms colonize the ileum and colon, invade the intestinal epithelium, and proliferate within the epithelium and lymphoid follicles. The mechanism by which salmonellae invade the epithelium is partially understood and involves an initial binding to specific receptors on the epithelial cell surface followed by invasion. Invasion occurs by the organism inducing the enterocyte membrane to undergo “ruffling” and thereby to stimulate pinocytosis of the organisms

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