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Bacteria of the genus Salmonella are highly adapted for growth in both humans and animals and cause a wide spectrum of disease. The growth of serotypes S. Typhi and S. Paratyphi is restricted to human hosts, in whom these organisms cause enteric (typhoid) fever. The remaining serotypes (nontyphoidal Salmonella, or NTS) can colonize the gastrointestinal tracts of a broad range of animals, including mammals, reptiles, birds, and insects. More than 200 serotypes are pathogenic to humans, in whom they often cause gastroenteritis and can be associated with localized infections and/or bacteremia. . | Chapter 146. Salmonellosis Bacteria of the genus Salmonella are highly adapted for growth in both humans and animals and cause a wide spectrum of disease. The growth of serotypes S. Typhi and S. Paratyphi is restricted to human hosts in whom these organisms cause enteric typhoid fever. The remaining serotypes nontyphoidal Salmonella or NTS can colonize the gastrointestinal tracts of a broad range of animals including mammals reptiles birds and insects. More than 200 serotypes are pathogenic to humans in whom they often cause gastroenteritis and can be associated with localized infections and or bacteremia. Etiology This large genus of gram-negative bacilli within the family Enterobacteriaceae consists of two species S. choleraesuis which contains six subspecies and S. bongori. S. choleraesuis subspecies I contains almost all the serotypes pathogenic for humans. Because the designation S. choleraesuis refers to both a species and a serotype the species designation S. enterica has been recommended and widely adopted. According to the current Salmonella nomenclature system the full taxonomic designation Salmonella enterica subspecies enterica serotype Typhimurium can be shortened to Salmonella serotype Typhimurium or simply Salmonella Typhimurium. Members of the seven Salmonella subspecies are classified into 2400 serotypes serovars according to the somatic O antigen lipopolysaccharide LPS cell-wall components the surface Vi antigen restricted to S. Typhi and S. Paratyphi C and the flagellar H antigen. For simplicity most Salmonella serotypes are named for the city where they were identified and the serotype is often used as the species designation. Salmonellae are gram negative non-spore forming facultatively anaerobic bacilli that measure 2-3 by 0.4-0.6 Pm. The initial identification of salmonellae in the clinical microbiology laboratory is based on growth characteristics. Salmonellae like other Enterobacteriaceae produce acid on glucose fermentation reduce nitrates
