Infectious Disease Salmonellosis Term Paper

Infectious Disease Salmonellosis

Salmonellosis, named after pathologist Daniel S. Salmon who first isolated the organism from porcine intestine, was first described in 1880 and cultured in 1884 (Salmonellosis1 pp). Salmonellae are motile, gram-negative, rod-shaped bacteria of the family Enterobacteriaceae, and are common in the gastrointestinal tracts of mammals, reptiles, birds, and insects (Salmonellosis1 pp).

Salmonellae are potential enteric pathogens and a leading cause of bacterial food-borne illness (Salmonellosis1 pp).

With a single overarching species (Salmonella

choleraesuis) and over 2000 serotypes, salmonellae have been implicated in a spectrum of diseases, including enteric or typhoid fever (primarily

Salmonella typhi and Salmonella paratyphi), bacteremia, focal infections, and enterocolitis (typically Salmonella

typhimurium, Salmonella enteritidis, and Salmonella

heidelberg) (Salmonellosis1 pp).

Salmonellae is usually transmitted by consumption of contaminated foods, particularly beef, poultry, and eggs, although improperly prepared fruits, vegetable, dairy products, and shellfish have also been implicated, as well as human-to-human and animal-to-human transmission (Salmonellosis1 pp). The infectious dose varies among strains, however, a large inoculum is believed to be necessary to overcome stomach acidity and to compete with normal intestinal flora (Salmonellosis1 pp). Yet, lower infectious doses may be adequate to cause infection if these organisms are do-ingested with foods that rapidly transit the stomach, such as cheese and milk, or if antacids are used concomitantly, or if ingested by persons with impaired immune systems (Salmonellosis1 pp).

After ingestion, infection with salmonellae is characterized by attachment of the bacteria by fimbriae or pili to cells lining the intestinal lumen, then the bacteria are internalized by receptor-mediated endocytosis and transported within phagosomes to the lamina propria where they are released (Salmonellosis1 pp). Once there, salmonellae induce an influx of macrophages, typhoidal strains, or meutrophils, nontyphoidal strains, and although nontyphoid salmonellae generally precipitate a localized response, S typhi and other especially virulent strains invade deeper tissue via lymphatics and capillaries and elicit a major immune response (Salmonellosis1 pp).

In 1997, the estimated annual incidence of salmonellosis in the United States was 13.8 cases per 100,000 people, and the incidence is greatest among children and individuals who are institutionalized and nursing home residents (Salmonellosis1 pp). Salmonellae typically produces a self-limiting gastroenteritis, and dehydrated patients occasionally require hospitalization, however, death rarely occurs (Salmonellosis1 pp). Although uncommon, increased mortality rates are associated with extraintestinal complication of salmonellosis caused by seeding of bacteria to other organs, and include complications such as "endocarditis and arterial infections, cholecystitis, hepatic and splenic abscesses, urinary tract infections, pneumonia or empyema, meningitis, septic arthritis, and osteomyelitis" (Salmonellosis1 pp).

Salmonella infections generally produces one of three distinct syndromes, gastroenteritis, typhoid fever, or focal disease (Salmonellosis1 pp). Nontyphoidal salmonellae usually causes enterocolitis similar to that caused by other bacterial enteric pathogens (Salmonellosis1 pp). Nausea, vomiting, and diarrhea occur within six to forty-eight….....