salmonella

Salmonella is a genus of Gram-negative, rod-shaped, non-spore-forming bacteria in the family Enterobacteriaceae. The genus comprises two species, Salmonella enterica and Salmonella bongori, with S. enterica responsible for most human disease. S. enterica is further divided into numerous serovars, such as Typhimurium, Enteritidis, Typhi and Paratyphi.

Most human illness is caused by non-typhoidal Salmonella, which is usually acquired through ingestion of contaminated food or water. After an incubation of about 6 to 72 hours, illness typically presents with diarrhea, abdominal cramps, nausea and sometimes fever. In healthy adults it is usually self-limited to several days. Typhoidal Salmonella, including S. Typhi and S. Paratyphi, causes typhoid fever, a systemic illness with prolonged fever, abdominal pain and hepatosplenomegaly; transmission is human-restricted, and chronic carriers may shed organisms for years.

Diagnosis is by stool culture for gastroenteritis; blood cultures may be used for typhoid or invasive disease. Treatment is mainly supportive; antibiotics are reserved for severe disease, high-risk patients, or invasive infection, and must consider local resistance patterns. Multidrug-resistant Salmonella and emerging resistance to fluoroquinolones and third-generation cephalosporins complicate therapy.

Prevention focuses on proper food handling, thorough cooking of poultry and eggs, pasteurization of dairy products, safe water, and good hand hygiene. Typhoid vaccines (oral Ty21a and injectable Vi polysaccharide) provide protection against S. Typhi and are recommended for travelers to high-risk areas; no broad vaccine prevents non-typhoidal salmonellosis.

Epidemiology: Salmonella is a leading cause of bacterial foodborne illness worldwide, with outbreaks linked to poultry, eggs, dairy, and fresh produce. Animal reservoirs include poultry, cattle, pigs, and reptiles; asymptomatic carriers can maintain transmission.