Salmonella bacteria are one of the most common causes of foodborne illness around the world, according to the World Health Organization. In the United States alone, 40,000 cases are reported to the Centers for Disease Control and Prevention each year, although many more go unrecognized. In 2008 and 2009, salmonella infections were the subject of a number of media reports when contaminated peanut butter was distributed to schools, nursing homes and snack food manufacturers. There are more than 2,500 types of salmonella bacteria.
Gastroenteritis
Most salmonella subspecies, including the two most common variants--Salmonella enteridis and Salmonella typhimurium, produce "salmonellosis" which is a mild, self-limited gastroenteritis. Symptoms including fever, stomach cramps, nausea, vomiting and diarrhea typically appear within 12 to 72 hours of ingestion and resolve within four to seven days. Young children, the elderly and people with medical problems may require hospitalization for dehydration. Antibiotics are required in less than 2 percent of cases.
Bloodstream and Metastatic Infections
In rare cases, salmonella bacteria may escape the intestine to enter the bloodstream. Signs and symptoms of sepsis include abnormally high or low body temperature; abnormally high or low heart rate; abnormally high or low respiratory rate; shaking chills; and altered mental status. In the United States, salmonella sepsis is not generally fatal and can usually be managed with antibiotics.
In some cases, salmonella bacteria in the bloodstream are able to spread (metastasize) to other areas of the body such as the valves and lining of the heart (endocarditis), other soft tissues including the brain, and bone. These complications are uncommon in healthy adults. Almost all cases occur in immunocompromised people (AIDS, cancer and sickle cell anemia) or people with multiple medical problems.
Autoimmune Disease
After salmonella exposure, the immune system makes antibodies to the bacteria. Unfortunately, salmonella bacteria resemble a cell surface marker present in many people. The result is an autoimmune disease cause Reiter's syndrome which produces chronic joint pain (arthritis), eye irritation (conjunctivitis with or without iritis), and problems with urination (urethritis). In a 2001 study presented in the journal "Clinics in Infectious Disease," nearly one-third of people who were infected with Salmonella enteridis, one of the most common salmonella species, developed arthritis which persisted for up to six months and nearly 50 percent reported recurrence after the initial episode resolved.
Typhoid Fever
Typhoid, or enteric, fever is caused by infection with Salmonella typhi and is uncommon in developed countries. Symptoms usually develop one to three weeks after exposure and include characteristic high fever; weakness, lethargy or muscle pain; headache; loss of appetite; and diarrhea or constipation. In severe cases, symptoms of altered mental status and meningitis (fever, stiff neck, seizures) have been reported. Mortality approaches 10 percent without treatment and may be reduced to less than 1 percent with appropriate antibiotics.
References
- World Health Organization: Drug Resistant Salmonella
- Centers for Disease Control and Prevention: Salmonella
- "Clinics in Infectious Disease;" Reactive Arthritis and Reiter's Syndrome Following an Outbreak of Gastroenteritis Caused by Salmonella Enteritidis; M.S. Dworkin, P.C. Shoemaker, M.J. Goldoft, J.M. Kobayashi; Oct. 1, 2001
