Salmonella is the common name for a group of bacteria that causes gastrointestinal illness. It is named after the scientist who discovered them, Salmon. This group of bacteria has been known to infect humans for over 100 years. The most common species that infects humans by contaminating food is Salmonella typhimurium and Salmonella enteriditis.
The Bacterium
Salmonella species, of which over 1000 strains exist, are flagellated, gram-negative bacteria. Systemic disease is caused by Salmonella typhi (typhoid fever), but the other strains cause food-borne or water-borne gastroenteritis. The bacteria invade the cells of the intestinal epithelium, producing lesions and inflammation. This process leads to excess drainage and erosion in the intestines. An enlarged spleen, liver involvement, and gall bladder infection can also occur with some strains.
Salmonella Infection
Salmonella infects approximately 40,000 people in the United States each year. The actual number of infections is likely much higher because mild cases do not get reported. Salmonella infection, known as salmonellosis, usually results in diarrhea, fever, and abdominal cramping 12 to 72 hours after ingestion. The illness, and the symptoms, usually last for a week or less. Most people recover without treatment or medication, but severe infections may require hospitalization for rehydration of lost fluids and possibly antibiotic therapy. The most at-risk individuals are the young, the elderly, those with chronic disease, and immunosuppressed individuals. It is more common in the Summer season.
It may take months for bowel habits to return to normal after food poisoning. Also, some strains of the bacterium have become resistant to antibiotic treatment. The passage of the bacteria from the intestines to the blood stream may result in death. Approximately 400 people die each year from salmonellosis. Immediate diagnosis increases the odds of appropriate treatment.
Testing for the Illness
A positive diagnosis of salmonella infection is usually accomplished by culturing the bacterium from a stool sample. Further DNA analysis then determines the serotype and can be used to track outbreaks and determine the source of the infection. It is important that the public health department be notified of salmonellosis cases, even mild ones, in order to confirm the source and serotype. The full information about an outbreak can lead to preventing further infections and deaths.
Protect against Salmonella Poisoning
Salmonella can be present in undercooked eggs, meat, and fish. It can contaminate other foods that come into contact with the raw or undercooked eggs, meat, or fish or if foodstuffs come into contact with contaminated feces. All utensils and surfaces should be washed with warm water and mild soap, including the hands, when cooking or preparing these foods. Fruits and vegetables should be washed prior to consumption. Salmonella has also been known to be carried by reptiles and birds. Pets should be handled safely according to CDC recommendations.
Additional information provided by:
Cotran, Kumar, and Collins. Robbins Pathologic Basis of Disease, 6th ed. Saunders.
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