The digestive tracts of humans and other animals contain many types of bacteria that aid in digestion, but some of these organisms may cause infections in humans. To determine if a person has a bacterial infection, doctors take stool samples and place them under conditions that allow bacteria to grow. If bacteria appear in the culture, doctors can look at the sample under a microscope and run chemical tests to identify the type of bacteria. The most common intestinal bacterial infections in humans include salmonella, Shigella, campylobacter and a specific strain of Escherichia coli (E. coli).
Salmonella, a bacterium commonly found in the intestines of birds, reptiles and some mammals, causes an infection called salmonellosis, a diarrheal illness, in humans. It is usually transmitted to humans when people handle or eat undercooked meat or other contaminated foods. People who handle the waste of infected animals can also contract this infection. Salmonella infections cause symptoms such as diarrhea, abdominal cramps and fever. Salmonellosis can lead to severe illness in infants, the elderly or people with weakened immune systems. Most people recover without medical treatment. Drinking fluids keeps the body from becoming dehydrated.
E. Coli (O157 Strain)
E. coli, a diverse group of bacteria, is usually harmless. In fact, it is normally present in the human intestines. However, some strains of these bacteria produce poisons, or toxins, that can cause harm to the intestines, kidneys and blood. E. coli O157 produces a toxin, the Shiga toxin that causes diarrheal sickness. Symptoms of an E. coli infection include stomach cramps, bloody diarrhea, vomiting and dehydration. While some infections are mild, others can be severe or life-threatening, especially in young children and the elderly. The best treatment is to remain hydrated while the disease runs its course.
Shigella causes a digestive tract infection called Shigellosis, which is usually transmitted to humans by the ingestion of contaminated food or drink. It produces toxins that attack the lining of the large intestine, resulting in swelling of the intestinal wall, ulcers and bloody diarrhea. Symptoms include abdominal cramps, severe diarrhea, vomiting, painful bowel movements, high fever and loss of appetite. Shigellosis occurs most often in young children. Doctors prescribe antibiotics, such as ampicillin, to treat this illness. Hydration is also an important part of treatment.
Campylobacter bacteria, which cause diarrheal illness, are the second most frequently reported cause of food-borne illness, according to the United States Department of Agriculture (USDA). These bacteria are found in the intestines of many domestic and wild animals and can be passed in their feces. People get campylobacter infections by consuming contaminated meat, especially chicken, contaminated water or unpasteurized milk. Symptoms include diarrhea, abdominal cramps and fever. Treatment includes ingesting fluids to counter dehydration. Although this infection usually clears up on its own, severe cases may require antibiotic treatment. People can prevent campylobacter infections by cooking meat thoroughly and drinking purified water and pasteurized milk.
- WebMD: Information and Resources: Stool Culture
- CDC: National Center for Zoonotic, Vector-Borne, and Enteric Diseases: Salmonellosis
- CDC: National Center for Zoonotic, Vector-Borne, and Enteric Diseases: Escherichia coli O157:H7
- USDA: Food Safety and Inspection Service: Fact Sheets: Campylobacter Questions and Answers
- KidsHealth: Infections: Shigella Infections
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