Table: Microorganisms That Cause Gastroenteritis - Merck Manuals Consumer Version

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Microorganisms That Cause Gastroenteritis

Microorganisms That Cause Gastroenteritis

Microorganism	Common Sources	Symptoms	Antimicrobial Use
Astrovirus	Epidemic and often seasonal	Milder watery diarrhea Vomiting and fever Symptoms begin 3 to 4 days after infection Usually lasts 2 to 7 days Similar to rotavirus	Antibiotics and antiviral drugs are not given.
Campylobacter	Eating contaminated meat (especially undercooked poultry) Drinking contaminated water or unpasteurized milk	Often bloody, sometimes watery diarrhea lasting 1 day to a week or more	Antibiotics given in the early stages of illness may shorten the duration of symptoms (for example, azithromycin or ciprofloxacin).
Clostridium difficile	Usually due to bacterial overgrowth in people who have been taking antibiotics	Diarrhea	Antibiotic that caused the illness is stopped. Vancomycin or fidaxomicin is given by mouth. Metronidazole may be given to people who cannot tolerate vancomycin and fidaxomicin.
Cryptosporidium	Drinking contaminated water Person-to-person contact Recreational water exposure People with impaired immune systems are particularly susceptible	Watery diarrhea, crampy abdominal pain, nausea, fatigue, and vomiting Usually lasts about 2 weeks	Antiparasitic drugs are sometimes given (for example, nitazoxanide).
Entamoeba histolytica	Eating or drinking contaminated food or water	Bloody diarrhea, abdominal pain, weight loss lasting 1 to 3 weeks Can cause infection in liver and other organs	Antiparasitic drugs are given (for example, metronidazole, iodoquinol, or paromomycin).
Enterohemorrhagic Escherichia coli (most commonly E. coli O157:H7―see Hemorrhagic Colitis)	Eating undercooked ground beef or drinking unpasteurized milk or juice Swimming in contaminated pools Person-to-person contact Touching infected animals and then putting fingers in the mouth	Sudden abdominal cramps, watery diarrhea that usually becomes bloody within 1 to 3 days, and hemolytic-uremic syndrome in about 5% of people	Antibiotics are not given because they increase the risk of developing hemolytic-uremic syndromehemolytic-uremic syndrome.
Enterotoxigenic Escherichia coli (causes traveler’s diarrhea)	Eating or drinking contaminated food or water	Frequent watery diarrhea Usually lasts 3 to 5 days	Antibiotics (for example, ciprofloxacin or levofloxacin) may help shorten duration of illness. Azithromycin is given to children.
Giardia	Drinking contaminated water Person-to-person contact, particularly in day care centers	Diarrhea, nausea, and loss of appetite More long-term illness (lasting several days to several weeks) may occur, with greasy stools, abdominal bloating, gas, fatigue, and weight loss	Antiparasitic drugs are given (for example, metronidazole or nitazoxanide).
Intestinal adenovirus	Epidemic and often seasonal	Frequent watery diarrhea lasts 1 to 2 weeks Mild vomiting begins 1 to 2 days after diarrhea Fever affects 50% of people Symptoms begin 3 to 10 days after infection Usually lasts 10 days or more	Antibiotics and antiviral drugs are not given.
Norovirus	Epidemic and often seasonal	Frequent watery diarrhea Vomiting, especially in children Stomach cramps, headache, and aches and pains Fever higher than 102° F (about 39°C) occurs in about 30% of people Diarrhea usually affects adults Symptoms begin 1 to 2 days after infection Usually lasts 2 to 7 days	Antibiotics and antiviral drugs are not given.
Rotavirus	Epidemic and often seasonal	Frequent watery diarrhea Vomiting and fever higher than 102° F (about 39°C) Symptoms begin 1 to 3 days after infection May last 5 to 7 days	Antibiotics and antiviral drugs are not given. Vaccines are available for infants.
Salmonella	Eating contaminated food Contact with reptiles (for instance, iguanas, snakes, and turtles), birds, or amphibians (for instance, frogs and salamanders)	High fever, exhaustion, abdominal cramps, nausea, vomiting, diarrhea that may or may not be bloody Symptoms usually last 3 to 7 days	Antibiotics usually are not given.
Shigella	Person-to-person contact, especially in day care centers	May be mild or severe In mild cases, watery, loose stools In severe cases, high fever, exhaustion, severe abdominal cramps, painful passage of stool containing blood and mucus Symptoms usually last about a week without treatment	Antibiotics shorten the duration of the illness and decrease chance of spread to another person (for example, ciprofloxacin or trimethoprim-sulfamethoxazole).
Staphylococcus aureus (see also Staphylococcal Food Poisoning) Bacillus cereus Clostridium perfringens	Eating food contaminated by toxins produced by bacteria	Severe nausea, vomiting, and diarrhea Symptoms begin within 12 hours after eating contaminated food and lessen within 36 hours	Antibiotics are not given.
Vibrio cholerae	Eating or drinking contaminated food or water	Painless, watery diarrhea and vomiting Can lead to massive fluid loss and shock	Antibiotics are given (for example, ciprofloxacin or doxycycline).
Other types of Vibrio	Shellfish	Watery diarrhea, often with little nausea or vomiting	Antibiotics are given (for example, ciprofloxacin, doxycycline, or trimethoprim/sulfamethoxazole).