Written by Ada’s Medical Knowledge Team
What is bacterial gastroenteritis?
Bacterial gastroenteritis is a type of gastroenteritis – a common condition sometimes called stomach flu or food poisoning.
Gastroenteritis is the result of irritation and inflammation in the stomach and intestines. It can have many different possible causes, including infection with a virus, such as rotavirus (see viral gastroenteritis), bacteria or parasites. When caused by bacteria, it is called bacterial gastroenteritis.
The condition can affect adults and children. Symptoms of bacterial gastroenteritis can range from mild to severe and vary depending on the type of bacteria that have caused the infection. The main symptom is usually diarrhea. Other symptoms may include: 1 2 3 4
- Abdominal (belly) pain or cramps
- Loss of appetite
- Nausea and vomiting
- In severe cases, blood in the stool (feces); if blood is present, medical attention should be sought as a matter of urgency.
Bacterial stomach flu can be caused by a number of different types of bacteria, which are most often spread through contaminated food and beverages. Depending on the source of infection, a large group of people may develop symptoms of bacterial gastroenteritis, or food poisoning, at the same time. 2 3 5
While it can be very unpleasant, most cases of bacterial gastroenteritis can be treated at home, and clear up within a few days without causing complications. 1 6 Treatment for bacterial gastroenteritis typically involves: ref1 2 3 4 5
- Resting at home
- Drinking plenty of fluids to avoid dehydration
- When necessary, taking medication to relieve nausea and diarrhea.
Antibiotics are generally only recommended for more severe types of bacterial gastroenteritis.
Symptoms of bacterial gastroenteritis
- Abdominal (belly) discomfort, pain or cramps
- Loss of appetite
- Nausea and vomiting
- Fever and chills
- Body aches
- Feeling of weakness
- In severe cases, blood in the stool (feces).
Symptoms may be mild or more severe, and vary depending on the type of bacteria. If you think that you might have stomach flu, you can try using the Ada app to find out more about your symptoms.
If symptoms are severe or do not improve within 2-3 days, it is important to contact a doctor without delay. Furthermore, medical attention should be sought immediately if:
- There are any indications of severe dehydration, such as passing little to no urine or dizziness that does not go away
- There is blood, pus or a black color in the diarrhea
- There is constant vomiting that makes it impossible to keep down fluids
- There is very intense abdominal pain
- There is a fever over 38 degrees Celsius (101 F), in adults or children
In addition, a doctor should be contacted urgently if the affected person:
- Is pregnant
- Is a very young child
- Is an elderly person
- Has a weakened immune system
- Has a chronic condition such as inflammatory bowel disease or diabetes.
Causes of bacterial gastroenteritis
- Escherichia coli (E.coli)
- Clostridium difficile.
- Unhygienic food preparation, e.g. a cook not washing their hands after going to the toilet, or using the same cutting boards for both meat and salads
- Raw or undercooked meat, eggs and fish
- Unpasteurized dairy and juices
- Inadequately-treated drinking water.
Bacterial food poisoning can also be contracted from food that is not stored properly, e.g. poor refrigeration that leads to food spoiling, as well as from raw fruits and vegetables that are not thoroughly washed in clean water. Contact with reptiles, birds and amphibians can also be a route of transmission for Salmonella bacteria.
Bacterial gastroenteritis is a common cause of traveler’s diarrhea, a condition which frequently affects overseas travelers, particularly in developing countries. It is often the result of inadequate food hygiene at local restaurants and food outlets. 7 For more information on traveler’s diarrhea, including when to see a doctor, see the FAQs section.
Bacterial gastroenteritis caused by exotoxins
Some cases of bacterial gastroenteritis are not caused by bacteria themselves, but instead by toxins that they release. The harmful byproducts of certain types of bacteria can contaminate food, causing a type of food poisoning when ingested. These byproducts are called exotoxins, and they usually cause symptoms within 12 hours of consuming the contaminated food. This type of gastroenteritis typically clears up within 36 hours. 8
Diagnosis of bacterial gastroenteritis
When symptoms are mild, a diagnosis of bacterial gastroenteritis can often be made without seeing a doctor, and the condition can be treated at home. 1 However, if there is any uncertainty or concern over the condition, or symptoms are severe, seeing a doctor is very important.
A doctor will take the person’s medical history and perform a physical examination, taking care to rule out other gastrointestinal conditions such as gastritis. In most cases, it will not be necessary to order tests to confirm the diagnosis of gastroenteritis. However, in cases that are severe or long-lasting, a doctor may request blood tests and/or stool tests. 1 2 3
Bacterial gastroenteritis treatment
Most cases of bacterial gastroenteritis clear up without specific medical treatment. As long as symptoms are not severe and there are no signs of dehydration, a person can generally treat bacterial gastroenteritis in an adult or child at home.
- Bed rest
- Consuming plenty of fluids in the form of water or oral rehydration drinks; at the very least, small sips should be taken between being sick or having bowel movements
- Eating light meals when the appetite returns; plain foods like bread and rice may be helpful
- Taking an antidiarrheal medication, e.g. loperamide, only when necessary and there is no fever, and no blood or mucus is present in the stool
- Taking antiemetic (anti-nausea) medicine for nausea and vomiting, when necessary.
Good to know: In the past, the BRAT (Bananas, Rice, Applesauce, Toast) diet was often recommended for an upset stomach, e.g. one caused by gastroenteritis. However, because this bland diet lacks important nutrients like protein, it is now recommended that a regular, balanced diet be resumed as soon as possible for the person. 10
If a person is unable to keep any fluids down or shows signs of dehydration (see below), they may need to be treated with an IV drip at a hospital.
Antibiotics for bacterial gastroenteritis
In mild cases of bacterial gastroenteritis, antibiotics are typically not considered necessary and will not be prescribed. Antibiotic medication is generally only recommended in severe or persistent cases of bacterial food poisoning, in some cases of traveler’s diarrhea, in infections with C. difficile and in cases where the person has a weakened immune system or is otherwise at risk of complications. The type of antibiotics needed will depend on the specific type of bacteria, which may need to be determined with laboratory tests. 2 11
Complications of bacterial gastroenteritis
Generally, a bout of bacterial gastroenteritis clears up completely, without causing any complications. In a few cases, there may be complications. The risk of developing complications from bacterial gastroenteritis is highest in very young children, elderly people, and people who have a chronic condition such as diabetes, or who have a weakened immune system. 1 6 3
Dehydration may present with the following signs and symptoms in adults: 12
- Urinating less and dark colored urine
- Dry mouth
- Muscle cramps
- Eyes appear sunken in the head
Additional signs which may help to identify dehydration in children include: 12
- Drowsiness or irritability
- Increased heart rate
- Fewer wet nappies
- No tears when crying.
If signs and symptoms of dehydration do not go away with the replacement of lost fluids, or if a person is unable to keep fluids down, a doctor should be seen immediately. Dehydration can be extremely serious.
- Reduced effectiveness of medications, e.g. birth control pills or diabetes medicine
- Temporary intolerance to lactose, the sugar in cow’s milk
- Irritable bowel syndrome
- Reactive inflammation in other parts of the body, causing conditions like reactive arthritis
- The infection spreading to other parts of the body, e.g. the bones, joints, gallbladder, or the tissue around the brain and spinal cord (meninges)
- Persistent diarrhea
- Hemolytic uremic syndrome, a serious condition characterized by anemia and kidney failure
- Bleeding in the gastrointestinal tract
- Guillain-Barre syndrome, a serious condition in which the body’s immune system mistakenly attacks the nerves. 13
Prevention of bacterial gastroenteritis
Good personal hygiene and food preparation hygiene, as well as safe food storage and the use of water only from clean, adequately-treated sources, can help to reduce the risk of developing bacterial gastroenteritis.
- Always wash your hands well with soap and water, or use an alcohol-based hand sanitizer, after using the toilet
- Always wash your hands well before preparing food, and after handling any raw meat or fish
- Wash fruit and vegetables in clean water before using them
- Use different chopping boards for meat and vegetables, and clean them thoroughly with a disinfectant after use
- Regularly clean kitchen work surfaces with a disinfectant
- Cook all meat and fish well
- Store food in clean containers at appropriate temperatures; throw out anything that seems to have spoiled
- When traveling to other countries, drink only bottled water or water that has been boiled for at least 10 minutes; and only eat food that has been well cooked and fruit that can be peeled. 9
Bacterial gastroenteritis is contagious and can be spread easily. For this reason, it is important for people who have bacterial gastroenteritis to take precautions to avoid passing it on to other people. If you have bacterial gastroenteritis, in addition to the actions above, doing the following can help to prevent the spread of the infection: 1 6 4 9
- Clean the toilet and bathroom thoroughly with disinfectant on a daily basis
- Avoid sharing cutlery, towels, clothing and linen; also wash your items separately in hot water, with bleach if possible
- Avoid preparing food for other people for at least two days after the vomiting or diarrhea has cleared up
- Stay off work or school, if possible, until at least two days after the vomiting or diarrhea has cleared up
- Avoid swimming for two weeks after the vomiting or diarrhea has cleared up.
Bacterial gastroenteritis FAQs
Q: Is bacterial gastroenteritis contagious?
A: Yes, bacterial gastroenteritis is contagious, which means that it can be spread directly from person to person. However, it is most often spread via contaminated food and water. Practicing good hygiene, such as washing one’s hands with soap and water or using an alcohol-based hand sanitizer after going to the toilet and before eating, can help to reduce the risk of developing bacterial gastroenteritis. 1 2
Q: How long does bacterial gastroenteritis last?
A: The duration of a bout of bacterial gastroenteritis is usually a couple of days to a week, though some types of bacteria cause symptoms that last for just a day, and others cause symptoms that may persist for up to two weeks or longer. 14 It is generally recommended that a person stay off work or school until two days after symptoms have cleared. However, because the bacteria may still be present in a person’s stools for several days or weeks after symptoms have disappeared, it is very important to maintain good personal hygiene and wash the hands thoroughly after using the toilet and before touching food. This is especially important for people who work with food, e.g. in restaurants. Regulations differ among countries, but in some cases, a stool test may be required to confirm that the person is no longer infectious. 15
Q: How can I tell if it is bacterial gastroenteritis or viral gastroenteritis?A: In most cases of gastroenteritis, it is not necessary to find out whether the cause of the stomach bug is viral or bacterial, as the treatment is largely the same and is aimed at providing relief from symptoms. However, in some cases, if symptoms are severe or do not clear up, a doctor may recommend tests to identify the cause and prescribe a specific treatment, such as antibiotics. 6 2 16 17
Q: Bacterial gastroenteritis vs. food poisoning – what is the difference?
A: Though definitions may vary, food poisoning is a broad term for illness that arises from contaminated food or drink. Food poisoning can be caused by a variety of bugs, including viruses, bacteria and parasites, as well as toxins. If bacteria are the cause of the condition, the term bacterial gastroenteritis may be used. Sometimes the terms bacterial gastroenteritis and bacterial food poisoning are used interchangeably. Though many cases of bacterial gastroenteritis are caused by contaminated food, this is not true of all of them; in some instances, the bacteria may be transmitted directly from live animals, or from one person to another. 18 19 20
Q: Do I need antibiotics for food poisoning?
A: Food poisoning can be caused by a number of different organisms, including viruses and bacteria. Antibiotics are not effective against viruses, and in most cases of bacterial food poisoning, antibiotics are not needed or recommended. Antibiotics are typically only recommended where symptoms are severe or persistent, or the person has a weakened immune system, or is maybe at risk of developing complications for other reasons. They may also be recommended for some cases of traveler’s diarrhea, as well as C.diff infections. 2 11
Q: Should I be worried about “traveler’s diarrhea”?
A: Traveler’s diarrhea is a name given to episodes of gastroenteritis, most commonly bacterial gastroenteritis, which develop during or shortly after travel abroad. The main symptom is diarrhea, which is typically watery, though nausea, vomiting and abdominal pain may also occur. Most cases of traveler's diarrhea are relatively mild and can be managed without the need for medical advice. Dehydration is the main risk, so it is important to consume plenty of fluids and get sufficient rest. Medical advice should be sought in any of the following situations: 12
- A fever is present
- The person passes bloody stool
- There is difficulty replacing fluids because of frequent bouts of diarrhea or vomiting
- There are signs and symptoms of dehydration
- Symptoms last for more than 2-3 days
- Antibiotics have been prescribed, but symptoms have not improved within three days
- The person is a young child, is elderly or has an underlying medical condition
- The person is pregnant.
Q: Is traveler’s diarrhea contagious?
A: Traveler’s diarrhea is often caused by bacteria and can be spread from person to person where good personal hygiene is not maintained. However, it is usually transmitted through contaminated food or beverages. 21
Q: Can you have bacterial gastroenteritis without diarrhea?
A: Diarrhea or loose bowels is typically, though not always, the main symptom of a bacterial stomach bug. There are many different possible causes of gastroenteritis, including viruses (see viral gastroenteritis), and not every type of stomach flu will result in diarrhea in every person. 22 If you think that you might have a case of gastro, you can try using the Ada app to find out more about your symptoms. Many other health conditions can cause gastrointestinal symptoms that may be mistaken for gastroenteritis.
Q: Can you have bacterial gastroenteritis with diarrhea as the only symptom?
A: Symptoms of bacterial gastroenteritis vary in type and severity, and some people may experience diarrhea without other symptoms, such as abdominal pain or nausea.
Other names for bacterial gastroenteritis
Bacterial gastroenteritis is sometimes also known as:
- Stomach flu
- Stomach bug
- Traveler’s diarrhea, sometimes written as travelers’ diarrhea or travellers’ diarrhea
- Infectious diarrhea
- Montezuma’s revenge (may be considered inappropriate)
- Food poisoning or foodborne illness.