What is Bacterial Gastroenteritis?
“Gastroenteritis” comes from two Greek terms: gastron, which means “stomach,” and enteron, referring to the “small intestine.” Together, they define gastroenteritis as an inflammation of the stomach and small intestine. Medically speaking, gastroenteritis is seen as a disease that causes diarrhea. This can mean more frequent bowel movements, often accompanied by vomiting, fever, and abdominal pain. More frequent bowel movements are classified as three or more watery or loose stools within a day or at least 200 grams of stool in a day. Gastroenteritis can be categorized in different ways, but one common method is by the length of time symptoms last:
* Acute gastroenteritis lasts for 14 days or less.
* Persistent gastroenteritis lasts between 14 and 30 days.
* Chronic gastroenteritis lasts more than 30 days.
Recurrent gastroenteritis refers to diarrhea that comes back after a symptom-free period of 7 days.
What Causes Bacterial Gastroenteritis?
Gastroenteritis, a condition causing diarrhea and vomiting, can be due to bacteria, viruses, fungi, or parasites. This summary will specifically look at bacterial causes. What triggers infectious diarrhea can change based on geography, whether you live in a city or countryside, any other health conditions, and how effective your immune system is.
Contrary to what you may expect, the most common cause of sudden infectious diarrhea is actually viruses (such as norovirus, rotavirus, and adenovirus). This is supported by the fact that only less than 5% of stool tests show bacteria. Other significant causes of watery diarrhea include bacteria like Clostridium perfringens and Escherichia coli (ETEC).
That being said, bacteria tend to cause more severe diarrhea conditions than viruses or other infections. In a study, it was found that in healthy adults who suffered severe diarrhea – defined as at least four wet or loose stools a day for three days or more – bacteria were found in 87% of cases.
Looking specifically at these severe bacterial causes, non-typhoidal Salmonella and Campylobacter spp are the most common in the United States. In 2016, the Centers for Disease Control and Prevention found that for every 100,000 people, there were 15.4 cases of Salmonella, 11.8 cases of Campylobacter, 4.6 cases of Shigella, 2.8 cases of Shiga toxin-producing E.coli, 0.45 cases of Vibrio, 0.42 cases of Yersinia, and 0.26 cases of Listeria.
Risk Factors and Frequency for Bacterial Gastroenteritis
Acute infectious diarrhea is a widespread problem worldwide, even in developed countries such as the United States. It’s one of the main reasons for illness across the globe, causing between 1.5 and 2.5 million deaths every year. This condition is especially harmful to children under 5, being the second leading cause of death from infectious diseases for this age group. There are billions of cases affecting children globally each year.
- In the United States, there are over 350 million instances of acute gastroenteritis, a form of diarrhea, each year.
- Of these, food-borne bacteria cause 48 million cases.
- Diarrhea results in 1.5 million primary care doctor visits each year.
- It leads to around 200,000 children under 5 years old being admitted to the hospital annually.
- Although it isn’t often lethal in the United States, diarrhea still results in about 300 deaths each year.
- Compared to developing countries, developed countries like the United States, the United Kingdom, and Canada have fewer hospital admissions due to diarrhea.
It’s also worth noting that It’s also worth noting that over half of the people traveling from developed to developing countries experience traveler’s diarrhea. In the United States, 9 out of 1000 children under 5 years old are admitted to the hospital due to this condition each year. In the UK and Australia, the rate is slightly higher at about 12 admissions per 1000 annually. Moreover, the prevalence of a specific kind of bacteria, Clostridium difficile, is on the rise in both adults and children.
Signs and Symptoms of Bacterial Gastroenteritis
Gastroenteritis is a condition typically marked by symptoms like nausea, diarrhea (which could be watery or even bloody), vomiting, abdominal pain, and sometimes fever. The fever can indicate that harmful invasive organisms are the cause.
During a physical check-up, the doctor might find the patient’s stomach to be soft, but the patient may react defensively to the touch. This can be due to mild to moderate tenderness in the area. The presence of a fever again suggests harmful organisms could be causing the illness. The crucial thing for doctors to check during this examination is the level of hydration. This can help tell when a patient’s condition is severe enough to call for hospital admission. They would look for things like:
- A dry mouth indicating dry mucus membranes
- Loose skin or decreased skin ‘springiness’
- Changes in mental function
- Rapid heartbeat
- Low blood pressure, particularly when changing position from laying down to standing
- Bloody stools
- A recent spell in hospital or use of antibiotics
- Patient over 65 years old
- Existing conditions like HIV and diabetes
Testing for Bacterial Gastroenteritis
At the start, doctors would perform a thorough review of the patient’s food and medical history, as well as examine the nature of their symptoms, such as how long they’ve been occurring and how often. This way, they can begin to identify the cause of the experienced symptoms.
In many cases of bacterial gastroenteritis, which is a stomach bug, no tests might be needed for diagnosis. However, if the patient is severely dehydrated, a serum electrolyte panel may be ordered to check for any imbalances in the body’s electrolytes, which are minerals required for vital bodily functions.
A complete blood count could be helpful too, although it won’t tell which type of bacteria is causing the illness. Rather, it informs doctors about the severity of the illness or if there are any complications. For instance, a high white blood cell count could point to serious bacterial infection or pseudomembranous colitis, which is inflammation of the colon, while low platelet count might suggest the onset of a condition called hemolytic-uremic syndrome.
If the patient has a high fever or other severe symptoms, the doctor may want to take a blood culture, which is a test that checks for bacteria in the blood.
Stool testing could be required if the illness is severe – with signs such as dehydration or severe abdominal pain – or if they are from a high-risk group – such as being over 70, being pregnant, having a weakened immune system or other underlying health conditions. This test can also be done if the patient has other signs of inflammatory diarrhea, like mucus or blood in the stool or a high-grade fever. The standard stool culture can help identify common culprits like Salmonella, Campylobacter, and Shigella bacteria.
If doctors suspect other bacterial pathogens, they might need to do specific microbiology and culture analysis. Additional tests for Shiga toxin and leukocytes (another kind of white blood cell) in the stool should be ordered in case of bloody diarrhea. Lastly, if the diarrhea continues, doctors should also test stool samples for ova and parasites.
Treatment Options for Bacterial Gastroenteritis
Most cases of noninflammatory diarrhea are usually resolved on their own and don’t require any special medical treatment. However, supportive care is recommended to manage the symptoms. This often includes rehydrating the patient, which can be done by encouraging them to drink fluids. If the patient is unable to rehydrate orally or if oral rehydration isn’t effective, they may need to receive fluids through an IV.
While antibiotics can be used to treat diarrhea, they aren’t always necessary or recommended, even when we know bacteria is causing the illness. For example, patients with certain bacteria like the Shiga toxin-producing E.coli may not be given antibiotics. In some severe cases, like when a patient has over six stools in a day, a fever, or needs to be hospitalized, antibiotics such as azithromycin or fluoroquinolones may be used. Antibiotics may also be given to patients over 70 years old, those with a weakened immune system, those with other health conditions, or if there’s blood or mucus in the stool. It’s important to stop taking these antibiotics if E.coli is found.
There are specific antibiotics that work best for certain bacteria. For example, tetracyclines are most effective against Vibrio, and for pregnant patients with a suspected Listeria infection, ampicillin is the preferred treatment. If a C.difficile infection is causing the diarrhea, the patient should stop taking the antibiotic that caused the infection, and a new antibiotic treatment should be started. As per new guidelines from the Centers for Disease Control and Prevention, oral vancomycin or fidaxomicin is recommended for non-severe C.difficile infections over oral metronidazole for severe ones. A combination of oral vancomycin with IV metronidazole should be used for severe C.difficile infections.
For symptom management, loperamide can be given to patients who don’t have a fever and whose diarrhea isn’t bloody. But this should be done with caution.
What else can Bacterial Gastroenteritis be?
When trying to determine the cause of severe bacterial stomach flu, doctors also consider other potential sources. These may include stomach flus caused by viruses or parasites, and common illnesses brought on by contaminated food.
Additionally, there are several other health conditions which can also lead to symptoms like watery diarrhea. This list includes Crohn’s disease (a type of bowel disorder), pseudomembranous colitis (an inflammation of the colon), microscopic colitis (another inflammation of the colon), acute HIV infection, irritable bowel syndrome, and lactose intolerance.
Bloody diarrhea, however, can be a symptom of conditions other than dysentery, such as ulcerative colitis, which leads to ulcers in the digestive tract. Other conditions like celiac disease, which relates to a reaction to eating gluten, and malabsorption syndromes, conditions where one cannot absorb enough nutrients, also commonly result in diarrhea.
Possible Complications When Diagnosed with Bacterial Gastroenteritis
Dehydration and a reduction of electrolytes in the body are typically the most frequent issues after acute gastroenteritis. Chronic diarrhea can also develop from acute gastroenteritis, which might cause lactose intolerance or an overgrowth of bacteria in the small intestine. There are several other complications that may occur after a bout of diarrhea, including:
- An increase in the symptoms of inflammatory bowel disease
- Sepsis, a life-threatening response to infection
- Enteric fever, a type of bacterial infection
- Guillain-Barre syndrome, which often happens after a Campylobacter infection
- Reactive arthritis, especially following infections like Shigella, Salmonella, Campylobacter, or Yersinia
