Bacterial diarrhea: the only case where antibiotics can be used
Infectious diarrhea can be caused by bacteria (bacterial diarrhea), parasites (parasitic diarrhea) or viruses (viral diarrhea). In bacterial diarrhea, the bacteria involved are Shigella, responsible for an illness called shigellosis; Vibrio cholerae, responsible for dreaded cholera epidemics; and also Salmonella or Escherichia coli, which sometimes make the headlines in Western countries. This type of diarrhea usually clears up on its own. It is important to stay hydrated and to allow restoration of the gut microbiota's equilibrium over the course of a few weeks. However, in some at-risk populations or when the infection spreads, antibiotics may be necessary, sometimes accompanied by probiotics to restore the gut microbiota.
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About this article
What is bacterial diarrhea?
Diarrhea is defined as the passage of at least three loose or liquid stools per day, and infectious diarrhea is diarrhea caused by infection by a pathogen (virus, bacteria, or parasite) 1-3. If the pathogen is a bacterium, the diarrhea is said to be “bacterial”.
Viral diarrhea, bacterial diarrhea, parasitic diarrhea, they are not the same thing
Under the broad umbrella of diarrhea, while there are some kinds that are non-infectious (e.g. in the case of a digestive disease such as Crohn’s disease), the great majority are caused by a pathogenic infection. Depending on the pathogen involved, we talk about:
- Viral diarrhea if the culprit is a virus (e.g. rotavirus, which affects many infants);
- Bacterial diarrhea if a bacterium is responsible (e.g. Vibrio cholerae, which is responsible for cholera epidemics);
- Parasitic diarrhea if a parasite is the root cause (e.g. the mini-parasite composed of a single cell of Giardia intestinalis, which is responsible for the disease called giardiasis, dreaded by tourists, or the worm known as roundworm, dreaded by parents of young children).
Lastly, diarrhea can also be a common side effect (in up to 35% of patients 4,5) of antibiotic treatment. This is known as antibiotic-associated diarrhea.
Which bacteria are responsible?
The bacteria involved are often6:
- Shigella, responsible for an illness called shigellosis and for 212,438 deaths worldwide in 2016,
- and Vibrio cholerae, responsible for dreaded cholera epidemics and for 107,290 recorded deaths in 2016, generally in poor populations without access to clean drinking water.
However, these are not the only ones. The bacteria Salmonella or Escherichia coli sometimes make the headlines in Western countries when they contaminate foodstuffs (raw ground meat, cheese, etc.) and necessitate much-publicized product recalls from supermarkets.
How do bacteria cause acute diarrhea?
In bacterial diarrhea, as in infectious diarrhea in general, it all begins with a confrontation between a pathogen (in this case a bacterium), transmitted by contaminated food, polluted water or contact with a sick person, and the host (our body). However, the dangerous nature of bacteria varies from one bacterium to another, and behind one name, there are actually many types of bacteria. For example, there are over 2,500 different salmonella strains of varying degrees of aggressiveness7. The same applies to Escherichia coli: not all E. coli are pathogenic, and among those that are pathogenic, there are many different strains2,8.>
The outcome of the confrontation between the bacterium and the body depends on complex equilibriums, which largely involve the gut microbiota. Thus, animals lacking in intestinal flora are very susceptible to bacteria responsible for diarrhea: a micro-dose of certain strains of salmonella is enough to cause a fatal infection, while a dose 100 to 100 million times stronger is necessary to kill mice with intact gut microbiota9. The science behind this difference Without microbiota, the immune system is immature and thus unarmed against an invasion of pathogens, which are also able to freely settle in with no other bacteria occupying the territory9.
When the bacteria get the upper hand, they secrete specific toxins, which explains why each bacterial diarrhea is different2,10:
- the toxin from Shigella destroys the cells of the digestive tract lining and thus causes severe diarrhea containing blood and mucus; <
- the toxin from Vibrio cholerae disrupts the absorption and secretion of ions and water in the digestive tract, causing a very liquid diarrhea rich in ions;
- the different types of E. coli produce different toxins: Enteropathogenic E. coli causes persistent liquid diarrhea (usually among infants), while Enteroinvasive E. coli causes diarrhea containing bile and mucus, etc.
Acute bacterial diarrhea caused by an infectious agent creates a major intestinal dysbiosis2. It will take the microbiota several weeks to recover its equilibrium, which, in some cases, never returns to its initial state2,11.
How to prevent bacterial diarrhea?
Due to the dangerous nature of Shigella, there is hope of a vaccine which could eventually not only prevent the 200,000 or so deaths caused annually by this bacteria, but could also reduce the need for antibiotics and the emergence of resistance that makes treatment ineffective. Several vaccines against Shigella are currently undergoing development, but none are yet officially approved12.
Another research avenue: the gut microbiota. In humans, a “healthy” gut microbiota is considered a means of preventing cholera13<. In addition, probiotics are seen as a means of limiting the severity of some bacterial infections2: the probiotic yeast Saccharomyces boulardii could facilitate the restoration of gut microbiota in children suffering from acute diarrhea14; the probiotic E. coli (non-pathogenic) inhibits the formation of biofilms by pathogenic bacteria, including pathogenic E. coli2; a trio of specific strains of Lactobacillus, Bifidobacterium and Streptococcus reduces the duration of bloody diarrhea (dysentery) and hospitalization2.
To these preventive measures, of course, are added the advice of hygiene and social distancing, which apply to all types of infectious diarrhea (see boxed text). In the specific case of food-borne infections (salmonella, E. Coli), care should be taken to cook food properly (E. coli is killed by heat, which explains why contaminated foods are often raw or undercooked meats).
How to treat bacterial diarrhea?
Quite common and usually not serious, bacterial diarrhea often clears up on its own. Attention should be paid, however, to the risk of dehydration among the very young, the elderly and immunocompromised patients. Loss of water and electrolytes (sodium, potassium and chloride ions) should be compensated for:
- orally (with oral rehydration solutions, or ORS);
- or intravenously in the most serious cases.
Health professionals may also recommend certain probiotic strains to treat acute infectious diarrhea in children. These good bacteria reduce the duration of diarrhea, and/or the duration of hospitalization, and/or the quantity of stools (ESPGHAN 2023).
The specific case of diarrhea caused by C. difficile
The figures are quite staggering: out of 100 patients admitted to hospital, 7 in high-income countries and 15 in low- or moderate-income countries will contract at least one infection during their time in hospital. What's more, on average 1 in 10 affected patients will succumb to an infection, which is said to be nosocomial15.
Of the pathogens involved, the bacterium Clostridioides difficile (also called Clostridium difficile) is the main bacterium responsible for nosocomial infectious diarrhea in adults. Europe records around 120,000 cases per year; the United States about 450,00016.
What is worrying is that over time, increasingly virulent strains of C. difficile, now more resistant to antibiotics, have emerged and the recovery rate has plummeted. Hence the research into alternative treatment methods. According to the 2023 recommendations of the World Gastroenterology Organisation, “probiotics are effective for preventing C. difficile–associated diarrhea in patients receiving antibiotics. ” For recurrent cases of C. difficile in adults and children, fecal microbiota transplantation (FMT) has proved effective17, preventing recurrence in 90% of cases.
Key points to remember about bacterial infectious diarrhea
- Diarrhea is defined as the passage of at least three loose or liquid stools per day, and infectious diarrhea is diarrhea caused by infection by a pathogen (virus, bacteria, or parasite). Due to the resulting dehydration, diarrhea was responsible for 1.6 million deaths in 2016, mainly among malnourished or immunocompromised children or people living with HIV1-3.
- In cases of infection by a bacterium, diarrhea is said to be “bacterial”. The bacteria Shigella (shigellosis) and Vibrio cholerae (cholera) are the deadliest in poor countries without access to clean drinking water. In Western countries, Salmonella and Escherichia coli are associated with food contamination, while C. difficile is the main bacterium responsible for nosocomial infectious diarrhea in adults6.
- Sometimes, the gut microbiota manage to counter the infection; at other times, the bacteria kills the gut microbiota and causes diarrhea of which the characteristics (presence of blood, presence of mucus, passing of a large amount of liquid, etc.) depend on the type of bacteria involved 2,1.
- Prevention of viral diarrhea rests above all on good hygiene practices (washing and cooking of food, hand-washing, social distancing, etc.). Probiotics could have a place in the prevention of certain bacterial infections 2. Lastly, researchers are working on the development of vaccines against Shigella 12.
- treatment of bacterial diarrhea focuses on fighting dehydration.Antibiotics can be prescribed by health care professionals for people at risk (infants, the elderly, immunocompromised patients) or when the infection spreads from the intestines to other parts of the body 7. Probiotics can also be prescribed to reduce diarrhea and hospitalization time(ESPGHAN 2023).
