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Diarrhoeal Diseases Caused by Microbes

Essentials

  • In acute diarrhoea, ensuring adequate hydration is essential.
  • Antimicrobial treatment is usually unnecessary.
  • Antimicrobial therapy has not been shown to prevent rare secondary diseases (e.g. reactive arthritis).
  • Treatment depends on the causative organism and the clinical picture.
  • Doctors must report the following dangerous communicable diseases causing diarrhoea: Shigella dysentery, EHEC infection and cholera. The following systemic diseases causing fever belong to the same group: typhoid fever (Salmonella Typhi) and paratyphoid fever (Salmonella Paratyphi A, B or C), which may have diarrhoea as a symptom. National differences may apply. Check local requirements concerning reporting of these diseases.
  • For causes and clinical pictures of food poisoning, see Food poisoning Food Poisoning.
  • See also Acute diarrhoeal disease in a traveller Acute Diarrhoeal Disease in a Traveller and Prolonged abdominal complaints in travellers Prolonged Abdominal Complaints in Travellers.
  • Notice that country-specific variation exists concerning the epidemiology of these pathogens. Find out about local epidemiology.

Diagnosis of diarrhoeal diseases

  • Diagnostics: see Acute diarrhoeal disease in a traveller Acute Diarrhoeal Disease in a Traveller
  • Microbiological examination is usually unnecessary.
  • If antimicrobial treatment is considered, microbiological samples are taken first.
  • Virus tests are usually only performed when investigating epidemics.
  • Tests for faecal parasites should normally only be performed if diarrhoea is prolonged (see Prolonged abdominal complaints in travellers Prolonged Abdominal Complaints in Travellers).

Supportive care of patients with diarrhoea

  • Treatment is based on rest and rehydration.
  • Healthy adults can normally be rehydrated at home. Beverages such as diluted juices, tea, vegetable broth, water, and berry sauces can be recommended. Patients should not drink only sweet soft drinks or too much of them, as these may cause osmotic diarrhoea. Small quantities of food can be eaten. Eating will not worsen the diarrhoea.
  • Dehydration can be prevented and treated with products intended for restoring fluid and salt balance that are available at pharmacies.
  • Loperamide can be used for short-term symptomatic treatment (for 2 days). However, it is not suitable for patients with high fever or bloody diarrhoea, as these may suggest disease caused by invasive bacteria (Salmonella, Shigella) that may even be aggravated by loperamide.
  • Children, the elderly and those with underlying diseases are prone to complications caused by dehydration and must be observed particularly closely. See also the article on Diarrhoea and vomiting in children Diarrhoea and Vomiting in Children.

Indications for hospitalization

  • If there is severe abdominal pain or obvious tenderness on abdominal palpation, the possibility of a surgical condition must be borne in mind.
  • Impaired general condition
  • High fever and/or poor general condition (e.g. Salmonella sepsis)
  • Dehydration that is severe enough to require intravenous fluid administration
  • Carditis, pancreatitis, meningitis, cholecystitis or other severe complication in association with diarrhoea
  • Arthritis with severe symptoms
  • Fever and travelling in a tropical country (malaria must be excluded, and ceftriaxone, which is active against S. Typhi, should be given empirically).
  • Guillain-Barré syndrome (after Campylobacter enteritis)

High-risk occupations and infectious diarrhoea

  • High-risk occupations are ones where an infected employee could cause widespread infection or where people infected are more likely to develop complications.
  • The definition of high-risk occupations, related policies and testing protocols to prevent further infections vary from country to country. Find out about local definitions and requirements.
  • An employee developing gastroenteritis/diarrhoea must stop working on high-risk tasks regardless of the cause of the condition.
  • The employee may return to work after 2 days with no symptoms, unless stool sample has shown Salmonella, EHEC or Shigella. Carriers of these microbes must not continue in their work until samples are clear.
  • In salmonellosis, the collection of follow-up specimens for culture should be started no earlier than one week after the positive faecal culture result was obtained. Samples should be taken once a week until the first negative sample and then every two days. The patient must not return to work until 3 consecutive negative samples have been obtained.

EAEC, EPEC, ETEC

  • EAEC = enteroaggregative E. coli, EPEC = enteropathogenic E. coli, ETEC = enterotoxigenic E. coli
  • These are the most common faecal pathogens in travellers with diarrhoea.
  • These pathogens cannot be found by the standard stool culture.
  • Can be found with nucleic acid detection tests.
  • Sometimes EAEC and EPEC may be found in stools several months after travel without causing symptoms. Hence, detecting them in a patient with long-lasting diarrhoea does not always demonstrate a cause-effect relationship.
  • Treatment: rest and rehydration. Most cases are self-limiting and resolve without antimicrobial treatment.
  • However, if antimicrobial treatment is required, ciprofloxazin (500 mg twice daily for 1-3 days) or azithromycin (500 mg once daily for 3 days) is recommended.
  • Oral cholera vaccine (Dukoral® ) also gives short-term cover against some ETEC strains.

Enterohaemorrhagic Escherichia coli (EHEC) Antibiotic Treatment of E. Coli O157:h7 Infections

  • Produces Shiga toxin, also known as verotoxin (Stx1 or Stx2), causing the symptoms of the disease.
  • In Finland, all strains are referred to as EHEC. In other countries, this abbreviation is used for strains producing the severe form of the disease, while those causing no or mild symptoms are called STEC and VTEC.
  • Spread through food, particularly raw minced meat, unpasteurized milk and unrinsed vegetables; most often derived from cattle faeces
  • The infecting dose is very small and may also be transmitted through contact.
  • Extensive epidemics may occur.
  • May cause bloody diarrhoea without fever (Stx2). However, it may also be found in the faeces of travellers with few or even no symptoms.
  • Bloody diarrhoea may at worst (in less than 10% of cases) lead to severe renal dysfunction (haemolytic-uraemic syndrome, HUS) or thrombotic thrombocytopenic purpura (TTP).
  • Treatment with antimicrobial drugs is not recommended because the breakdown of bacteria will cause sudden extensive release of toxins.
  • If a patient develops bloody diarrhoea, or if EHEC is suspected, a stool sample should be cultured for EHEC and examined for toxins. A preliminary result should be available within one working day after receiving the sample. The cultured strain is tested for toxin (Stx1 and Stx2) by PCR.
  • EHEC may also be identified by nucleic acid detection tests meant to detect faecal pathogens by analysing EHEC and other bacteria that cause diarrhoea (nucleic acid detection combined with culture of positive findings).
  • As EHEC infection is classified as a dangerous communicable disease, the doctor should submit a disease notification to the health authorities.

Enteroinvasive E. coli (EIEC) and Shigella

  • Enteroinvasive E. coli and Shigella have similar virulence plasmids. Both invade the intestinal wall and may cause painful bloody diarrhoea (dysentery).
  • Despite its invasiveness, Shigella hardly ever enters the circulation, which makes bacteraemia extremely rare. There are no long-term carriers.
  • Four species: S. flexneri, S. sonnei (the most common ones), S. dysenteriae and S. boydii
  • Nearly all patients diagnosed with Shigella in Finland were infected abroad.
  • Nucleic acid detection test to detect faecal pathogen covers both EIEC and Shigella, but does not differentiate between them (result EIEC/Shigella). Shigella is confirmed in the laboratory through cultures.
  • Standard stool culture will detect Shigella but not EIEC. Shigella easily dies in a sample and may therefore remain undetected.
  • The infective dose is small and the disease is easily transmitted.
  • The need for antimicrobial therapy is assessed based on the patient's symptoms. An asymptomatic or mild disease is not treated with antimicrobials, unless there are other reasons for such treatment (immunosuppression, particular risk of transmission). Multiple resistance is common. Ciprofloxazin (500 mg twice daily for 3 days) and azithromycin (500 mg once daily for 3 days) are alternatives. Resistance against both of these drugs occurs.
  • It is important that an infected person follows good hand hygiene, especially when using the toilet.
  • There is no vaccine available against Shigella.
  • As Shigella infection is classified as a dangerous communicable disease, the doctor should submit a disease notification.

Salmonella Typhi and Paratyphi

  • Salmonella Typhi causes typhoid and S. Paratyphi paratyphoid fever. These systemic diseases with fever sometimes cause constipation or diarrhoea, usually only at later stages.
  • The symptoms of typhoid and paratyphoid fever are similar: 1-2 weeks after infection, the patient develops a headache, fever, malaise, abdominal pain, nausea and sometimes relative bradycardia (i.e. heart rate below 100 even with a body temperature exceeding 39°C). Fever usually rises slowly, within several days.
  • Diagnosis is based on positive blood culture. The pathogens or their nucleic acids may sometimes be found in faeces as well (nucleic acid detection combined with culture of positive findings).
  • If these diseases are suspected, ceftriaxone is recommended, if microbiologically confirmed, azithromycin or ciprofloxazin should additionally be given Fluoroquinolones for Treating Typhoid and Paratyphoid Fever (Enteric Fever) (based on sensitivity testing; strains acquired from the Indian peninsula are nowadays often resistant to fluoroquinolones). See also national or local guidance.
  • Two types of vaccine are available against typhoid fever, a live vaccine for oral administration (Vivotif® ) that can also give some protection against paratyphoid fever, and an injectable vaccine (Typherix® , Typhim VI® ). In addition to these, a combination vaccine that protects against typhoid fever and hepatitis A is also available (ViATIM® )
  • As typhoid and paratyphoid fever are classified as dangerous communicable diseases, the doctor should submit a disease notification.

Salmonellas causing enteritis

  • There are more than 2 500 serotypes, of which S. Enteritidis and S. Typhimurium are the most common worldwide.
  • In Finland, approximately 2 000 cases are diagnosed annually, with most of the patients infected abroad.
  • The infection is foodborne. A large inoculum is necessary to cause an infection, and the bacteria must therefore be able to multiply in food before being capable of causing an infection.
  • The most common form of disease is enteritis with sudden diarrhoea, abdominal pain and fever.
  • The infection is usually restricted to the intestine but bacteraemia is also possible.
  • Diagnosis is based on stool nucleic acid detection test (nucleic acid detection combined with culture of positive findings).
  • Resistance is common. Antimicrobial therapy is usually not necessary, unless the clinical picture (suspicion of a systemic infection, prolonged disease) or patient-specific special features (significant primary disease, a child patient less than 1 year old or an elderly patient) demands it. Salmonella diarrhoea with moderate or severe symptoms is usually treated with ciprofloxazin (500 mg twice daily for 3 days) or azithromycin (500 mg once daily for 3 days) if the strain is sensitive to the specific drug. When symptoms subside, no follow-up sample is needed unless the person has a high-risk occupation (see above).
  • Treatment of Salmonella carriers: if the carrier state persists for more than a year, eradication therapy should be considered and carried out after consulting a specialist in infectious diseases.
  • Blood culture-positive salmonellosis is treated with an intravenous antimicrobial drug.
  • For Salmonella carriers in high-risk occupations, an epidemiologist or a specialist in infectious diseases responsible for the relevant region should be consulted.

Campylobacter

  • In industrialized countries, Campylobacter infection is one of the most common causes of bacterial diarrhoea.
  • Animals are usually the source of infection, through either insufficiently cooked meat, particularly chicken/broiler, or drinking water contaminated by the bacteria, abroad also through unpasteurized milk.
  • Campylobacter jejuni is the causative organism in 90-95% of cases, C. coli in 10-15%. 70% of patients are infected abroad.
  • Even low doses are infective. The incubation period is 1-7 days.
  • The disease causes an acute diarrhoea, often with severe abdominal pain and fever. The diarrhoea lasts for 3-5 days, and recovery is mostly spontaneous, but the feeling of being unwell may last for significantly longer.
  • Bacteraemia is rare (1%); a specialist in infectious diseases should be consulted in such cases.
  • Diagnosis should be based on nucleic acid detection test (nucleic acid detection combined with culture of positive findings).
  • If the symptoms of gastroenteritis have already been alleviated or they are mild when the aetiology is confirmed, no antimicrobials are needed. However, if the patient's symptoms require treatment with an antimicrobial, the primary choice is a macrolide (e.g. azithromycin 500 mg once daily for 3 days). Fluoroquinolone resistance is common in many countries.

Yersinia

  • Yersinia bacteria live in animals, particularly pigs. Transmission to humans occurs via food contaminated with Yersinia.
  • Human infections are caused by Y. enterocolitica, Y. pseudotuberculosis or Y. pestis.
  • In patients with diarrhoea, the causative agent is usually Y. enterocolitica and sometimes Y. pseudotuberculosis.
  • The historically significant plague or Black Death was caused by Y. pestis. Bubonic plague is the most common form and pneumonic plague the most feared form of the disease.
  • The incubation period of diarrhoea is 4-6 days.
  • Some of the infections cause mild or febrile enteritis, others mesenteric lymphadenitis, which may mimic appendicitis.
  • Yersinia enteritis usually resolves spontaneously. However, reactive arthritis may develop as a post-infection complication particularly in patients who are HLA-B27 positive.
  • Diagnosis is based on nucleic acid detection test (nucleic acid detection combined with culture of positive findings).
  • In severe cases, the first choice treatments are either fluoroquinolones or ceftriaxone.
  • See also article Yersiniosis Yersiniosis.

Vibrio cholerae

  • Rare in the EU/EEA, including as a cause of traveller's diarrhoea.
  • Transmission occurs via water or food.
  • The symptoms are caused by the toxin secreted by the bacteria.
  • The incubation period varies from several hours to several days.
  • Symptoms include an abrupt onset of painless diarrhoea and copious watery stools.
  • The majority of cases are relatively mild and self-limiting. At worst, however, the disease may lead to hypovolaemia, acidosis and shock in a few hours.
  • Cholera is a dangerous communicable disease, and if it is suspected, a microbiology laboratory should be contacted for instructions regarding sample collection.
  • Nucleic acid detection tests to detect faecal pathogens used in some laboratories are able to detect also V. cholerae. A positive test result requires that cholera toxin is determined as an additional investigation, since strains that do not produce toxin do not cause disease.
  • The essential aspect of treatment is replacement of lost fluid and electrolytes. Rehydration is usually provided by giving oral rehydration solutions (ORSReduced Osmolarity Oral Rehydration Solution for Treating Cholera), in severe cases by intravenous fluid therapy.
  • The antimicrobials used are fluoroquinolones and tetracycline.
  • An inactivated oral vaccine (Dukoral® ) is recommended preventively for those travelling to places with a particularly poor level of hygiene (e.g. refugee camps).
  • As Cholera infection is classified as a dangerous communicable disease, the doctor should submit a disease notification.

Clostridioides difficile

  • Antibiotic-associated diarrhoea may be due to Clostridioides difficile.
  • See separate article on Clostridioides difficile associated diarrhoea Clostridioides Difficile Diarrhoea.

Rotavirus

  • In Finland, the epidemic season starts at the beginning of the year and continues until early summer.
  • Clinical disease is common in children aged more than 6 months, rare in adults. Epidemics occur in nursing homes.
  • The incubation period is 2-3 days.
  • Symptoms are watery diarrhoea, fever and vomiting.
  • The disease usually lasts less than 5 days, and the virus then continues to be excreted in faeces for about another week.
  • Many methods are available for the isolation of rotavirus from stool samples.
  • In Finland, children are vaccinated at the ages of 2, 3 and 5 months with an effective vaccine containing live attenuated viruses Vaccines for Preventing Rotavirus Diarrhoea: Vaccines in Use. Since the vaccine has been taken into use, the number of cases of diarrhoea has decreased significantly.

Norovirus

  • Norovirus is a calicivirus. Epidemics occur mostly in late winter.
  • Norovirus is one of the most common causes of diarrhoeal disease in adults.
  • It is often the cause of gastroenteritis in children.
  • The incubation period is 12-36 hours.
  • Symptoms of the disease include often profuse vomiting and simultaneous diarrhoea and low-grade fever.
  • The disease usually continues for no more than 2 days but excretion of the virus in faeces will continue for about a month.
  • Immunity is not long-lasting; the same virus may already cause a new infection after about 6 months.
  • Diagnosis is challenging, gene amplification being the best method and mainly indicated in the investigation of epidemics.
  • No vaccine is available.

Parasites

  • Of protozoa that cause diarrhoea, Dientamoeba fragilis and Giardia intestinalis are common causative agents.
  • In prolonged diarrhoea in travellers, intestinal parasites should be looked for (see Prolonged abdominal complaints in travellers Prolonged Abdominal Complaints in Travellers).
  • The clinical picture may also consist of an acute severe diarrhoeal disease, especially in Cryptosporidium infections. Also in giardiasis and dientamoebiasis the symptoms may start as an acute diarrhoea.
  • Most patients have been infected abroad; Dientamoeba fragilis can be acquired either from home country or abroad alike.
  • For diagnosis, see Prolonged abdominal complaints in travellers Prolonged Abdominal Complaints in Travellers.
  • See also separate articles on giardiasis Giardiasis, amoebiasis Amoebiasis, cryptosporidiosis Cryptosporidiosis and dientamoebiasis Dientamoebiasis in Adults.