Acute Infectious Diarrhoea Overview

Acute Infectious Diarrhoea

• Acute diarrhoea is defined as an increase in stool frequency or a change in stool consistency lasting less than 14 days.
• Most cases are viral and self-limiting, resolving without specific treatment.
• Clinical clues for differentiating between viral, bacterial, and toxin-mediated diarrhoea are summarised in Table 2.4.
• Viral causes (e.g., rotavirus, norovirus) are often associated with a history of contact with a person with diarrhoea, outbreaks, and prominent upper gastrointestinal symptoms (vomiting, nausea).
• Bacterial causes (e.g., Campylobacter enteritis, Clostridioides difficile) are more likely with fever, tenesmus (straining to defecate), and bloody stool. Travellers with diarrhoea frequently have a bacterial aetiology.
• Toxin-mediated cases (e.g., Staphylococcus aureus, Bacillus cereus) present with a short incubation period (typically several hours), vomiting, nausea, and abdominal pain, with diarrhoea occurring later.
• Immunocompromised individuals are susceptible to a wider range of pathogens (bacteria, viruses, parasites).

Faecal Testing

• Faecal testing is only appropriate if results will aid management.
• It's recommended in patients with bloody stools, moderate to severe disease, prolonged symptoms, and immunocompromised individuals.
• Traditional faecal testing (culture, microscopy, antigen testing) still plays a role but is less sensitive compared to multiplex PCR. The positive results from bacterial cultures can be used for susceptibility testing and epidemiological assessment.
• Multiplex PCR tests are widely available as a culture-independent method. They screen for a broad range of pathogens, provide rapid results, and have improved sensitivity over traditional methods. Although positive results do not always indicate disease, useful information about the causative bacteria, and antimicrobial susceptibility testing is possible.
• Microbiological tests performed on faecal samples vary between laboratories and each uses its own algorithms.

Severity of Acute Infectious Diarrhoea

• Severity relates to the degree of functional incapacity. Mild cases allow for normal activity, moderate cases require adjustments to activities, and severe cases lead to incapacity and may require hospitalisation.
• Specific clinical features suggestive of severity include high fever, tachycardia, leucocytosis, abdominal tenderness, severe abdominal pain, high volume diarrhoea with hypovolaemia, bloody stool, or prolonged symptoms.

Empirical Antibiotic Therapy

• Empirical antibiotics are generally not indicated for community-acquired infectious diarrhoea.
• An exception is for patients with severe disease (see specifics related to severity) or immunocompromised patients.
• Patients with bloody diarrhoea without fever or sepsis, or are immunocompromised are not always given empirical antibiotics.

Specific Infectious Pathogens

• Individual pathogens like Campylobacter, Clostridioides difficile, Enterohaemorrhagic Escherichia coli, Salmonella, Shigella, Vibrio cholerae, Vibrio non-cholera species, Cytomegalovirus, Cryptosporidium, Cyclospora, Cystoisospora (Isospora) belli, Microsporidia are mentioned with diagnostic criteria.

Treatment and Rehydration

• Rehydration is the primary treatment goal. Oral rehydration is generally sufficient unless severe dehydration is present.
• Details of rehydration, probiotics, antiemetics, antidiarrhoeal, and zinc supplementation are found in corresponding guidelines.
• Indications for empirical antibiotic therapy, regimen, and duration vary based on the severity of disease and causative pathogen. Clostridioides difficile has specific treatment protocols.
• Treatment for recurrence may differ in approach.
• Consider faecal microbiota transplantation when indicated in specific patient groups; for example, cases of recurrence, or ongoing refractory disease.

Other Key Information

• Patients with suspected cases of infectious diarrhoea should have faecal specimens analyzed as appropriate.
• There is a risk for antimicrobial resistance in some pathogens, and clinicians should note local resistance levels when choosing treatments in specific pathogens.
• Severity guidelines can aid in determining appropriate interventions.
• Certain situations warrant expert advice (severe disease, immunocompromised patients, or those lacking responses to treatment).