Q&A: Treatment of Diarrhoea in an Immunocompetent Patient

Diarrhea is generally defined as the passage of three or more unformed stools per day, often in addition to other enteric symptoms, or the passage of more than 250 g of unformed stool per day. On the basis of its duration, diarrhea can be classified as acute (<14 days), persistent (14 to 29 days), or chronic (≥30 days).

This article is for Medical Students & Professionals

This is a Question & Answer revision article designed for medical students and professionals preparing for the PLAB, MRCP or USMLE examinations. They are based on actual questions from these examinations. You may find the Diarrhoea article more useful, or one of our many articles on Diseases & Conditions, Medical Syndromes, Health & Wellness or Home Remedies.

In this article:
Acute infectious diarrhea in immunocompetent adults
MCQ exams: clinical scenario
MCQ exams: answer
MCQ exams: explanations

Acute infectious diarrhea in immunocompetent adults

Gastroenteritis in adults, often due to viral infection involving the stomach and small intestine, is associated with vomiting and diarrhea. In the Western world, noroviruses are the principal cause of gastroenteritis and responsible for approximately 50% of outbreaks of diarrhea, 26% of cases of diarrhea in emergency departments, and 13% of office visits for diarrhea. Noroviruses are particularly common in closed populations such as cruise ships, nursing homes, dormitories, and hospitals.

Challenge experiments involving volunteers and epidemiologic studies show that infections with shigella, Shiga toxin–producing E. coli, noroviruses, rotaviruses, giardia, and cryptosporidium are easily spread by low inoculums of agents that often cause secondary spread of illness. Shigella and noroviruses, the most communicable pathogens, have a high potential for person-to-person spread, which is related to the low amounts of inoculum required, the environmental stability of the organisms, and the common occurrence in young children who are likely to spread infection.

All licensed laboratories are capable of detecting shigella, salmonella, campylobacter, Shiga toxin–producing E. coli O157:H7 strains, giardia, cryptosporidium, Entamoeba histolytica, and rotavirus. For evaluation of bloody diarrhea, a test for the presence of fecal Shiga toxin should also be performed to identify O157:H7 and non-O157:H7 Shiga toxin–producing E. coli strains. Reverse-transcriptase–polymerase-chain-reaction (PCR) assays for the detection of norovirus are available in local public health laboratories in the case of outbreaks.

MCQ exams: clinical scenario

An immuno-competent patient develops diarrhoea. The stool is stained. The slide image shows acid-fast stain on his stool.

The treatment of choice would be:

a) Antiretroviral therapy
b) Metronidazole
c) Vancomycin
d) Albendazole
e) No antibiotics are necessary

MCQ exams: answer

The correct answer is E.
No antibiotics are required for this.

MCQ exams: explanations

Look at the brush border, there are several small spores.

Once believed not to be a pathogen in humans, these little creatures live in the brush border of the gut and are an important cause of diarrhea worldwide. In people who are immunocompromised, it can be hard to shake off the infection.

The most widely used diagnostic test is the modified acid-fast or Kinyoun stain. It is used to detect Cryptosporidium in stool samples. Several immunofluorescent assays are also available, which test for antibodies to the parasite in the blood. Some pharmaceutical companies have produced rapid-result commercial assays, which are moderately successful (~75% detection rate). Polymerase chain reaction (PCR) techniques might also prove to be effective in diagnosing infection.

Treatment usually is not required for cryptosporidiosis in patients who are immunocompetent, and no clinical trials have convincingly demonstrated the efficacy of antimicrobials.

Reference(s)
1). Herbert L. DuPont: Acute Infectious Diarrhea in Immunocompetent Adults. N Engl J Med 2014;370:1532-40. DOI: 10.1056/NEJMra1301069