A patient with HIV has diarrhoea with AF +ve organism in stool. The most likely organism is
**Core Concept**
The patient's symptoms of diarrhoea, along with the presence of an acid-fast positive (AF +ve) organism in the stool, suggest an opportunistic infection in an immunocompromised individual, specifically someone with HIV. This points towards a gastrointestinal infection caused by a Mycobacterium species.
**Why the Correct Answer is Right**
The most likely organism in this scenario is Mycobacterium avium complex (MAC). MAC is a common cause of diarrhoea in HIV-infected individuals, particularly those with advanced immunosuppression. MAC is an acid-fast bacillus that infects the gastrointestinal tract, leading to symptoms such as chronic diarrhoea, weight loss, and abdominal pain. The pathogenesis of MAC involves the invasion of intestinal epithelial cells, leading to an inflammatory response and disruption of the gut barrier.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not match the clinical presentation described. While Cryptosporidium is a cause of diarrhoea in immunocompromised individuals, it is not acid-fast positive.
**Option B:** This option is incorrect because it is not a common cause of diarrhoea in HIV-infected individuals. While Giardia is a cause of gastrointestinal infection, it does not match the acid-fast positive organism described in the question.
**Option C:** This option is incorrect because it is not a common cause of diarrhoea in HIV-infected individuals. While Campylobacter is a cause of diarrhoea, it is not acid-fast positive.
**Clinical Pearl / High-Yield Fact**
MAC infection is often associated with advanced immunosuppression, typically CD4 counts < 50 cells/μL. Early diagnosis and treatment are crucial to prevent morbidity and mortality in these patients.
**Correct Answer:** C. Mycobacterium avium complex (MAC)