Gastrointestinal · Infectious gastroenterology module; clinical reasoning by organism identification from clinical pattern
By completing this question set, you will be able to classify infectious diarrhea by mechanism (secretory, inflammatory, osmotic) and use that classification to narrow the differential before applying epidemiologic clues. You will use timing of symptom onset after exposure, food source, travel history, antibiotic use, immune status, and animal contact to identify the causative organism from clinical context. You will distinguish toxin-mediated bacterial causes (Staph aureus, B. cereus, C. perfringens, ETEC, Vibrio cholerae) by onset timing, stool character, and food vehicle, and recognize why preformed toxin syndromes are the fastest in onset. You will identify the five invasive bacterial pathogens (Shigella, Salmonella, EHEC O157:H7, Campylobacter, Yersinia) and correctly apply the antibiotic-versus-no-antibiotic decision for each — including the critical EHEC principle of withholding antibiotics entirely. You will recognize Salmonella typhi from its unique clinical features (rose spots, relative bradycardia, constipation before diarrhea, intestinal perforation at Peyer's patches) and identify the correct diagnostic test at each stage of illness. You will diagnose C. difficile infection from its clinical context, stage its severity correctly, apply the treatment algorithm including the fulminant protocol, and select fecal microbiota transplantation (FMT) for recurrent disease — explaining why alcohol-based hand sanitizer fails to prevent transmission. You will distinguish Giardia from Entamoeba histolytica by invasion pattern, stool characteristics, and immune-host vulnerability; identify the additional luminal amebicide step required after metronidazole for E. histolytica; and recognize amoebic liver abscess presenting without diarrhea. You will apply the host immune status framework to identify Cryptosporidium as the most dangerous protozoal diarrhea in HIV patients and explain why restoring immune function (ART) is more important than antiprotozoal therapy. You will identify Cyclospora by its relapsing course and imported produce exposure and select TMP-SMX as the treatment distinguishing it from Cryptosporidium.