138.1 🎓 醫孞生版

138.1.0.1 📌 䞀頁重點

  • 分類:
    • Non-inflammatory (watery): viral (norovirus, rotavirus), ETEC, V. cholerae, Giardia, Cryptosporidium
    • Inflammatory (dysenteric): invasive bacteria — Shigella, Salmonella, Campylobacter, EHEC, EIEC, C. difficile, Entamoeba histolytica
  • Food poisoning preformed toxin (< 6 hr onset, no fever): S. aureus, B. cereus (rice), C. perfringens (meat reheated)
  • 腹瀉 ≥ 14 d → 持續性 / 慢性 — 想 Giardia, Cryptosporidium, post-infectious, IBS-D
  • Antibiotic 颚險 (avoid empirical):
    • EHEC O157:H7: antibiotic ↑ HUS risk (Shiga toxin release)
    • Salmonella non-typhoidal: antibiotic 延長 carriage
  • Cholera, traveller’s, severe Shigella: 絊 antibiotic

138.1.0.2 1⃣ Pathogens — Quick Reference

病原 䟆源 特埵 治療
Norovirus 逐廳、cruise ship, daycare 急速嘔吐 + 腹瀉, 12-48 hr Supportive
Rotavirus 兒童 (vaccination decreased) 兒童 watery Supportive
ETEC Travel (Mexico, India) Travelers diarrhea Azithro / Cipro × single dose
V. cholerae Endemic, contaminated water “Rice water” stool, massive dehydration ORS critical + tetracycline/doxy/azithro
Shigella Person-to-person, day care Dysentery (blood mucus), low inoculum (10 organisms) Azithro or ciprofloxacin
Salmonella non-typhoidal Poultry, eggs, reptiles Diarrhea + fever Avoid antibiotic (prolongs carriage); severe → ciprofloxacin
Salmonella typhi Travel Typhoid: sustained fever, rose spots, GI later Ceftriaxone or azithro (resistance rising)
Campylobacter Poultry undercooked Bloody diarrhea + fever Azithro 500 mg × 3 d (cipro resistance high)
EHEC (O157:H7) Undercooked beef, raw milk Bloody diarrhea, HUS risk NO antibiotic (HUS risk); supportive
C. difficile Healthcare, antibiotic exposure Pseudomembranous colitis Vancomycin PO or Fidaxomicin (Ch 139)
B. cereus Reheated rice (emetic), meat (diarrhea) Emetic 1-6 hr; diarrheic 8-16 hr Supportive
S. aureus Picnic food, mayo Vomiting < 6 hr preformed toxin Supportive
C. perfringens Reheated meat in cafeteria Diarrhea 8-12 hr Supportive
Giardia Travel, mountain stream Foul-smelling, foamy, weight loss Metronidazole or tinidazole or nitazoxanide
Cryptosporidium Pool water, immunocompromised Watery; AIDS chronic Nitazoxanide (rest supportive)
Entamoeba histolytica Travel, MSM Bloody (amoebic dysentery); + liver abscess Metronidazole + paromomycin

138.1.0.3 2⃣ 評䌰 + Workup

138.1.0.3.1 History (key questions)
  • Duration (acute < 14 d vs 慢性)
  • Stool character: watery vs bloody mucus
  • Symptoms: fever (invasive), vomiting (toxin / viral)
  • Exposure: 逐廳, daycare, healthcare, travel, animal, drink water
  • Risk groups: immunocompromised, elderly, pregnant
138.1.0.3.2 Physical
  • Dehydration (skin turgor, mucous, vital signs)
  • Abdominal exam (tenderness, peritonitis)
  • Rectal exam (bloody, perianal disease)
138.1.0.3.3 Workup (selective)
  • Stool culture / PCR multiplex: severe, bloody, fever, immunocompromised, hospitalized, travel
  • C. diff PCR / GDH + toxin if antibiotic exposure
  • Ova & parasites (O&P) if travel, MSM, immunocompromised, persistent
  • Blood culture if febrile, immunocompromised, suspected bacteremia (Salmonella typhi)
  • CT if peritonitis / megacolon
  • Stool WBC / lactoferrin / calprotectin: 區分 inflammatory vs non-inflammatory

138.1.0.4 3⃣ Treatment

138.1.0.4.1 Supportive (cornerstone)
  • Oral rehydration (WHO ORS)
  • IV fluid if severe
  • Antiemetic (ondansetron) if vomiting
  • Loperamide: OK in non-bloody, no fever; AVOID in bloody / suspect C. diff / Shiga toxin
138.1.0.4.2 Empirical Antibiotic (selective)
  • Travelers diarrhea moderate-severe: Azithromycin 1g single dose (preferred over cipro due resistance)
  • Severe bacterial enteritis (high fever, bloody, sepsis): ceftriaxone or cipro
  • Shigella: azithro or cipro
  • Campylobacter: azithro (cipro resistance > 70% in Asia)
  • Salmonella: only if severe / immunocompromised
  • EHEC: DO NOT treat with antibiotic
  • C. diff: vancomycin PO or fidaxomicin (Ch 139)
138.1.0.4.3 When to avoid antibiotic
  • EHEC O157:H7 (HUS risk!)
  • Salmonella non-typhoidal (delays clearance)
  • Viral diarrhea (no benefit)
  • Mild self-limited

138.1.0.5 4⃣ Food Poisoning by Onset

Onset Toxin / Organism Symptoms
1-6 hr S. aureus, B. cereus emetic Vomiting predominant, preformed toxin
8-16 hr C. perfringens, B. cereus diarrheic Diarrhea, in vivo toxin
> 16 hr Salmonella, Campylobacter, EHEC, V. cholerae, Shigella Inflammatory enteric
> 72 hr (slow) Listeria, Cyclospora, Cryptosporidium Subacute