Gastrointestinal Infections

Gastrointestinal Infections - Bug Parade & Gut Attack

Transmission: Primarily fecal-oral.

Viral Agents:

• Rotavirus: Villous destruction (malabsorptive diarrhea).

  ⭐ Rotavirus is the leading cause of severe dehydrating diarrhea in infants and young children globally.

• Norovirus: Villi blunting (vomiting prominent, outbreaks).

Bacterial Agents: (📌 "Eat Some Campy Vibrio Shigella" - for E.coli, Salmonella, Campylobacter, Vibrio, Shigella)

• E. coli:
  • ETEC: Toxins (Traveler's diarrhea - watery).
  • EPEC: Adherence, effacement (Pediatric diarrhea - watery).
  • EIEC: Invasive (Inflammatory diarrhea - dysentery).
  • EHEC (O157:H7): Shiga-like toxin (Hemorrhagic colitis, HUS).
• Salmonella (non-typhoidal): Invasion, inflammation (poultry, eggs).
• Shigella: Invasion, Shiga toxin (dysentery, low inoculum).
• Campylobacter jejuni: Invasion, cytotoxin (poultry, Guillain-Barré link).
• Vibrio cholerae: Cholera toxin (profuse "rice-water" stools).

Parasitic Agents:

• Giardia lamblia: Villous atrophy, malabsorption (foul fatty stools, contaminated water).
• Entamoeba histolytica: Invasion, flask-shaped ulcers (dysentery, liver abscess).

Gastrointestinal Infections - Symptom Spotlight & Fluid Rescue

• Diarrhea Types:

  • Secretory: Watery, large volume (Cholera, ETEC). Persists with fasting.
  • Osmotic: Stops with fasting, ↑ osmotic gap (Lactose intolerance).
  • Inflammatory: Blood/mucus, fever, pain (Shigella, Salmonella, EHEC).

• Key Symptoms & Red Flags:

  • Symptoms: Diarrhea, vomiting, fever, abdominal pain.
  • Red Flags: Severe dehydration signs, persistent vomiting, bloody/mucoid stools, high fever (>39°C), altered sensorium, abdominal distension, failure of ORT.

• 📌 Mnemonic (Dehydration Assessment): 'ABCD' (Appearance, Breathing, Circulation, Dehydration status/Skin turgor).

• Oral Rehydration Therapy (ORT):

  • Low-osmolarity WHO ORS: Osmolarity 245 mOsm/L.
  • Composition (mmol/L): $Na^+$ 75, $K^+$ 20, $Cl^-$ 65, Glucose 75 (anhydrous, 13.5g/L), Citrate 10.

  ⭐ Low osmolarity ORS reduces stool volume by ~25% and vomiting by ~30% compared to standard ORS.

• IV Fluid Therapy:

  • Indications: Severe dehydration, shock, persistent vomiting despite ORT, inability to take ORT, high stool output (>10 ml/kg/hr).
  • Fluids: Ringer's Lactate (RL) or Normal Saline (NS 0.9%).
  • Bolus: 10-20 ml/kg rapidly; repeat if needed. Severe Malnutrition: 10-15 ml/kg slowly, with caution.

Gastrointestinal Infections - Pathogen Profiles & Bug Busters

• Rotavirus: #1 severe dehydrating diarrhea (infants). Dx: Stool Ag. Rx: ORS. Vaccine.

• Cholera: "Rice-water" stool, severe dehydration. Dx: Culture. Rx: Rehydrate; Doxy (300mg SD) / Azithro (1g SD).

• Shigella: Dysentery, fever. Dx: Culture. Rx: Cipro/Azithro. No anti-motility.

• Salmonella (NT): Watery/bloody diarrhea. Dx: Culture. Rx: Supportive; Cipro if severe/high-risk (<3mo).

• ETEC: Traveler's diarrhea (watery). Dx: Clin/PCR. Rx: Supportive; Rifaximin/Cipro if severe.

• Giardia: Steatorrhea, foul, chronic. Dx: Stool micro/Ag. Rx: Metronidazole (5mg/kg/dose TID).

• E. histolytica: Amebic dysentery, liver abscess. Dx: Stool micro/Ag. Rx: Metronidazole (35-50mg/kg/day) + luminal.

• Stool Tests: Dysentery, severe/persistent (>7d), immunocompromised, outbreak. (Micro, culture, Ag).

• Antimicrobials: Pathogen/severity guided. Empiric if severe. Avoid overuse (↑resistance).

• Adjuncts: Zinc (10mg <6mo/20mg >6mo, 10-14d); Probiotics (LGG, S.boulardii) may ↓ duration.

⭐ Zinc supplementation reduces duration and severity of diarrhea.

High‑Yield Points - ⚡ Biggest Takeaways

• Rotavirus: Most common cause of severe dehydrating diarrhea in young children; vaccine-preventable.
• Cholera: Profuse "rice-water" stools; Oral Rehydration Therapy (ORT) is life-saving.
• Shigellosis: Bloody dysentery, high fever; risk of febrile seizures.
• Typhoid fever: Step-ladder fever, rose spots, relative bradycardia; Salmonella Typhi.
• Amoebiasis: Flask-shaped ulcers, potential for liver abscess; E. histolytica.
• Giardiasis: Foul, fatty stools (steatorrhea), malabsorption.
• EHEC (O157:H7): Causes hemorrhagic colitis and Hemolytic Uremic Syndrome (HUS).