Management of Suspected Seafood-Borne Gastroenteritis
Begin immediate oral rehydration with reduced-osmolarity ORS (65–70 mEq/L sodium, 75–90 mmol/L glucose) and avoid empiric antibiotics unless the patient has fever ≥38.5°C with bloody stools, recent international travel with sepsis signs, or is immunocompromised with severe illness. 1, 2
Immediate Rehydration Strategy
Oral rehydration is the cornerstone of therapy and takes absolute priority over any other intervention. 1, 2
For mild-to-moderate dehydration (3–9% fluid deficit): Administer 50–100 mL/kg of reduced-osmolarity ORS over 2–4 hours, then continue ORS to replace ongoing losses until diarrhea and vomiting resolve. 1, 2
For severe dehydration (≥10% deficit), shock, altered mental status, or inability to tolerate oral intake: Switch immediately to isotonic intravenous fluids (lactated Ringer's or normal saline). 1, 2
Continue IV fluids until pulse, perfusion, and mental status normalize, then transition to ORS to complete remaining deficit replacement. 1
Total daily fluid intake should be 2,200–4,000 mL/day in adults, exceeding ongoing losses (urine output + 30–50 mL/hour insensible losses + stool losses). 2, 3
Nasogastric ORS administration is acceptable for moderate dehydration when oral intake is refused but mental status is intact. 1, 2
Assessment of Dehydration Severity
Physical examination is the most reliable method to determine hydration status. 4
Mild (3–5% deficit): Slight thirst, mildly dry mucous membranes. 2
Moderate (6–9% deficit): Loss of skin turgor, skin tenting on pinch, dry mucous membranes. 2
Severe (≥10% deficit): Altered consciousness, prolonged skin tenting (>2 seconds), cool extremities, decreased capillary refill, rapid deep breathing (acidosis). 2
Antiemetic Therapy to Facilitate Oral Rehydration
Ondansetron may be given to children >4 years and adults with vomiting to improve ORS tolerance and reduce need for IV fluids. 1, 2
Antiemetics are adjunctive only—they do not replace fluid therapy. 1
Nutritional Management
Resume a normal, age-appropriate diet immediately during or after rehydration; do not withhold food. 1, 2
Continue breastfeeding throughout the illness in infants. 1, 2
Initially favor small, light meals and avoid fatty, heavy, spicy foods, caffeine, and lactose-containing products during the acute phase. 2, 3
Indications for Antibiotic Therapy
Empiric antibiotics are NOT indicated for most cases of seafood-borne gastroenteritis. 1, 2 The vast majority of seafood-related gastroenteritis is viral (norovirus) or caused by self-limited bacterial pathogens that do not benefit from antibiotics. 5
DO NOT use antibiotics if:
Watery diarrhea without fever or blood in an immunocompetent patient. 1, 2
Suspected or confirmed Shiga-toxin-producing E. coli (STEC O157 or other toxin-2 producers)—antibiotics markedly increase the risk of hemolytic-uremic syndrome. 1, 6
DO use empiric antibiotics if:
Fever ≥38.5°C with bloody or mucoid stools (suggests invasive pathogens such as Shigella, Campylobacter, or invasive E. coli). 1, 2
Recent international travel with fever ≥38.5°C or signs of sepsis. 1, 2
Immunocompromised patient with severe illness and bloody diarrhea. 1, 6
Infants <3 months with suspected bacterial etiology or toxic appearance. 1, 2
Clinical features of sepsis with suspected enteric fever (obtain blood, stool, and urine cultures first). 1
Recommended antibiotic regimens (when indicated):
Azithromycin is the preferred first-line agent: 500 mg single dose for watery diarrhea; 1,000 mg single dose for febrile dysentery. 2, 3
Fluoroquinolones (ciprofloxacin 750 mg single dose or 500 mg BID × 3 days; levofloxacin 500 mg single dose or daily × 3 days) are second-line if azithromycin is unavailable or local susceptibility favors their use. 1
Modify or discontinue antibiotics once a specific pathogen is identified. 1, 6
Symptomatic Antimotility Therapy
Loperamide may be used in immunocompetent adults with watery diarrhea ONLY after adequate rehydration: 4 mg initially, then 2 mg after each loose stool, maximum 16 mg/24 hours. 1, 2, 3
Loperamide is absolutely contraindicated in:
Diagnostic Testing (Selective)
Stool microbiological testing is not routinely needed when viral gastroenteritis is the likely diagnosis in mild illness. 4
Obtain stool studies when:
Severe dehydration or illness requiring hospitalization. 2
Immunosuppression. 2
Suspected outbreak or recent hospitalization/antibiotic exposure (to evaluate for C. difficile). 2, 3
Symptoms persist >3 days with fever or severe abdominal pain. 2
Stool panel should include:
Bacterial culture for Salmonella, Shigella, Campylobacter, Yersinia. 2, 3
Shiga-toxin testing (or gene detection) to identify STEC—critical before starting antibiotics if bloody diarrhea is present. 1, 2, 3
C. difficile toxin assay if recent healthcare exposure or antibiotics. 2, 3
Blood cultures if signs of septicemia, suspected enteric fever, or immunocompromised with systemic manifestations. 2, 3
Adjunctive Therapies
Probiotics may be offered to reduce symptom severity and duration in immunocompetent patients. 1, 2, 6
Oral zinc supplementation (10–20 mg daily for 10–14 days) is recommended for children 6 months to 5 years in settings with high zinc-deficiency prevalence or malnutrition. 1, 2
Critical Pitfalls to Avoid
Never prioritize antimotility agents or antibiotics over rehydration—dehydration, not diarrhea, drives morbidity and mortality. 2, 3
Never start antibiotics for bloody diarrhea before ruling out STEC with Shiga-toxin testing. 1, 2, 3
Never use loperamide when fever or bloody stools are present. 1, 2, 3
Never prescribe empiric antibiotics for uncomplicated watery diarrhea—this promotes antimicrobial resistance without clinical benefit. 1, 2
Never delay intravenous rehydration in severe dehydration while attempting oral rehydration. 1, 2
Hospitalization Criteria
Severe dehydration (≥10% deficit) with altered mental status. 1, 2
Failure of oral rehydration therapy plus antiemetic. 4
Inability to tolerate oral intake despite ondansetron. 4