What stool studies should be ordered for a patient presenting with diarrhea in Florida?

Stool Studies for Diarrhea in Florida

For patients with diarrhea in Florida, stool testing should be performed for Salmonella, Shigella, Campylobacter, Yersinia, C. difficile, and STEC in symptomatic hosts, with additional testing for Vibrio species in patients with exposure to brackish waters or consumption of raw/undercooked shellfish. 1

Patient-Specific Testing Recommendations

General Approach

• The optimal specimen for laboratory diagnosis is a diarrheal stool sample that takes the shape of the container 1
• A single diarrheal stool specimen is sufficient for most testing; multiple specimens do not increase yield 1
• For bacterial infections, if a timely diarrheal stool sample cannot be collected, a rectal swab may be used 1

Testing Based on Clinical Presentation

Fever, Bloody or Mucoid Stools

• Test for:
  • Salmonella
  • Shigella
  • Campylobacter
  • Yersinia
  • C. difficile
  • STEC (Shiga toxin-producing E. coli) 1

Florida-Specific Considerations

• Test for Vibrio species in patients with:
  • Large volume rice water stools
  • Exposure to salty or brackish waters (common in Florida's coastal areas)
  • Consumption of raw or undercooked shellfish
  • Travel to cholera-endemic regions within 3 days prior to onset of diarrhea 1

Persistent Abdominal Pain

• Test for Yersinia enterocolitica, especially in:
  • School-aged children with right lower quadrant pain mimicking appendicitis
  • Patients with fever at epidemiologic risk for yersiniosis
  • Infants with direct or indirect exposures to raw or undercooked pork products 1

Special Populations

Immunocompromised Patients

• Broader testing is recommended including:
  • Bacterial culture
  • Viral studies
  • Examination for parasites 1
• For AIDS patients with persistent diarrhea, add testing for:
  • Cryptosporidium
  • Cyclospora
  • Cystoisospora
  • Microsporidia
  • Mycobacterium avium complex
  • Cytomegalovirus 1

Travelers

• Diagnostic testing not recommended for uncomplicated traveler's diarrhea
• For diarrhea lasting ≥14 days, evaluate for intestinal parasitic infections
• Test for C. difficile if antimicrobials were taken in preceding 8-12 weeks 1

Hospitalized Patients

• For nosocomial diarrhea (onset after >72 hours of hospitalization):
  • Routine stool cultures and ova/parasite testing are NOT recommended as they have extremely low yield 2, 3
  • Focus on C. difficile testing, especially if antibiotics or chemotherapy were given in recent weeks 1, 3

Outbreak Situations

• Consider a broader set of bacterial, viral, and parasitic agents
• Coordinate testing with public health authorities
• Save culture plates and isolates; freeze whole stools or swabs at -70°C 1

Laboratory Diagnostic Methods

• For bacterial pathogens: Routine stool culture or nucleic acid amplification test (NAAT)
• For STEC: Culture for E. coli O157:H7 and Shiga toxin immunoassay or NAAT
• For C. difficile: NAAT, GDH antigen with/without toxin detection
• For parasites: Ova and parasite examination or specific immunoassays/NAAT
• For viruses: NAAT or EIA depending on the virus 1

Common Pitfalls to Avoid

• Ordering multiple specimens from the same patient rarely provides additional information 4
• Performing stool cultures on patients with nosocomial diarrhea (>72 hours after admission) has extremely low yield and wastes resources 2, 3
• Interpreting results of molecular panels requires clinical consideration as these assays detect DNA and not necessarily viable organisms 1
• Failing to test for Vibrio species in patients with Florida-specific risk factors (coastal water exposure, shellfish consumption) 1