What is the best management approach for a patient with persistent symptoms of infectious colitis, including fever, abdominal cramping, and profuse watery diarrhea, despite initial supportive care?

Management of Persistent Infectious Colitis with Fever and Profuse Watery Diarrhea

For this 40-year-old male with persistent symptoms of infectious colitis including high fever (103°F), severe abdominal cramping, and profuse watery diarrhea despite initial supportive care, empiric antibiotic therapy should be initiated immediately while awaiting stool culture results, using either azithromycin 1000 mg as a single dose or a fluoroquinolone (ciprofloxacin 500 mg twice daily for 5-7 days) to cover invasive bacterial pathogens. 1, 2

Clinical Assessment and Diagnostic Approach

The presence of high fever (103°F), severe abdominal pain, and CT-confirmed colitis indicates inflammatory infectious colitis requiring immediate evaluation beyond supportive care alone. 1

Key diagnostic steps to perform now:

• Send stool for multiplex PCR testing (preferred over standard culture) to identify bacterial pathogens including Campylobacter, Salmonella, Shigella, and Shiga toxin-producing E. coli (STEC), as well as Clostridioides difficile toxin assay. 1, 3

• Check for inflammatory markers in stool: fecal leukocytes, lactoferrin, or calprotectin to confirm inflammatory colitis. 1, 2

• Obtain blood cultures if the patient appears systemically ill with persistent high fever, as bacteremia can complicate invasive bacterial enterocolitis. 1

• Test specifically for C. difficile given the severity and persistence of symptoms, even without recent antibiotic exposure, as this can present with severe colitis. 1

Empiric Antibiotic Therapy

Do not wait for culture results before starting antibiotics in this patient with severe, persistent symptoms. The presence of fever >103°F, severe abdominal pain, and CT-confirmed colitis for multiple days warrants immediate empiric treatment. 1, 2

First-line empiric options:

• Azithromycin 1000 mg as a single oral dose is the preferred empiric treatment for febrile dysenteric diarrhea covering Shigella, Salmonella, and Campylobacter. 2

• Alternative: Ciprofloxacin 500 mg orally twice daily for 5-7 days if fluoroquinolone resistance is unlikely (patient has no recent international travel and local resistance rates <10%). 1, 4

Important caveats:

• If Shiga toxin-producing E. coli (STEC/E. coli O157:H7) is suspected (bloody diarrhea with minimal or no fever), do NOT give antibiotics as they may increase risk of hemolytic uremic syndrome by inducing Shiga toxin release. 1

• If C. difficile is confirmed, switch to oral vancomycin 125 mg four times daily for 10 days or fidaxomicin 200 mg twice daily for 10 days. 1

Supportive Care Optimization

Aggressive oral rehydration therapy (ORT) remains the cornerstone even when antibiotics are added. 1

• Administer 2-4 liters of reduced-osmolarity oral rehydration solution (ORS) over 3-4 hours for moderate dehydration in adults. 1

• Consider nasogastric ORS administration if the patient cannot tolerate adequate oral intake but is not severely dehydrated. 1

• Escalate to intravenous hydration if signs of severe dehydration develop (altered mental status, severe orthostatic hypotension, inability to maintain oral intake). 1

• Antiemetic therapy (ondansetron) can be used if nausea/vomiting limits oral intake. 1

• Avoid antimotility agents (loperamide) in patients with high fever and inflammatory colitis, as they may worsen outcomes and increase risk of toxic megacolon. 1

Monitoring and Follow-Up

Clinical improvement should occur within 3-5 days of appropriate antibiotic therapy. 1, 5

Red flags requiring urgent reassessment:

• Persistent fever beyond 72 hours on appropriate antibiotics suggests either resistant organism, inadequate source control, or complications (abscess, toxic megacolon). 5, 3

• Worsening abdominal pain or distension may indicate toxic megacolon or perforation requiring surgical consultation. 1, 3

• Development of bloody diarrhea if not initially present, or increasing blood in stool. 1

Antibiotic adjustment based on culture results:

• De-escalate to narrow-spectrum therapy once specific pathogen and sensitivities are identified (typically within 24-48 hours with multiplex PCR). 1, 5

• For confirmed Campylobacter: azithromycin 500 mg daily for 3 days or ciprofloxacin 500 mg twice daily for 5-7 days (if susceptible). 1

• For confirmed Salmonella or Shigella: ciprofloxacin 500 mg twice daily for 5-7 days or azithromycin 500 mg daily for 3 days. 1, 2

• For confirmed C. difficile: oral vancomycin 125 mg four times daily for 10 days (first-line) or fidaxomicin 200 mg twice daily for 10 days. 1

Common Pitfalls to Avoid

• Do not withhold antibiotics in patients with severe inflammatory colitis (high fever, severe pain, CT-confirmed colitis) while waiting for culture results, as this delays appropriate therapy and worsens outcomes. 1, 2

• Do not give antibiotics empirically for mild watery diarrhea without fever or inflammatory features, as most cases are viral and antibiotics provide no benefit while increasing resistance and C. difficile risk. 1

• Do not use fluoroquinolones if STEC is suspected (bloody diarrhea with minimal fever), as antibiotics may precipitate hemolytic uremic syndrome. 1

• Do not continue antibiotics beyond 5-7 days for most bacterial colitis once clinical improvement occurs, as longer courses do not improve outcomes and increase adverse effects. 1, 5

• Do not assume treatment failure if diarrhea persists for several days after starting antibiotics, as complete resolution typically takes 5-7 days even with appropriate therapy. 1, 3