Post-Travel Diarrhea with Negative C. difficile Testing
Given the negative C. difficile test and recurrence of diarrhea after azithromycin, you should obtain stool cultures for bacterial enteropathogens (Campylobacter, Salmonella, Shigella, E. coli O157:H7) and examine stool for parasites (particularly Giardia, Cryptosporidium, Cyclospora, and Entamoeba histolytica). 1
Rationale for This Approach
The clinical scenario suggests traveler's diarrhea that either was not adequately treated or represents a parasitic infection that azithromycin would not cover. The negative C. difficile test is reliable and should not be repeated within 7 days, as the diagnostic yield is only approximately 2% and repeat testing risks false-positive results. 2, 3
Specific Diagnostic Testing
Bacterial Pathogens
- Submit stool culture specifically for Campylobacter jejuni, Salmonella species, Shigella species, and E. coli O157:H7 2, 1
- These are the most frequent invasive enteropathogens causing colitis symptoms in travelers 2
Parasitic Evaluation
- Examine stool for ova and parasites, with specific attention to Giardia, Cryptosporidium, Cyclospora, and Entamoeba histolytica 1
- For travelers with diarrhea lasting 14 days or longer, parasitic testing is specifically recommended 1
- Giardia is particularly important to evaluate when symptoms persist beyond 7 days 2
Important Clinical Considerations
Do NOT Repeat C. difficile Testing
- The IDSA/SHEA guidelines strongly recommend against repeat testing within 7 days during the same diarrheal episode 2, 3
- The proportion of patients transitioning from negative to positive C. difficile within a 7-day window is only 3% 3
- More than 60% of patients remain C. difficile positive even after successful treatment, making "test of cure" meaningless 2, 3
Post-Infectious Considerations
- Post-infectious irritable bowel syndrome can occur following gastrointestinal infections and may explain persistent symptoms even with negative testing 3
- Consider this diagnosis if all infectious workup remains negative but symptoms persist 3
Timing of Evaluation
- Since the patient has already completed azithromycin and symptoms have recurred, immediate evaluation is warranted rather than waiting 7 days 2
- The persistence of symptoms beyond antibiotic treatment suggests either resistant bacterial infection or parasitic etiology 1
Common Pitfalls to Avoid
- Do not empirically treat without testing - empiric treatment of suspected recurrence without confirmatory testing is discouraged 3
- Do not use multiplex PCR panels alone - these detect DNA, not necessarily viable organisms, so clinical correlation is essential 1
- Do not forget travel history context - Mexico travel significantly increases risk for specific pathogens that require targeted testing 2, 1