Cyclospora cayetanensis Diarrhea Mimicking Enteric Fever: A Diagnostic Stewardship Case Report

Cyclospora cayetanensis is an underrecognized cause of prolonged diarrheal illness in endemic regions and is frequently misdiagnosed as enteric fever or amoebiasis, resulting in inappropriate antimicrobial use. We report the case of chronic small bowel diarrhea in an immunocompetent adult following ingestion of contaminated water, who was initially treated with multiple empiric antibiotic regimens without sustained clinical improvement. Owing to the protracted course, normal leukocyte counts, and failure to respond to antibacterial therapy, targeted gastrointestinal molecular testing and modified acid-fast staining were pursued, leading to the diagnosis of C . cayetanensis infection. Treatment with trimethoprim–sulfamethoxazole resulted in rapid clinical resolution. This case underscores the importance of early clinical suspicion, appropriate stool-based diagnostics, and diagnostic stewardship in preventing unnecessary antimicrobial exposure and improving the patient outcomes.