Abstract
We report the first molecularly confirmed, genetically sequenced, and phylogenetically traced case of locally acquired Cyclospora cayetanensis infection in Italy. Earlier Italian reports described clinical cases of cyclosporiasis. However, sequence-based molecular confirmation and phylogenetic traceability were not available. An 86-year-old Italian woman with no recent travel history developed diarrhea during hospitalization. Routine microbiological investigations were negative, whereas multiplex real-time PCR detected C. cayetanensis. The diagnosis was confirmed by amplification and Sanger sequencing of the 18S rRNA gene. Phylogenetic analysis demonstrated that the Italian isolate clustered with strains associated with outbreaks linked to tropical and subtropical regions, suggesting a probable imported foodborne origin. Although cyclosporiasis is generally self-limiting, infection in frail elderly patients with multiple comorbidities may contribute to clinical deterioration. Diarrheal symptoms resolved after antimicrobial therapy, but the patient subsequently died due to pulmonary edema. While a direct causal relationship cannot be established, extra-intestinal involvement has been reported. This case highlights the importance of molecular diagnostics and phylogenetic analysis in non-endemic settings to improve surveillance and source attribution of C. cayetanensis infection.