Pythiosis: Case report leading to new features in clinical and diagnostic management of this fungal-like infection

Abstract

A 21-year-old man developed infectious keratitis after swimming in Spain whilst wearing contact lenses. Mycelial growth from a corneal sample suggested keratomycosis, but a drastic worsening of the patient’s condition was observed on antifungal drugs. On day 38, panfungal PCR identified Pythium insidiosum, which is an aquatic organism belonging to the oomycete family. Based on the recent literature, this patient was promptly prescribed a systemic and local antibiotic regimen and cure was ultimately achieved. In order to facilitate P. insidiosum identification in future cases, we have generated the first matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) reference spectrum for P. insidiosum. It is planned to deposit this MALDI-TOF MS reference spectrum on an open-access platform and this should allow immediate identification of the pathogen. Finally, this case report also demonstrates that P. insidiosum is emerging outside tropical and subtropical areas. Clinicians and microbiologists should have better knowledge to accurately manage and diagnose this sight-threatening infection. Keywords: Pythiosis, Pythium insidiosum, Keratitis, Panfungal PCR, MALDI-TOF mass spectrometry