A case of Magnusiomyces capitatus isolated during monitoring in an antimicrobial diagnostic stewardship context.

Magnusiomyces capitatus (M. capitatus) is an emerging opportunistic yeast in the Mediterranean region typically isolated from immunocompromised patients, usually affected by blood malignancies. We reported a rare case of M. capitatus infection, isolated from a drainage fluid in a patient affected by lung cancer recovered in the University Hospital of Campania "Luigi Vanvitelli", Naples, Italy. The isolate was identified by phenotypic methods, i.e., Gram and Lactophenol cotton blue (LCB) staining, and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) analysis. We identified M. capitatus on the third day from Sabouraud Dextrose Agar supplemented with chloramphenicol and gentamicin. Antifungal susceptibility test revealed that 5-fluorocytosine was the most active drug against M. capitatus , followed by itraconazole and voriconazole, micafungin, amphotericin B and fluconazole, posaconazole, anidulafungin, and caspofungin. Our data showed the importance of an early cultural and fast microbiology diagnosis based on the characteristic morphologic features observed in Gram-stained smears of blood culture positive bottles, and the validation via MALDI-TOF MS. This dual approach has significant impact in the clinical management of infectious diseases and antibiotic stewardship, by integrating sample processing, fluid handling, and detection for rapid bacterial diagnosis.