Answer to November 2013 Photo Quiz

Answer: Malassezia pachydermatis. Malassezia pachydermatis is a lipophilic yeast that is a common colonizer and pathogen on the skin surfaces of canines and their human caretakers (1). Because of the lipophilicity of Malassezia species, fungemia with these organisms, particularly Malassezia furfur, a human skin colonizer associated with pityriasis (tinea) versicolor, is highly associated with the use of lipid-containing total parenteral nutrition (TPN) (2). Yeasts in the genus Malassezia are urease positive, aerobic nonfermenters with an ideal growth temperature of 35 to 37°C. They require, with the exception of M. pachydermatis, lipid supplementation in media due to their complete inability to synthesize fatty acids. This patient presented with flu-like symptoms, and given her complicated medical history with methicillin-resistant Staphylococcus aureus (MRSA) bacteremia and enterocutaneous fistula, antibiotic therapy was initiated immediately. Laboratory testing of her vital signs on admission did not indicate that she was in or near septic shock, and although her maximum temperature spiked to 103°F on hospital day 1, her vital signs remained relatively stable throughout her stay. Her aerobic blood culture became positive for organisms with yeast morphologies after 72 h. The patient was started on micafungin at this time, and blood samples were cultured onto appropriate media. On Emmons Sabouraud dextrose agar, the colonies formed were yellow with a creamy texture, and on potato flake agar, the colonies were yellow-white and spiculated. A lipid supplement to the medium was not required for the organism to grow. A wet mount of these organisms showed round-to-oval organisms with monopolar broad-based budding and collarette formation, the characteristic morphology of M. pachydermatis. M. pachydermatis is rarely associated with fungemia and systemic infection, and the reported cases have occurred mainly in neonates and the immunocompromised (2, 3). While many individuals are likely carriers due to colonization of their canine pets, the yeast is rarely implicated in infections of otherwise healthy individuals (1). In this case, the patient's history of TPN administration, as well as ovarian cancer and multiple other comorbidities, certainly increased the risk of systemic infection due to M. pachydermatis fungemia. (See page 3475 in this issue [doi:10.1128/JCM.02293-12] for photo quiz case presentation.)