A rare case of <i>Trichosporon inkin</i> bloodstream infection in an immunocompetent patient: Diagnostic challenges and antigenic cross-reactivity

<p xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" dir="auto" id="d6664000e99"> <i>Trichosporon inkin</i> is a rare opportunistic pathogen typically associated with superficial infections but can also cause invasive infections, particularly in immunocompromised hosts. Here, we report a rare case of <i>T. inkin</i> bloodstream infection in an immunocompetent male with a history of cerebral hemorrhage surgery. The patient presented with fever, limb twitching, and brain lesions. Blood cultures revealed fungal growth, which was initially misidentified as <i>Trichosporon ovoides</i> by mass spectrometry but was later confirmed as <i>T. inkin</i> through ITS and IGS1 sequencing. The isolate exhibited low MICs for azoles and amphotericin B but high MICs for echinocandins. Notably, the patient’s serum tested positive for cryptococcal antigen and <i>Aspergillus</i> galactomannan, despite the absence of clinical signs of cryptococcosis or aspergillosis. The <i>T. inkin</i> isolate expresses cryptococcal antigen but not galactomannan cross-reactive antigens when cultured in standard media. However, it expresses galactomannan cross-reactive antigens when cultured in human whole blood. This case highlights diagnostic challenges, including antigenic cross-reactivity and misidentification, and emphasizes the role of host-pathogen interactions in antigen expression. Our findings underscore the need for improved diagnostics and cautious interpretation of fungal antigen tests. This report expands the understanding of <i>T. inkin</i> infections and provides insights into their clinical management. </p>