Closing the diagnostic gap in medical mycology: The LODDY Test for identification of Lodderomyces elongisporus

Abstract

Lodderomyces elongisporus is an emerging, cryptic opportunistic yeast increasingly linked to fungemia, especially in immunocompromised patients and those with indwelling devices. Frequently misidentified as Candida parapsilosis due to phenotypic overlap, it escapes timely diagnosis, delaying effective therapy. Despite accounting for <2% of candidemia cases, true prevalence is likely underestimated. Critically, L. elongisporus exhibits reduced susceptibility to echinocandins, making misidentification clinically dangerous. To develop and validate the LODDY Test - a novel, cost-effective, pH-indicator-based culture medium for rapid, accurate identification of L. elongisporus, particularly in resource-limited settings. The LODDY Test integrates four differential carbohydrates (sucrose, maltose, lactose, and arabinose) with bromocresol purple. We tested 41 L. elongisporus isolates (1 reference, 40 internal transcribed spacer (ITS) region -confirmed environmental strains) and 40 comparator yeasts (C. parapsilosis sensu stricto, C. albicans, C. tropicalis, and Nakaseomyces glabratus) from urban/peri-urban Thai sites. Species identity was confirmed by ITS sequencing. LODDY results were benchmarked against the Analytical Profile Index 20C Auxanographic assimilation test (API 20C AUX), CHROMagar™ chromogenic medium, and Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS), and ITS-DNA sequencing. The LODDY Test achieved 100% sensitivity and specificity, distinctly identifying L. elongisporus (no color change) from yellow-producing Candida spp. and purple N. glabratus. Performance matched MALDI-TOF MS and ITS sequencing but required only basic equipment. The LODDY Test is a low-cost, high-accuracy diagnostic tool suitable for decentralized labs. Its clinical validation in bloodstream isolates is the next step toward improving candidemia outcomes in low-resource settings.