Dual-antibiotic MAC (DAM) medium: A simple Candida auris screening medium suitable for routine laboratories

Abstract Candida auris is an emerging multidrug-resistant pathogen responsible for hospital outbreaks, and its screening remains difficult for routine laboratories. We modified MacConkey (MAC) agar by adding gentamicin and chloramphenicol, based on the Specific Candida auris (SCA) medium formula, to create a selective dual-antibiotic MAC (DAM) medium. DAM was tested against six ATCC Candida strains, three C. auris isolates (Clades I–Ⅲ), and eight carbapenem-resistant Gram-negative bacilli strains, then validated with 130 clinical samples. Conventional MAC and Sabouraud dextrose agar served as controls, and SCA medium was used as the sole comparator because CHROMagar™ Candida Plus is unavailable in China. C. auris grew freely on DAM, whereas other Candida species were inhibited. Among 130 clinical samples, 49 were confirmed positive for C. auris by MALDI-TOF mass spectrometry. At 40°C, DAM recovered all 49 isolates, which were subsequently confirmed as C. auris by MALDI-TOF MS (sensitivity 100%, 95% CI: 92.7%–100%; specificity 100%, 95% CI: 95.5%–100%), whereas at 35°C, 43 isolates were recovered (sensitivity 87.8%, 95% CI: 75.8%–94.3%). The bacterial contamination rate on DAM at 40°C (26.9%) was significantly lower than at 35°C (33.1%, P = 0.013) and lower than on SDA (51.5%) and MAC (68.5%) (P < 0.001 for both). DAM costs approximately 1.7 RMB per plate and can be stored at 4°C for up to 30 days. In conclusion, DAM is a sensitive, rapid, low-cost, and accessible medium showing promising proof-of-concept performance for C. auris screening. Given the limited sample size, unbalanced specimen distribution, and absence of direct comparison with CHROMagar Candida Plus, further multicenter validation is warranted before routine implementation.