Candida auris is a recently emerged global fungal pathogen, which causes life-threatening infections, often in healthcare settings. C. auris infections are worrisome because the fungus is often resistant to multiple antifungal drug classes. Furthermore, C. auris forms durable and difficult to remove biofilms. Due to the relatively recent, resilient, and resistant nature of C. auris, we investigated whether it produces the common fungal virulence factor melanin. Melanin is a black-brown pigment typically produced following enzymatic oxidation of aromatic precursors, which promotes fungal virulence through oxidative stress resistance, mammalian immune response evasion, and antifungal peptide and pharmaceutical inactivation. We found that certain strains of C. auris oxidized L-DOPA and catecholamines into melanin. Melanization occurred extracellularly in a process mediated by alkalinization of the extracellular environment, resulting in granule-like structures that adhere to the fungus’ external surface. C. auris had relatively high cell surface hydrophobicity, but there was no correlation between hydrophobicity and melanization. Melanin protected the fungus from oxidative damage, but we did not observe a protective role during infection of macrophages or Galleria mellonella larvae. In summary, C. auris alkalinizes the extracellular medium, which promotes the non-enzymatic oxidation of L-DOPA to melanin that attaches to its surface, thus illustrating a novel mechanism for fungal melanization.

Background: Obtaining respiratory samples to diagnose tuberculosis in young children is challenging. Oral swabs are alternative noninvasive specimens for microbiology. Methods: We conducted an interim prospective diagnostic accuracy evaluation of Xpert MTB/RIF Ultra (Ultra) on oral swabs for pulmonary tuberculosis in children aged <5 years in Uganda. Most children had 2 consecutive swabs collected in a single cryovial (double swabs). Reference tests consisted of Ultra and culture on 2 nasopharyngeal aspirates and 1 gastric aspirate and Ultra on 1 stool. Children were classified as having confirmed tuberculosis, unconfirmed tuberculosis, or unlikely tuberculosis per the National Institutes of Health. Diagnostic accuracy was determined against a microbiological reference standard and a composite reference standard. Results: From August 2021 to February 2024, 444 children were enrolled, of whom 399 had complete classifications: 33 had confirmed tuberculosis, 269 had unconfirmed tuberculosis, 70 had unlikely tuberculosis, and 27 were unclassifiable. The median age was 16 months and 17% had HIV. Most children (398/399) had oral swabs collected, all with conclusive Ultra results. The sensitivity of double swabs was 6.9% with a microbiological reference standard (95% CI, 1.9%–22.0%) and 1.8% with a composite reference standard (95% CI, .8%–4.1%). Specificity was at least 99%. Swabs detected tuberculosis in 4 children with negative reference test results, of whom 3 had unconfirmed tuberculosis. Conclusions: The low sensitivity of Ultra on double swabs precludes its role as a principal diagnostic approach in young children. However, detection of tuberculosis in children who were not otherwise microbiologically diagnosed suggests the utility of oral swabs as add-on samples to increase yield.

Candida auris is a recently emerged global fungal pathogen, which causes life-threatening infections, often in healthcare settings. C. auris infections are worrisome because the fungus is often resistant to multiple antifungal drug classes. Furthermore, C. auris forms durable and difficult to remove biofilms. Due to the relatively recent, resilient, and resistant nature of C. auris , we investigated whether it produces the common fungal virulence factor melanin. Melanin is a black-brown pigment typically produced following enzymatic oxidation of aromatic precursors, which promotes fungal virulence through oxidative stress resistance, mammalian immune response evasion, and antifungal peptide and pharmaceutical inactivation. We found that certain strains of C. auris oxidized L-DOPA and catecholamines into melanin. Melanization occurred extracellularly in a process mediated by alkalinization of the extracellular environment, resulting in granule-like structures that adhere to the fungus external surface. C. auris had relatively high cell surface hydrophobicity, but there was no correlation between hydrophobicity and melanization. Melanin protected the fungus from oxidative damage, but we did not observe a protective role during infection of macrophages or Galleria mellonella larvae. In summary, C. auris alkalinizes the extracellular medium, which promotes the non-enzymatic oxidation of L-DOPA to melanin that attaches to its surface, thus illustrating a novel mechanism for fungal melanization.