Silent Outbreaks of Candida duobushaemulonii in a Pediatric Ward in Brazil

<b>Background</b>: While <i>Candida auris</i> is well known to cause hospital outbreaks, other species in the <i>C. haemulonii</i> complex are less well documented but gained attention as opportunistic pathogens. Only one documented outbreak has been published. We describe the second, silent, fungemia outbreak due to antifungal-susceptible <i>C. duobushaemulonii</i>. <b>Methods</b>: We retrospectively genotyped six <i>C. duobushaemulonii</i> bloodstream isolates, collected in a 4-month-period in 2022 (n = 4) and during a week in 2024 (n = 2) in pediatric patients in Brazil. Whole genome sequencing (WGS) was done and compared to n = 33 publicly available genomes, including four cases from an outbreak in Panama. Antifungal susceptibility was performed with the reference CLSI method. <b>Results</b>: MALDI-TOF-MS identified isolates as either <i>C. pseudohaemulonii</i> or <i>C. duobushaemulonii</i> albeit with low scores. ITS sequence analyses confirmed all isolates as <i>C. duobushaemulonii</i>. WGS proved the presence of an outbreak among four pediatric patients in 2022 and a genetically distinct cluster of two cases in 2024. All six isolates were susceptible to azoles and echinocandins and were interpreted as being resistant to amphotericin B with a MIC at breakpoint of 2 µg/mL. <b>Conclusions</b>: This study describes the second documented outbreak due to the rare yeast <i>C. duobushaemulonii</i>, belonging to the <i>C. haemulonii</i> species complex, during 2022-2024 in patients admitted to a pediatric oncology ward in a Brazilian hospital.