Whole genome analysis of azole-resistant Candida tropicalis candidemia outbreak in a haematology ward: A single centre experience

The emergence of azole-resistant Candida tropicalis poses a significant threat in healthcare settings. It contributed to high morbidity and mortality, particularly in those undergoing chemotherapy for haematological diseases. In this study, we investigated a suspected outbreak in the haematology ward of Hospital Sultanah Bahiyah involving three patients, using whole genome sequencing. Azole-resistant C. tropicalis was isolated from all patients during episodes of neutropenic sepsis following chemotherapy. The index patient developed breakthrough candidemia while receiving fluconazole prophylaxis. Subsequently, the second and third patients developed candidemia occurring four days apart. Consequently, phylogenetic analysis confirmed that these isolates formed a clade closely related to other C. tropicalis strains, indicating a clonal nosocomial transmission. Further analysis demonstrated that, among key azole resistance genes, mutations were specifically identified in ERG11. Our findings underscore the critical role of genomic surveillance in uncovering transmission chains of multidrug-resistant fungal pathogens and highlight an urgent need for reinforced infection control measures to contain the spread of this clone.