Acquired multi-azole resistance in Candida tropicalis during persistent urinary tract infection in a dog

• Azole resistance acquisition by Candida tropicalis is reported.
• Studied isolates came from a dog with persistent urinary candidiasis.
• Pre- and post-antifungal treatment isolates were clonally related.
• A novel frameshift mutation in the ERG3 gene was found in post-treatment isolates.

Multi-azole resistance acquisition by Candida tropicalis after prolonged antifungal therapy in a dog with urinary candidiasis is reported. Pre- and post-azole treatment isolates were clonally related and had identical silent mutations in the ERG11 gene, but the latter displayed increased azole minimum inhibitory concentrations. A novel frameshift mutation in ERG3 was found in some isolates recovered after resistance development, so it appears unlikely that this mutation is responsible for multi-azole resistance.