Moulds are only rarely recovered from blood cultures and when seen, may have an atypical appearance. However in this setting misidentification can have particularly important clinical consequences, potentially leading to inappropriate treatment.
We describe a positive blood culture from an immune-compromised patient whose initial Gram stain showed fungal hyphae. After 24-hours incubation the organism was growing on Sabdex and Candida CHROM media. Examination of the organism showed an elongated yeast cell whose appearance on the chromogenic agar was typical of C. albicans. Initially this isolate was reported as a probable Trichosporon species as arthroconidia were present by day 3 and urease activity had been demonstrated. Upon further workup an ID32C panel gave no identification and the biochemical pattern seen was not consistent with a Trichosporon species.
18S ribosomal gene sequencing gave an identification of Debaryomyces hansenii which was also inconsistent with the phenotypic findings. The identification remained elusive until 3 weeks later when Sabdex plates left at room temperature were observed to have a powdery, cream-tan mould-like isolate with mycelia and branching chains of arthroconidia typical of Arthrographis kalrae.
This case illustrates some of the difficulties of identifying even common moulds when recovered from blood cultures. Even molecular techniques may not provide sufficient information to provide a definitive genus level identification.