My chrysosporium is a scedosporium


Department of Family Medicine, Aurora UW Medical Group, Center for Urban Population Health

Presentation Notes

Presented at 2013 Aurora Scientific Day, Milwaukee, WI


Background/significance: A mold which phenotypically resembles and has the same unusual ammonia tolerance as Blastomyces dermatitidis was previously isolated in-vitro from soil. It was tentatively identified as Chrysosporium zonatum.

Purpose: To positively identify and determine the ubiquity of this organism which may be pathogenic and share a microenvironment with B dermatitidis. Methods: The original isolate was identified by expert phenotypic analysis and internal transcribed spacer region rDNA (ITS) sequencing and BLAST search. 10 soil samples were obtained from a yard, park and riverbank in suburban Milwaukee County, November 5, 2012 (5.6 °), diluted two-fold in aqueous 0.5% allantoin, Tween-80 (20 ml/l) and penicillin/streptomycin and incubated at 37º. Three weeks later, samples were spread on low glucose, high (13.2 mM) ammonia basic salts agar plates at pH=7.5 at 37° in gas impermeable bags. New isolates were examined, and compared to the original isolate, on Sabouraud dextrose agar (SDA) at 20° and 37° for colony size, morphology and microscopic appearance.

Results: The original isolate was identified as Scedosporium apiospermum, a fungus associated with opportunistic, traumarelated and other human infections which has been isolated from feces, sewage, soil and other materials. A phenotypically similar strain was isolated from 3/4 samples from the yard (beneath the dryer vent that yielded the original isolate, under a woodpile and next to a sandbox). No colonies formed on plates from the other 7 samples.

Conclusion: Scedosporium apiospermum may compete with Blastomyces in high-ammonia environments, and may be specifically enriched by this 2-step soil isolation technique, suggesting the need for test modification to favor Blastomyces isolation. Ammonia tolerance may explain the finding of Scedosporium in feces and sewage.

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