Carbon assimilation profiles as a tool for Zygomycetes species identification

Abstract number: p1211

Schwarz  P., Lortholary  O., Dromer  F., Dannaoui  E.

Objectives: 

Identification of Zygomycetes to the genus and/or species level remains difficult by standard mycological procedures. The aim of this study was to evaluate carbon assimilation profiles as a tool for identification of the most common Zygomycetes responsible for infections in humans.

Methods: 

ID32C yeast identification system was used. Strips were inoculated by spore suspensions of 47 well-characterized isolates belonging to 8 Zygomycetes species (15 Rhizopus oryzae, 8 Absidia corymbifera, 7 Mucor circinelloides, 7 Rhizomucor pusillus, 4 Rhizopus microsporus, 3 Syncephalastrumracemosum, 2 Mucor indicus and 1 Cunninghamella bertholletiae). Strips were incubated at 28°C and were read visually after 72 hours of incubation.

Results: 

Overall seventeen carbon sources were useful for discriminating among the examined Zygomycetes species. The assimilation of the majority of carbon sources was homogeneous within a given species and heterogeneous between species. Each species showed a specific carbon assimilation profile allowing accurate identification except for M. circinelloides and M. indicus that shared similar profiles.

Table 1. Percentage of positive assimilation results for the most useful carbon sources

Conclusions: 

These results demonstrate that diagnosis of the main pathogenic Zygomycetes to the genus and species level is possible based on their carbon assimilation profiles. This technique using a commercially available system provides a fast and easy tool for identification of the most common Zygomycetes species.