Preliminary evaluation of the performance of CHROMagar™ C.neoformans medium for the presumptive identification of the Cryptococcus neoformans/C. gattii species complex isolates.

Identifying fungal species from cultures remains a significant challenge for clinical labs in resource-limited settings. Here we evaluated the performance of the CHROMagar™ C.neoformans (X136) medium for the presumptive identification of Cryptococcus neoformans/C. gattii isolates. The color and appearance of the colonies of 53 yeast isolates, whose characteristics are well established using reference methods (genomic and proteomic methods) were analyzed. These isolates included: 36 C. neoformans/C. gattii (33 C. neoformans and 3 C. gattii), 5 non-neoformans/non-gattii Cryptococcus (4 Cutaneotrichosporon curvatus formerly Cryptococcus curvatus and 1 Papiliotrema laurentii=Cryptococcus laurentii), 11 Candida spp. (7 Candida albicans, 3 C. tropicalis, and 1 C. parapsilosis), and 1 Rhodotorula spp. The overall agreement between the presumptive identification of C. neoformans/C. gattii using CHROMagar™ C.neoformans (X136) and the reference identification methods was estimated at 88.7% (47/53; 95% CI, 79.2-96.2), with a substantial Cohen's kappa coefficient (κ=0.755; 95% CI, 0.555-0.921; p < 0.001). Sensitivity and specificity were estimated at 86.1% and 94.1%, respectively. Furthermore, it was not possible to distinguish colonies of C. neoformans from those of C. gattii, as all were roughly and presumptively identified as C. neoformans. The acceptable performance of CHROMagar™ C.neoformans (X136) in identifying C. neoformans/C. gattii among yeast isolates offers promising prospects for its use in routine clinical practice; particularly in resource-limited settings, as a complement to other usual methods (cryptococcal antigen test, carbohydrate assimilation tests, India ink staining, etc.). Further evaluations using a larger and more diverse fungal isolates and clinical samples are strongly recommended.