Correlation of Genotype and In Vitro Susceptibilities of Cryptococcus gattii Strains from the Pacific Northwest of the United States

Abstract

Cryptococcus gattii emerged in North America in 1999 as a human and veterinary pathogen on Vancouver Island, British Columbia. The emergent subtype, VGIIa, and the closely related subtype VGIIb can now be found in the United States in Washington, Oregon, and California. We performed multilocus sequence typing and antifungal susceptibility testing on 43 isolates of C. gattii from human patients in Oregon, Washington, California, and Idaho. In contrast to Vancouver Island, VGIIa was the most frequent but not the predominant subtype in the northwest United States. Antifungal susceptibility testing showed statistically significant differences in MICs between the subtypes. This is the first study to apply antifungal susceptibility testing to C. gattii isolates from the Pacific Northwest and the first to make direct comparisons between subtypes.

In vitro antifungal susceptibility profiles and genotypes of 308 clinical and environmental isolates of Cryptococcus neoformans var. grubii and Cryptococcus gattii serotype B from north-western India

“…grubii isolates. This is in agreement with the results of Iqbal et al (2010) (Scholer & Polak, 1984), which is comparable to our results of 1.2 % (2/162) for clinical C. neoformans var. grubii isolates.…”

Molecular typing and in vitro antifungal susceptibility of Cryptococcus spp from patients in Midwest Brazil

“…In Brazil, Souza et al [20] reported low MIC values for voriconazole and amphotericin B against isolates of C. gattii. It is worth highlighting that C. gattii VGIII was identified in this study and that the MIC values obtained for amphotericin B were low, in agreement with those in the literature [47,50,51], considering the cutoffs used by Nguyen and Yu [30] and Lozano-Chui et al [31]. For voriconazole, MIC values against C. gattii (range = 0.06 -0.5 mg/L were in agreement with those presented by Espinel-Ingroff et al [53], whereas against C. neoformans MIC values (range = 0.06-0.5 mg/L), were lower compared with those of the same study.…”

“…The majority of studies addressing in vitro susceptibility testing for amphotericin B against C. neoformans and C. gattii have shown that many of these isolates are susceptible at MIC values ≤ 1 mg/L [47,48,[50][51][52][53], similar to the MIC values obtained in this work. However, the literature reports MIC values for amphotericin B ≥ 1 µg/mL, such as Lozano-Chui et al [31], who reported MIC values of 3-4 mg/L, which were associated with treatment failure.…”

“…Studies conducted in several parts of the world have shown low MIC 50 and MIC 90 values for fluconazole against C. neoformans VNI [43][44][45]. In this study, the MIC 50 and MIC 90 values for fluconazole were 4-8 mg/L; however, higher values (2-128 mg/L) have been reported for isolates of C. neoformans VNI [46].…”

“…Iqbal et al [50] reported differences in the susceptibility profiles of the molecular types of C. gattii, having determined higher MIC values for the VGII subtypes than the VGI and VGIII subtypes. In Brazil, Souza et al [20] reported low MIC values for voriconazole and amphotericin B against isolates of C. gattii.…”