Comparative antifungal susceptibility analyses of Cryptococcus neoformans VNI and Cryptococcus gattii VGII from the Brazilian Amazon Region by the Etest, Vitek 2, and the Clinical and Laboratory Standards Institute broth microdilution methods

Abstract

Early diagnosis, efficient clinical support, and proper antifungal therapy are essential to reduce death and sequels caused by cryptococcosis. The emergence of resistance to the antifungal drugs commonly used for cryptococcosis treatment is an important issue of concern. Thus, the in vitro antifungal susceptibility of clinical strains from northern Brazil, including C. neoformans VNI (n = 62) and C. gattii VGII (n = 37), to amphotericin B (AMB), 5-flucytosine, fluconazole, voriconazole, and itraconazole was evaluated using the Etest and Vitek 2 systems and the standardized broth microdilution (CLSI-BMD) methodology. According to the CLSI-BMD, the most active in vitro azole was voriconazole (C. neoformans VNI modal MIC of 0.06 μg/ml and C. gattii VGII modal MIC of 0.25 μg/ml), and fluconazole was the least active (modal MIC of 4 μg/ml for both fungi). Modal MICs for amphotericin B were 1 μg/ml for both fungi. In general, good essential agreement (EA) values were observed between the methods. However, AMB presented the lowest EA between CLSI-BMD and Etest for C. neoformans VNI and C. gattii VGII (1.6% and 2.56%, respectively, P < .05 for both). Considering the proposed Cryptococcus spp. epidemiological cutoff values, more than 97% of the studied isolates were categorized as wild-type for the azoles. However, the high frequency of C. neoformans VNI isolates in the population described here that displayed non-wild-type susceptibility to AMB is noteworthy. Epidemiological surveillance of the antifungal resistance of cryptococcal strains is relevant due to the potential burden and the high lethality of cryptococcal meningitis in the Amazon region.

Epidemiological and Clinical Characteristics, Antifungal Susceptibility, and MLST-Based Genetic Analysis of Cryptococcus Isolates in Southern Taiwan in 2013–2020

“…The environmental triazole (tebuconazole) used as an agrochemical pesticide may induce cross-resistance to clinically available azoles in C. neoformans and C. gattii [ 16 ]. Moreover, it is noteworthy that a high frequency of C. neoformans isolates with non-wild-type (non-WT) susceptibility to AMB has been reported [ 17 , 18 ]. However, routine antifungal susceptibility testing (AST) is not performed in most microbiological laboratories.…”

Early clinical and microbiological predictors of outcome in hospitalized patients with cryptococcal meningitis

“…The major agents of cryptococcosis are members of C. neoformans and C. gattii complex. This complex was recognized in 2015 into seven species, based on phenotypic and genotypic, geographic, epidemiological and virulence characteristics [8][9][10][11][12][13][14][15]. The new classification includes the species C. neoformans sensu strictu (s.s) (genotype VNI/VNII/VNB), hybrids between C. neoformans and C. deneoformans (genotype VNIII) and C. deneoformans (genotype VNIV), and C. gattii complex is formed by C. gattii s.s (VGI), C. deuterogattii (VGII), C. bacillisporus (VGIII), C. tetragattii (VGIV), and C. decagattii (VGIIIc/ VGIV) [8,16].…”

Molecular identification and antifungal susceptibility testing of Pucciniomycotina red yeast clinical isolates from Rio de Janeiro, Brazil

“…Gradient diffusion methods are usually used as its substitute due to the easiness in performance and in the determination of MIC values. The usefulness of gradient diffusion methods is already described for Candida and Cryptococcus species [18,19], but for other fungi, the gradient diffusion MICs do not correlate with the gold standard method [20]. This study has shown that Etest® can be a fast and reliable methodology for the MIC v al u e s' d e t e r m i n a t i o n of a m p h o t e r i c i n B a n d voriconazole against R. mucilaginosa and thus, it could be applied to a diagnosis laboratory routine as well as to the epidemiological resistance surveillance.…”