First Isolation of Azole-Resistant Cryptococcus neoformans from Feline Cryptococcosis

Abstract

We report here, to the best of our knowledge, the first description of an in vitro fluconazole (FLZ)-resistant Cryptococcus neoformans var. grubii from a case of feline cryptococcosis. In vitro testing demonstrated that this isolate was resistant to FLZ (minimum inhibitory concentration, MIC, of 128 μg/ml) but remained susceptible to amphotericin B (0.064 µg/ml), itraconazole (0.38 µg/ml), voriconazole (0.023 µg/ml), and posaconazole (0.125 µg/ml). The predicted amino acid sequence of the lanosterol 14-α demethylase (ERG11) protein in the isolate was identical to that of the C. neoformans var. grubii reference strain, indicating that resistance was not mediated by mutation of the target gene's open reading frame. The RT-qPCR analysis for ERG11 and ATP-binding cassette (ABC) transporter-encoding gene (AFR1) indicated that the isolate increased transcription factor function of ERG11 and AFR1 than that of FLZ-susceptive strains. This observation, in combination with the lack of resistance to other azoles (that is, lack of crossresistance), suggests that resistance in our isolate was the result of overexpression of the endogenous ERG11 and ABC transporter.

Sterol 14α-Demethylase Ligand-Binding Pocket-Mediated Acquired and Intrinsic Azole Resistance in Fungal Pathogens

“…The azoles are used extensively because they are significantly less expensive than other antifungal treatments and their overall antimycotic activity is relatively broad spectrum [6]. Azole drugs are used in: (1) treatment and prophylaxis of livestock (e.g., ringworm in cattle, aspergillosis in poultry, oomycete infections in aquaculture [7][8][9][10], (2) treatment in veterinary medicine (e.g., pets and zoo animals) [11,12], (3) crop protection (e.g., mildews and rusts of grains, fruits, vegetables), (4) plant protection (e.g., leaf spot on flowers, scrubs and trees, including the timber industry) [4], (5) protection of buildings (e.g., antifouling coatings) [13], (f) cosmetic and hygiene products [14], and (6) prophylaxis and treatment in medicine [15].…”

Feline cutaneous nodular and ocular Cryptococcus neoformans in Belgium

“…5,24,32 Fluconazole is usually indicated for localised disease, 5 but some cryptococcal isolates have shown resistance with this drug. [33][34][35] Ketoconazole is a good choice for localised disease; however, it has more adverse effects than itraconazole. 4 Anorexia and weight loss have been reported in cats treated with ketoconazole after inoculation with C neoformans.…”

Antifungal Susceptibility of Clinical Isolates and Artificially Produced Multi-azole-resistant Strains of <i>Cryptococcus neoformans</i> (formerly: <i>Cryptococcus grubii</i>) to Ravuconazole

“…Cryptococcosis is a common cause of systemic mycoses in cats and of zoonotic fungal infections 1,2) . Feline cryptococcosis in Japan is typically attributed to Cryptococcus neoformans (former name; Cryptococcus grubii) [3][4][5][6] . Feline cryptococcosis is generally treated with azoles, such as fluconazole (FLCZ) and itraconazole (ITCZ), which are effective against human and animal cryptococcoses and have few side effects 1,2) .…”

“…FLCZ resistance, however, has been reported in isolates from human cryptococcoses [7][8][9] . Moreover, we have also described the first case of feline cryptococcosis in which an FLCZ-resistant C. neoformans strain was isolated from a cat 6) . Subsequent work demonstrated that multi-azole-resistant strains can readily be isolated from FLCZ-resistant strains by culturing in medium containing voriconazole (VRCZ) 10) .…”

“…We therefore believe that RVCZ will become the primary antifungal agent for treating human and animal cryptococcosis. 6) d These strains were obtained by culturing in medium containing voriconazole 10) .…”