Increased Antifungal Drug Resistance in Clinical Isolates of Cryptococcus neoformans in Uganda

Abstract

iCryptococcal antigen screening is recommended among people living with AIDS when entering HIV care with a CD4 count of <100 cells/l, and preemptive fluconazole monotherapy treatment is recommended for those with subclinical cryptococcal antigenemia. Yet, knowledge is limited of current antimicrobial resistance in Africa. We examined antifungal drug susceptibility in 198 clinical isolates collected from Kampala, Uganda, between 2010 and 2014 using the CLSI broth microdilution assay. In comparison with two previous studies from 1998 to 1999 that reported an MIC 50 of 4 g/ml and an MIC 90 of 8 g/ml prior to widespread human fluconazole and agricultural azole fungicide usage, we report an upward shift in the fluconazole MIC 50 to 8 g/ml and an MIC 90 value of 32 g/ml, with 31% of isolates with a fluconazole MIC of >16 g/ml. We observed an amphotericin B MIC 50 of 0.5 g/ml and an MIC 90 of 1 g/ml, of which 99.5% of isolates (197 of 198 isolates) were still susceptible. No correlation between MIC and clinical outcome was observed in the context of amphotericin B and fluconazole combination induction therapy. We also analyzed Cryptococcus susceptibility to sertraline, with an MIC 50 of 4 g/ml, suggesting that sertraline is a promising oral, low-cost, available, novel medication and a possible alternative to fluconazole. Although the CLSI broth microdilution assay is ideal to standardize results, limit human bias, and increase assay capacity, such assays are often inaccessible in low-income countries. Thus, we also developed and validated an assay that could easily be implemented in a resource-limited setting, with similar susceptibility results (P ‫؍‬ 0.52).

Identification of cyclosporin C from Amphichorda felina using a Cryptococcus neoformans differential temperature sensitivity assay

“…Current therapies for this disease include a limited number of antifungal agents (amphotericin B, flucytosine, and fluconazole). Despite the emergence of drug-resistant strains (Smith et al 2015), no new therapies for this condition have been introduced in the past few decades (Coelho and Casadevall 2016; Perfect 2017). …”

IP3-4kinase Arg1 regulates cell wall homeostasis and surface architecture to promoteCryptococcus neoformansinfection in a mouse model

“…Amphotericin B exhibits significant haematological and nephrological toxicity 4 , while echinocandins are ineffective against the Cryptococcus complex 5,6 . Furthermore, fluconazole-resistant C. neoformans has been reported in Sub-Saharan Africa and South East Asia 7,8 . A detailed understanding of the biology of C. neoformans and other pathogenic fungi is essential for the identification of new drug targets.…”

The antifungal pipeline: a reality check

“…Fourth, it is important to have an optimized combination of therapeutic agents or classes to increase potency and reduce the emergence of drug resistance. Fifth, resistant strains are increasing in number for some antifungal agent classes, particularly for the azoles and the echinocandins 13 . Sixth, safety remains a very important issue for antifungal drug use.…”