Update on antifungal resistance in Aspergillus and Candida

Conference report from the International Congress on Infectious Diseases 2014: Part One. 16th International Congress on Infectious Diseases, Cape Town, South Africa 2-5 April 2014

The 16th International Congress on Infectious Diseases (ICID) was held in Cape Town this year, marking the return of the conference to Africa for the first time in 22 years. While infectious diseases such as malaria, tuberculosis and HIV--all still prevalent in the African healthcare landscape--dominated the program, the conference featured several important sessions on fungal infection and a significant number of posters devoted to this critical medical area. Within the context of the rise of antimicrobial resistance, now identified by the WHO as one of the three greatest threats to human health, came the message that resistance is not limited to antimicrobials, but that antifungal resistance is also a significant and emerging threat worldwide.

Antifungal drug resistance in Candida species

Invasive Candida infections are well established infectious entities of immunocompromised or critically ill patients and are characterised by high morbidity and mortality. Owing to the common eukaryotic structure of fungi and humans, a limited number of antifungal drugs is available for therapeutic purposes. In this unsatisfactory scenario, the emergence of drug resistance represents an important health problem. Failure of antifungal treatment can be related to host factors, to the pharmacokinetic and pharmacodynamic parameters of the drug, or to morphological, reproductive modalities and biofilm production of the fungus itself. Innate or acquired antifungal resistance derives from the presence or onset of molecular mechanisms related to the toxic activity of the drug itself. The resulting resistance can thus be extended to different molecules of the same class according to a greater or lesser affinity of the molecules for the target. In addition, non-specific cellular mechanisms of extrusion of toxic substances, such as overexpression of efflux pumps, can play a role involving different antifungal classes. Here we briefly review the current antifungal susceptibility testing methods and their usefulness as predictors of antifungal resistance in Candida spp., focusing on assessment of the involved molecular mechanisms.