Problems in Antifungal Susceptibility Testing

Vladimír Buchta¹ (buchta@faf.cuni.cz), Miloš Otčenášek²

¹Department of Biological and Medical Sciences, Faculty of Pharmacy, Charles University, Heyrovského 1203, 501 65 Hradec Králové
²Institute of Experimental Biopharmaceutics, Joint Scientific Center of Czech Academy of Sciences and PRO.MED. CS, Heyrovského 1207, 500 02 Hradec Králové, Czech Republic

Summary

There has been a surge in the importance of in vitro antifungal susceptibility testing during the last twenty years. This results from the increasing incidence of fungal infections and the development of new antimycotic drugs. The tests are a part of the screening and evaluation of compounds of potential interest. At a clinical level, in vitro tests enable the monitoring of the concentrations of antifungals in body fluids and can provide clinicians with useful information that would facilitate the choice of an appropriate therapeutic regimen for the treatment of mycoses. Unfortunately, most of the methods are unstandardised and give results that are not always reliable in the prediction of a clinical response. Problems of the standardisation and reproducibility of antifungal susceptibility tests arise from a number of factors affecting the test results. The main sources of discrepancies between in vitro and in vivo results are inadequate in vitro test systems; the pharmacological profile of the antifungal drug in question; the immunological status of the patient in question; and the exertion of subinhibitory concentrations of some antimycotics on pathogenic fungi, including their interference with fungal virulence mechanisms. Currently used methods are presented and discussed with emphasis on interpretation and clinical relevance of in vitro test results.