The importance of susceptibility testing

Abstract number: 1133_237

Johnson E.M.

Whilst antifungal drug resistance has not proved to be as problematic as that experienced with antibacterial agents, both intrinsic and emergent resistance are encountered and antifungal susceptibility testing can help in the guidance of prescribing practices. The expanding armamentarium of antifungal agents dictates that the clinician has some guidance in selecting the most appropriate agent for a particular infection and relative susceptibility of the infecting organism is an important factor in the decision. There are many test parameters that can potentially impact on the susceptibility test result and in the early years of testing differences in test methods produced confusing and conflicting results. In recent years standardized methods for susceptibility testing of yeast and mould isolates have been introduced and for some drugs it has been possible to define breakpoints. Whilst there are still certain reservations over the test methods and their application to certain organism-drug combinations, their widespread adoption makes national and international comparisons of susceptibility trends possible. Intrinsic resistance, which is generally consistent and predictable, is encountered in an increasing number of yeast and mould species and highlights the need for accurate speciation of infecting organisms. Susceptibility testing is of great importance in detecting intrinsic resistance in a species and therefore establishing the spectrum of activity of new and developmental agents. There is the possibility that general use of an agent will lead to the development of emergent resistance in a previously susceptible organism. Currently there are few problems with emergent resistance during a course of treatment which is potentially a more serious scenario than the more predictable innate resistance. Far more likely to occur in yeast rather than mould infections, this has been encountered predominantly with flucytosine and fluconazole mainly as a consequence of inappropriate prescribing practices for specific infections in certain patient groups. It is therefore important that testing mechanisms are introduced with the capacity to identify potential problems as they occur.

Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Location: Oxford, UK
Presentation type:
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