1. Is azole resistance increasing amongst Aspergillus species?
Lass-Flörl Cornelia
Innsbruck Medical University
Divison of Hygiene and Medical Microbiology

2. Innsbruck Medical University

3. Faculty disclosure
Invited speaker: Pfizer, Gilead, MSD, Schering-Plough
Consultant: Pfizer, Gilead, Schering-Plough
Research Grants: Pfizer, Gilead, Schering-Plough

4. To determine the susceptibility of fungi to antifungal agents
Concentration that inhibits the growth of fungi = Minimum inhibitory concentration (expressed as µg/ml) Several methods can be used to define the MIC MIC reading = depends on the method used (EUCAST, CLSI, E-test,…)

6. MICs defined via E-test
Growth of fungus
MIC= zone of inhibition

7. Susceptibility testing: The big gaps
MICs help, but hard to standardize
Correlations appear possible based on individual isolates. Broad correlations based on multiple isolates are still lacking
Understanding this helps a lot when trying to correlate outcome with MIC
- Some patients get better despite MICs
- Some patients just don’t get better despite MICs
No rule when it correlates/not correlates
Rex, 2005

8. Facing In Vitro/In Vivo Correlation with Fungi
Aspergillus terreus
Amphotericin B
Intrinsic
Candida glabrata
Azoles
Intrinsic and acquired
Candida krusei
Candida lusitaniae
Histoplasma capsulatum
Fluconazole
Acquired
Has Antifungal Susceptibility Testing Come of Age?
Pfaller, Rex 2002

10. In vitro Azole-Resistance Differences within the world!
1997: first published case of ITC-resistant isolates of A. fumigatus (UK)
2000: 4.2% with higher MICs to ITC (>8 µg/ml) in a surveillance study (UK)
: 0.3% in the Netherlands
2000: 2.5%; 2002: 4.9%; 2006: 6.6% (NL)
2006: 2% in Spain
2007: 0% in Austria
Lass-Flörl, 2009

11. In vivo resistance
2002 first cases of what appears to be multiple-azole resistant in A. fumigatus
In vitro and in vivo correlations
Treatment: polyene or candine or azoles!
Reports derive from UK and The Netherlands
Denning 1997, Verweij, 1998, Moore 2001, Howard, 2006

12. Multiple-triazole-resistant aspergillosis.
Verweij PE, Mellado E, Melchers WJ
N Engl J Med (14):

13. Lass-Flörl, 2009

14. Frequency doese increase in some centres!
Resistance of A. fumigatus clinical isolates to triazoles (ITC, VOR, POS) has been reported with increasing frequency,
although it is generally considered an uncommon phenomenon.

15. Azoles: Voriconazole, Posaconazole, Itraconazole
Ergosterol
14-α-sterol demethylase
Lanosterol

16. Azole Resistance Mechanisms
Altered drug uptake
Increased drug efflux
1. Changes in drug import/export
cyp 51A
cyp 51A
2. Alterations in sterol biosynthesis
cyp 51A
cyp 51A
Overexpression of
drug target
Mutations in
cyp51A

17. AZOLE RESISTANT ASPERGILLUS FUMIGATUS

18. Mellado (2004,2005, 2007), Verweij 2007, Snelders 2009

19. Defintions: Azole- Resistance
Azole:a single drug resistance (ITC and VOR > 4µg/ml, POS > 2µg/ml)
Multi-azole resistance: resistant against at least two or more drugs
Panazole: resistant against all azoles tested
Denning, Verweij, 2009

20. Cross resistance
Cross-resistance between azole drugs appears to exist in vivo and in vitro and depends on specific mutations in Cyp51A
Between ITC and POS
Not so evident between ITC and VOR
Oakley 2000, Moore 2000

21. Conclusion Increase in some centres In vivo and in vitro
Associated with prolonged azole treatment
Molecular mechanisms are well knwon