Transcript PowerPoint-Präsentation

Is azole resistance increasing amongst
Aspergillus species?
Lass-Flörl Cornelia
Innsbruck Medical University
Divison of Hygiene and Medical Microbiology
Innsbruck Medical University
Faculty disclosure
• Invited speaker: Pfizer, Gilead, MSD, ScheringPlough
• Consultant: Pfizer, Gilead, Schering-Plough
• Research Grants: Pfizer, Gilead, Schering-Plough
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,…)
Increasing Concentrations
AmB
5FC
FLU
ITRA
VORI
CASPO
candida
MICs defined via E-test
Growth of fungus
MIC= zone of inhibition
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
Facing In Vitro/In Vivo Correlation
with Fungi
Aspergillus terreus
Amphotericin B Intrinsic
Candida glabrata
Azoles
Candida krusei
Candida lusitaniae
Intrinsic and
acquired
Intrinsic
Azoles
Amphotericin B Intrinsic and
acquired
Histoplasma capsulatum Fluconazole
Acquired
Has Antifungal Susceptibility Testing Come of Age?
Pfaller, Rex 2002
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)
• 1945-1998: 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
In vivo resistance
• 2002 first cases of what appears to be multipleazole 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
Multiple-triazole-resistant
aspergillosis.
Verweij PE, Mellado E, Melchers WJ
N Engl J Med. 2007 356 (14):1481-3.
Clinical Feature
Primary resistance
Secondary
resistance
In vivo-in vitro
correlation
Risk factors
Cross-resistance
Multi-drug azole
resistance
Outcome
+
++
++
Long term azole
treatment: ++
Long term azole
prophylaxis: ++
++
++
Lethal: ++
Plus signs (+) indicate the severity
Lass-Flörl, 2009
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.
Azoles: Voriconazole, Posaconazole, Itraconazole
Ergosterol
14-α-sterol demethylase
Lanosterol
Azole Resistance Mechanisms
Altered drug uptake
Increased drug efflux
1. Changes in drug import/export
cyp 51A
cyp 51A
Mutations in
cyp51A
2. Alterations in sterol biosynthesis
cyp 51A
cyp 51A
Overexpression of
drug target
AZOLE RESISTANT ASPERGILLUS FUMIGATUS
Amino acid changes
M220I, M220V, M220K,
M220T
G54R, G54E, G54W,
G54V
L98H
G138C
Resistant drugs
ITC-resistance and reduced
activity to POS, VOR, RAV
ITC and POS
Multidrug-azole resistance
(ITC, POS, VOR,
ravuconazole)
ITC, VRC and long-term
treatment
Mellado (2004,2005, 2007), Verweij 2007, Snelders 2009
Defintions: Azole- Resistance
1. Azole:a single drug resistance (ITC and
VOR > 4µg/ml, POS > 2µg/ml)
2. Multi-azole resistance: resistant against at
least two or more drugs
3. Panazole: resistant against all azoles tested
Denning, Verweij, 2009
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
Conclusion
•
•
•
•
Increase in some centres
In vivo and in vitro
Associated with prolonged azole treatment
Molecular mechanisms are well knwon