Evaluation of the influence of different antifungal clinical
breapkpoints to susceptibility testing of candidemia isolates
from 7 Belgian hospitals
C. Van Laer1*,2, K. Lagrou2, P. Vandecandelaere3*, AM. Van den Abeele4*, J. Frans5*, R. Cartuyvels6*, E. Oris7*, H. De Beenhouwer1*, K. Van
Vaerenbergh1*, A. Boel1*
1
OLV Hospital, Aalst, 2 University Hospitals Leuven, Leuven, 3 Jan Yperman Hospital, Ieper, 4 Sint-Lucas Hospital, Ghent, 5 Imelda Hospital, Bonheiden,
Hospital, Hasselt, 7 Hospital Zuid-Oost Limburg, Genk; Belgium. *On behalf of the BILULU study group.
6
Jessa
contact: christine.1.vanlaer@uzleuven.be
Introduction
Materials and methods
EUCAST V3.0, CLSI M27-S3
and revised CLSI 2011 define
different clinical breakpoints
(CBPs) for antifungals.
This study evaluates the
influence of using these
three different CBPs on the
susceptibility reporting of
Candida isolates from blood
cultures from 7 Belgian
hospitals.
From December 2010 till August 2011, 104 Candida spp. isolated from blood cultures (no
duplicates) were collected in 7 Belgian hospitals: Onze Lieve Vrouw Hospital, Aalst (n=10);
University Hospitals Leuven, Leuven (n=55); Jan Yperman Hospital, Ieper (n=8); Sint-Lucas
Hospital, Ghent (n=5); Imelda Hospital, Bonheiden (n=6); Jessa Hospital, Hasselt (n=10);
Hospital Zuid-Oost Limburg, Genk (n=10).
All isolates were identified to species level by ITS2 fragment length analysis. Susceptibility
testing was performed in one centre on RPMI agar (AES Chemunex Laboratoire, Bruz Cedex,
France) with E-test (Etest® BioMérieux, Marcy-l’Etoile, France) for fluconazole, voriconazole,
anidulafungin, caspofungin and amphotericin B. As QC ATCC 22019 C. parapsilosis and ATCC
6258 C. krusei were used. Susceptibility results were interpreted according to 3 different
breakpoint guidelines (EUCAST V3.0, CLSI M27-S3 and revised CLSI 2011) for a total of 99
strains from spp. with more than 2 isolates: C. albicans (n=56), C. glabrata (n=35) and C.
parapsilosis (n=8).
Results
All C. albicans isolates were susceptible for fluconazole, voriconazole, caspofungin and anidulafungin when using the 3 different
guidelines, except one strain with a MIC of 0,38 µg/mL for caspofungin (CLSI: S, revised CLSI: S-DD).
For C. glabrata EUCAST discourages use of fluconazole and voriconazole, indicating that there is insufficient evidence. For
fluconazole, 21 strains interpreted as S when using CLSI, became S-DD when using revised CLSI. Two isolates were R with both
CLSI CBPs. The same strains were also voriconazole R according CLSI M27-S3, while all other strains were S. In the absence of
CBPs for voriconazole, revised CLSI recommends to use the epidemiologic cutoff value (ECV), 0,50 µg/mL (3). Three strains had a
MIC >0,5 µg/mL (non wild-type strains). Revised CLSI lowered CBPs for echinocandins: using CLSI all C. glabrata strains were S
for caspofungin, but with revised CLSI 16 isolates were S-DD. For anidulafungin all isolates were S according the 3 CBPs. The MICs
should be interpreted with caution, because E-test was used instead of the reference method. Lower MICs for anidulafungin
than for caspofungin when using E-test has been described by M. Arendrup (2).
Despite higher CBPs for anidulafungin in comparison with other species, half of the C. parapsilosis strains (4/8) were R using
CLSI, and S-DD using revised CLSI. In contrast all strains were S for caspofungin.
For amphotericin B, only EUCAST CBPs are available. One C. albicans, 1 C. glabrata and 4 C. parapsilosis were S-DD. The other
isolates were S for amphotericin B.
C. albicans (n=56)
C. glabrata (n=35)
C. parapsilosis (n=8)
Breakpoints
Interpretion
Breakpoints
Interpretion
Breakpoints
Interpretion
Antifungal
CBP
S-DD/I
S-DD/I
S-DD/I
S
R
S S-DD/I R
S
R
S S-DD/I R
S
R
S S-DD/I R
EUCAST
<2
2-4
>4
56
0
0
IE
IE
IE
<2
2-4
>4
8
0
0
Fluconazole
CLSI M27-S3
≤8
16-32
≥64
56
0
0
≤8
16-32
≥64
21
12
2
≤8
16-32
≥64
8
0
0
CLSI revised
≤2
4
≥8
56
0
0
≤32
≥64
33
2
≤2
4
≥8
8
0
0
EUCAST
<0,125 0,125 >0,125 56
0
0
IE
IE
IE
<0,125 0,125 >0,125
8
0
0
Voriconazole CLSI M27-S3
≤1
2
≥4
56
0
0
≤1
2
≥4
33
0
2
≤1
2
≥4
8
0
0
CLSI revised
ECV = 0,5 (3)
≤0,12
0,50
≥1
56
0
0
≤0,12 0,25-0,50
≥1
8
0
0
EUCAST
Caspofungin
CLSI M27-S3
≤2
>2
56
0
≤2
>2
35
0
0
≤2
>2
8
0
CLSI revised
≤0,25
0,50
≥1
55
1
0
≤0,12
0,25
≥0,5
19
16
0
≤2
4
≥8
8
0
0
EUCAST
<0,03
0,03
>0,03
56
0
0
<0,06
0,06
>0,06
35
0
0
Anidulafungin CLSI M27-S3
≤2
>2
56
0
0
≤2
>2
35
0
≤2
>2
4
4
CLSI revised
≤0,25
0,50
≥1
56
0
0
≤0,12
0,25
≥0,5
35
0
0
≤2
4
≥8
4
4
0
EUCAST
<1
1
>1
55
1
<1
1
>1
34
1
0
<1
1
>1
4
4
0
Amphotericin B CLSI M27-S3
CLSI revised
Table 1: Clinical breakpoints (in µg/mL) of EUCAST, CLSI M27-S3 and CLSI revised for C. albicans, C. glabrata, C. parapsilosis and interpretation of tested strains according the
different CBPs (ECV: epidemiologic cutoff value, IE: insufficient evidence, -: no CBP)
Conclusions
The changes in CBPs in the newer
guidelines affect especially
C. glabrata.
References
(1) CLSI Reference Method for Broth Dilution Antifungal Susceptibility Testing of Yeasts; 3th Informational
Supplement, M27-S3, vol 28 n°15
(2) M. Arendrup, Susceptibility testing of Fungi, Antwerp 2011, Fungal infections and frustrations across the border
(3) Pfaller et al, Triazole and Echinocandin MIC Distributions with Epidemiological Cutoff Values for Differentiation of
Wild-Type Strains from Non-Wild-Type Strains of Six Uncommon Species of Candida, J Clin Microbiol 2011; 49(2):
630–637
Acknowledgement: The authors thank Pfizer for the supply of materials for susceptibility testing: E-test and RPMI
agars