Previous Article | Next Article 
Journal of Clinical Microbiology, November 2001, p. 4181-4183, Vol. 39, No. 11
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.11.4181-4183.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Trends in Antifungal Susceptibility among Swedish
Candida Species Bloodstream Isolates from 1994 to 1998:
Comparison of the E-test and the Sensititre YeastOne Colorimetric
Antifungal Panel with the NCCLS M27-A Reference Method
Erja
Chryssanthou*
Department of Clinical Microbiology,
Karolinska Hospital, Stockholm, Sweden
Received 16 April 2001/Returned for modification 30 July
2001/Accepted 30 August 2001
 |
ABSTRACT |
A comparative evaluation of the NCCLS macrodilution method, the
E-test, and the Sensititre YeastOne Colorimetric Antifungal Panel for
the susceptibility testing of fluconazole, itraconazole, amphotericin
B, and flucytosine was conducted with 233 blood isolates of
Candida species collected between 1994 and 1998 in
Sweden. Antifungal susceptibility profiles of Candida
albicans and non-C. albicans
Candida species remained essentially unchanged within the
5-year study period. The overall agreement rates for the E-test and the
NCCLS MICs and for the YeastOne and the NCCLS MICs were 
86 and
87%, respectively, within ±1 dilution for fluconazole, amphotericin
B, and flucytosine, and 66 and 57%, respectively, for
itraconazole. The E-test and the YeastOne panels are equivalent, and
both are convenient methods for routine use.
| |
TEXT |
Non-Candida
albicans Candida species are frequently isolated from
bloodstream infections, although C. albicans remains the most common species (12). Susceptibility to antifungal
drugs varies among different species of Candida, which
highlights the importance of species identification and antifungal MIC
determination (7, 11, 14). With the advent of the NCCLS
reference method for antifungal susceptibility testing, it is now
possible to compare and evaluate alternative, easier-to-perform methods
(6). The commercially available E-test and Sensititre
YeastOne antifungal panel have both demonstrated good agreement with
the NCCLS method in previous studies (2, 3, 4, 16).
Here we present the first nationwide retrospective epidemiological
survey of antifungal susceptibility patterns of Candida species isolated from blood cultures, initiated in 1998 by the Swedish
Reference Group for Antimycotics
Methodology. Moreover, we compared
the NCCLS procedure with the E-test and the YeastOne antifungal panel
in order to evaluate these commercial methods for routine testing of
antifungal agents.
Clinical isolates.
Candida species blood isolates
collected between 1994 and 1998 were requested from 15 Swedish
microbiological laboratories. A total of 499 Candida species
isolates (C. albicans, n = 371; non-C. albicans Candida spp., n = 128) were received, and 233 isolates were selected for the study. They
comprised C. albicans (n = 123), C. glabrata (n = 52), C. parapsilosis
(n = 33), C. tropicalis (n = 11), C. krusei (n = 9), and C. lusitaniae (n = 5). Isolates were identified
by standard methods and stored frozen at 
70°C until use. Prior to
antifungal testing, each isolate was subcultured twice on Sabouraud's
dextrose agar (Oxoid). C. krusei ATCC 6258 and C. parapsilosis ATCC 22019 were used as controls.
Susceptibility testing.
Broth macrodilution testing was
performed in accordance with the NCCLS M27-A guidelines
(6). Antifungal agents were obtained from their respective
manufacturers. The final drug concentration ranges were 0.125 to 64 µg/liter for fluconazole, 0.0313 to 64 µg/liter for flucytosine,
0.0313 to 16 µg/liter for itraconazole, and 0.125 to 4 mg/liter for
amphotericin B. The E-tests (AB Biodisk, Stockholm, Sweden) were
performed in accordance with the manufacturer's instructions. The MIC
endpoints were determined after 48 h of incubation at 35°C.
Sensititre YeastOne test panels (kindly supplied by AccuMed
International Ltd., East Grinstead, United Kingdom) were processed in
accordance with the manufacturer's instructions. The plates were
incubated at 35°C, and the MICs were read after 24 h if the
growth control well was red; otherwise, they were read after 48 h.
Data analysis.
Both on-scale and off-scale MICs were included
in the analysis. The low off-scale MICs were left unchanged, and the
high off-scale MICs were converted to the next highest concentration.
I studied the antifungal susceptibility patterns of 233 Candida sp. blood isolates cultured between 1994 and 1998 in
Sweden. With the NCCLS method, yearly MICs for 50% of the C. albicans and non-C. albicans Candida species
studied (MIC50s) remained constant within the
5-year study period (data not shown). Equivalent MIC50s and MIC90s were
obtained by all three methods for C. albicans isolates.
Compared to those obtained by the NCCLS method, the flucytosine
MIC90s and itraconazole
MIC50s obtained by the E-test were higher for
non-C. albicans isolates. On the other hand, the YeastOne method produced lower fluconazole, itraconazole, and flucytosine MIC50s and
MIC90s for non-C. albicans
isolates (Table 1).
View this table:
[in this window]
[in a new window]
|
TABLE 1.
In vitro susceptibilities of Candida blood
isolates cultured between 1994 and 1998 to fluconazole, itraconazole,
flucytosine, and amphotericin B by the NCCLS macrodilution, E-test, and
Sensititre YeastOne methodsa
|
|
The overall agreement between the MICs obtained by the E-test and NCCLS
macrodilution methods was
86% within ±1 dilution
for fluconazole,
amphotericin B, and flucytosine and
66% for
itraconazole (Table
2). The overall agreement between the
MICs
obtained by the YeastOne and NCCLS methods was
87% for
fluconazole,
amphotericin B, and flucytosine and
57% for
itraconazole. The
discrepancies between the YeastOne panel and the
NCCLS macrodilution
method results consisted mainly of lower
itraconazole MICs, which
were observed for 187 isolates. E-tests, on
the other hand, gave
higher itraconazole MICs for 119 isolates.
The categorization of
Candida species within the established
breakpoints of resistance for fluconazole (MIC,
64 mg/liter),
itraconazole (MIC
1 mg/liter), and flucytosine (MIC
32 mg/liter),
obtained by the three methods, is given in Table
3. Resistance
to fluconazole,
itraconazole, and flucytosine was almost entirely
accounted for by
C. glabrata,
C. krusei, and, to a minor extent,
C. parapsilosis isolates. Of 233 isolates, 15% were
resistant
to fluconazole by the NCCLS method, 12 were resistant by the
E-test
method, and 9% were resistant by the YeastOne method.
Itraconazole
resistance was found in 23% of the isolates by the NCCLS
method,
in 28% by the E-test method, and in 13% by the YeastOne
method.
View this table:
[in this window]
[in a new window]
|
TABLE 3.
Categorization of Candida species within the
established breakpoints for resistance to fluconazole, itraconazole,
and flucytosine
|
|
I found essentially unchanged antifungal susceptibility profiles of 233 Swedish
C. albicans and non-
C. albicans
Candida sp.
bloodstream isolates within the 5-year study period.
Constant
fluconazole susceptibility among
Candida isolates
other than
C. glabrata and
C. krusei was recently
also reported in the United
States (
9). Conversely, Baran
et al. found a trend toward slightly
increasing fluconazole MICs
(
1). Our MIC
50s for
C. albicans agree with those reported in North and South America
(
7,
10).
Aside from
C. glabrata,
C. krusei, and, to a minor extent,
C. parapsilosis, there
were almost no fluconazole-, itraconazole-,
and flucytosine-resistant
isolates in Sweden. This has also been
reported in other countries in
Europe (
8) and in North and
Latin America (
9,
10). Azole resistance among Swedish
C. glabrata
isolates was considerably more frequent than the 6.7%
fluconazole and
32.8% itraconazole resistance recently reported
in the United States
(
10), while no fluconazole resistance was
found among
Latin American and Canadian isolates (
14).
The performance of both the E-test and the YeastOne panel was
comparable to that of the NCCLS reference for
C. albicans
(
2,
3,
5). In general, the E-test tended to give higher
MIC
50s
of flucytosine and itraconazole among
non-
C. albicans Candida isolates. Similar
findings have previously been reported for
C. krusei
and
C. tropicalis isolates, respectively (
2,
5).
The YeastOne method gave lower fluconazole,
itraconazole, and
flucytosine MICs, also observed for
C. glabrata,
C. tropicalis (
3), and
C. albicans (itraconazole) (
4), than the NCCLS
method.
To et al. previously reported lower amphotericin B, fluconazole,
and flucytosine MICs, when comparing the susceptibilities of some
Candida species by the Alamar blue method with those
obtained
with the NCCLS macrodilution method (
15), thereby
supporting
the findings reported here. The reasons for these
species-specific
discrepancies between the methods tested are not
known.
Overall, the agreement between the E-test and NCCLS methods and between
the YeastOne panel and the NCCLS method was good (
2,
3,
4,
13). However, we found lower agreement for itraconazole,
which
was in accord with a recent report (
5).
No amphotericin B-resistant isolates were identified, although the
E-test is claimed to be superior for the detection of less-susceptible
isolates (
17). The major discrepancy between the non-NCCLS
methods
concerned the itraconazole resistance of
C. glabrata,
C. krusei,
and
C. parapsilosis
isolates, which appeared to be resistant by
the E-test method but
susceptible by the YeastOne method. Both
the E-test and YeastOne
methods misclassified some
C. glabrata isolates that were
fluconazole resistant by the NCCLS method as
susceptible. This
is in contrast to one multicenter study of the
E-test method, in which
azole-susceptible isolates appeared to
be resistant (
18).
This is the first comparison of the NCCLS broth macrodilution, E-test,
and YeastOne methods for susceptibility testing of
Candida
species. The E-test is equivalent to the YeastOne panels,
and both are
simple and convenient methods for routine use. However,
because of
inconsistency, the results of azole susceptibility
testing of
C. glabrata,
C. krusei, and
C. parapsilosis
isolates
should be confirmed by a reference
method.
| |
FOOTNOTES |
*
Mailing address: Department of Clinical Microbiology,
L202 Karolinska Hospital, S-171 76 Stockholm, Sweden. Phone: (46)
851773566. Fax: (46) 8308099. E-mail:
Erja.Chryssanthou{at}ks.se.
| |
REFERENCES |
| 1.
|
Baran, J., Jr.,
E. Klauber,
J. Barczak,
K. Riederer, and R. Khatib.
2000.
Trends in antifungal susceptibility among Candida sp. urinary isolates from 1994 and 1998.
J. Clin. Microbiol.
38:870-871[Abstract/Free Full Text].
|
| 2.
|
Chen, S. C.,
M. L. O'Donnell,
S. Gordon, and G. L. Gilbert.
1996.
Antifungal susceptibility testing using the E test: comparison with the broth macrodilution technique.
J. Antimicrob. Chemother.
37:265-273[Abstract/Free Full Text].
|
| 3.
|
Davey, K. G.,
A. Szekely,
E. M. Johnson, and D. W. Warnock.
1998.
Comparison of a new commercial colorimetric microdilution method with a standard method for in-vitro susceptibility testing of Candida spp. and Cryptococcus neoformans.
J. Antimicrob. Chemother.
42:439-444[Abstract/Free Full Text].
|
| 4.
|
Espinel-Ingroff, A.,
M. Pfaller,
S. A. Messer,
C. C. Knapp,
S. Killian,
H. A. Norris, and M. A. Ghannoum.
1999.
Multicenter comparison of the Sensititre YeastOne colorimetric antifungal panel with the National Committee for Clinical Laboratory Standards M27-A reference method for testing clinical isolates of common and emerging Candida spp., Cryptococcus spp., and other yeasts and yeast-like organisms.
J. Clin. Microbiol.
37:591-595[Abstract/Free Full Text].
|
| 5.
|
Martín-Mazuelos, E.,
M. J. Gutiérrez,
A. I. Aller,
S. Bernal,
M. A. Martínez,
O. Montero, and G. Quindós.
1999.
A comparative evaluation of Etest and broth microdilution methods for fluconazole and itraconazole susceptibility testing of Candida spp.
J. Antimicrob. Chemother.
43:477-481[Abstract/Free Full Text].
|
| 6.
|
National Committee for Clinical Laboratory Standards.
1997.
Reference method for broth dilution antifungal susceptibility testing of yeasts. Approved standard M27-A, vol. 17, no. 9.
National Committee for Clinical Laboratory Standards, Wayne, Pa.
|
| 7.
|
Pfaller, M. A.,
R. N. Jones,
G. V. Doern,
H. S. Sader,
R. J. Hollis, and S. A. Messer, The SENTRY Participant Group..
1998.
International surveillance of bloodstream infections due to Candida species: frequency of occurrence and antifungal susceptibilities of isolates collected in 1997 in the United States, Canada, and South America for the SENTRY program.
J. Clin. Microbiol.
36:1886-1889[Abstract/Free Full Text].
|
| 8.
|
Pfaller, M. A.,
R. N. Jones,
G. V. Doern,
A. C. Fluit,
J. Verhoef,
H. Sader,
S. A. Messer,
A. Houston,
S. Coffman, and R. J. Hollis for The SENTRY Participant Group (Europe).
1999.
International surveillance of blood stream infections due to Candida species in the European SENTRY program: species distribution and antifungal susceptibility including the investigational triazole and echinocandin agents.
Diagn. Microbiol. Infect. Dis.
35:19-25[CrossRef][Medline].
|
| 9.
|
Pfaller, M. A.,
S. A. Messer,
R. J. Hollis,
R. N. Jones,
G. V. Doern,
M. E. Brandt, and R. A. Hajjeh.
1999.
Trends in species distribution and susceptibility to fluconazole among blood stream isolates of Candida species in the United States.
Diagn. Microbiol. Infect. Dis.
33:217-222[CrossRef][Medline].
|
| 10.
|
Pfaller, M. A.,
R. N. Jones,
G. V. Doern,
H. S. Sader,
S. A. Messer,
A. S. Houston,
R. Coffman,
J. Hollis, and The SENTRY Participant Group.
2000.
Bloodstream infections due to Candida species: SENTRY antimicrobial surveillance program in North America and Latin America, 1997-1998.
Antimicrob. Agents Chemother.
44:747-751[Abstract/Free Full Text].
|
| 11.
|
Sandven, P.,
L. Bevanger,
A. Digranes,
P. Gaustad,
H. Haukland,
M. Steinbakk, and The Norwegian Yeast Study Group.
1998.
Constant low rate of fungemia in Norway, 1991 to 1996.
J. Clin. Microbiol.
36:3455-3459[Abstract/Free Full Text].
|
| 12.
|
Sandven, P.
2000.
Epidemiology of candidemia.
Rev. Iberoam. Micol.
17:73-81[Medline].
|
| 13.
|
Sewell, D. L.,
M. A. Pfaller, and A. L. Barry.
1994.
Comparison of broth macrodilution, broth microdilution, and E test antifungal susceptibility tests for fluconazole.
J. Clin. Microbiol.
32:2099-2102[Abstract/Free Full Text].
|
| 14.
|
St-Germain, G.,
M. Lavardière,
R. Pelletier,
A.-M. Bourgault,
M. Libman,
C. Lemieux, and G Noel.
2001.
Prevalence and antifungal susceptibility of 442 Candida isolates from blood and other normally sterile sites: results of a 2-year (1996 to 1998) multicenter surveillance study in Quebec, Canada.
J. Clin. Microbiol.
39:949-953[Abstract/Free Full Text].
|
| 15.
|
To, W.-K. A. W.,
Fothergill, and M. G. Rinaldi.
1995.
Comparative evaluation of macrodilution and Alamar colorimetric microdilution broth methods for antifungal susceptibility testing of yeast isolates.
J. Clin. Microbiol.
33:2660-2664[Abstract].
|
| 16.
|
van Eldere, J.,
L. Joosten,
A. Verhaeghe, and I. Surmont.
1996.
Fluconazole and amphotericin B antifungal susceptibility testing by National Committee for Clinical Laboratory Standards broth macrodilution method compared with E-test and semiautomated broth microdilution test.
J. Clin. Microbiol.
34:842-847[Abstract].
|
| 17.
|
Wanger, A.,
K. Mills,
P. W. Nelson, and J. H. Rex.
1995.
Comparison of E test and National Committee for Clinical Laboratory Standards broth macrodilution method for antifungal susceptibility testing: enhanced ability to detect amphotericin B-resistant Candida isolates.
Antimicrob. Agents Chemother.
39:2520-2522[Abstract].
|
| 18.
|
Warnock, D. W.,
E. M. Johnson, and T. R. Rogers on behalf of The BSAC Working Party on Antifungal Chemotherapy..
1998.
Multi-centre evaluation of the E test method for antifungal drug susceptibility testing of Candida spp. and Cryptococcus neoformans.
J. Antimicrob. Chemother.
42:321-331[Abstract/Free Full Text].
|
Journal of Clinical Microbiology, November 2001, p. 4181-4183, Vol. 39, No. 11
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.11.4181-4183.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
This article has been cited by other articles:
-
Pfaller, M. A., Diekema, D. J.
(2007). Epidemiology of Invasive Candidiasis: a Persistent Public Health Problem. Clin. Microbiol. Rev.
20: 133-163
[Abstract]
[Full Text]
-
Girmenia, C., Pizzarelli, G., Cristini, F., Barchiesi, F., Spreghini, E., Scalise, G., Martino, P.
(2006). Candida guilliermondii Fungemia in Patients with Hematologic Malignancies.. J. Clin. Microbiol.
44: 2458-2464
[Abstract]
[Full Text]
-
Pfaller, M. A., Diekema, D. J., Sheehan, D. J.
(2006). Interpretive Breakpoints for Fluconazole and Candida Revisited: a Blueprint for the Future of Antifungal Susceptibility Testing. Clin. Microbiol. Rev.
19: 435-447
[Abstract]
[Full Text]
-
Takakura, S., Fujihara, N., Saito, T., Kudo, T., Iinuma, Y., Ichiyama, S., the Japan Invasive Mycosis Surveillance Study Grou,
(2004). National surveillance of species distribution in blood isolates of Candida species in Japan and their susceptibility to six antifungal agents including voriconazole and micafungin. J Antimicrob Chemother
53: 283-289
[Abstract]
[Full Text]
-
Pfaller, M. A., Diekema, D. J., Messer, S. A., Boyken, L., Hollis, R. J.
(2003). Activities of Fluconazole and Voriconazole against 1,586 Recent Clinical Isolates of Candida Species Determined by Broth Microdilution, Disk Diffusion, and Etest Methods: Report from The ARTEMIS Global Antifungal Susceptibility Program, 2001. J. Clin. Microbiol.
41: 1440-1446
[Abstract]
[Full Text]
-
Pfaller, M. A., Diekema, D. J.
(2002). Role of Sentinel Surveillance of Candidemia: Trends in Species Distribution and Antifungal Susceptibility. J. Clin. Microbiol.
40: 3551-3557
[Full Text]
-
Chryssanthou, E., Cuenca-Estrella, M.
(2002). Comparison of the Antifungal Susceptibility Testing Subcommittee of the European Committee on Antibiotic Susceptibility Testing Proposed Standard and the E-Test with the NCCLS Broth Microdilution Method for Voriconazole and Caspofungin Susceptibility Testing of Yeast Species. J. Clin. Microbiol.
40: 3841-3844
[Abstract]
[Full Text]
Top
Abstract
Text
