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In vitro activity of four triazole antifungal drugs against clinically common and uncommon yeast species

Abstract

Background and purpose: Incidence of fungal infections caused by opportunistic fungal pathogens, such as yeasts and yeast-like species, has undergone an increase in otherwise healthy individuals. These pathogens account for high mortality and show reduced susceptibility to the routine antifungal drugs. Accordingly, antifungal susceptibility testing is an urgent need in the determination of the susceptibility spectrum of antifungals and selection of appropriate antifungal agents for the management of patients with fungal infection. Materials and methods: The present study was conducted on 110 yeast strains belonging to 15 species recovered from clinical specimens. Susceptibility of the isolates to four antifungal drugs (i.e., fluconazole, itraconazole, voriconazole, and posaconazole) was tested according to the Clinical and Laboratory Standards Institute guidelines M27-A3 and M27-S4. Results: Fluconazole exhibited no activity against 4.3% (n=2) of C. albicans isolates, whereas the remaining 44 isolates had a minimum inhibitory concentration (MIC) range of 0.125-4 μg/ml. Voriconazole had the lowest geometric mean MIC (0.03 µg/ml) against all isolated yeast species, followed by posaconazole (0.07 µg/ml), itraconazole (0.10 µg/ml), and fluconazole (0.60 µg/ml). Overall, all of the isolates had reduced voriconazole MICs with a MIC range of 0.016-0.5 μg/ml, except for one isolate of C. albicans that had a MIC of 1 μg/ml. Candida haemulonii as a multidrug-resistant fungus showed a fluconazole MIC of > 64 μg/ml. Conclusion: The current study provides insight into the antifungal susceptibility profiles of clinically common and uncommon yeast species to four triazole antifungal agents. According to our findings, voriconazole was the most active agent. Awareness about antifungal susceptibility patterns is highly helpful in the selection of appropriate antifungal drugs and identification of the efficiency of the currently used agents.
Current Medical Mycology
2019, 5(4): 14-19
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In vitro activity of four triazole antifungal drugs against
clinically common and uncommon yeast species
Narges Aslani1, Tahereh Shokohi2, Mohammad Reza Ataollahi3, Saham Ansari4, Yousef Gholampour5, Ali
Khani Jeihooni6, Mohammad Hosein Afsarian7*
1
Infectious and Tropical Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
2
Department of Medical Mycology, School of Medicine, Mazandaran University of Medical Sciences, Sari, Iran
3
Department of Medical Immunology, School of Medicine, Fasa University of Medical Sciences, Fasa, Iran
4
Department of Parasitology and Mycology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
5
Department of Internal Medicine, School of Medicine, Fasa University of Medical Sciences, Fasa, Iran
6
Department of Public Health, School of Health, Fasa University of Medical Sciences, Fasa, Iran
7
Department of Medical Mycology and Parasitology, School of Medicine, Fasa University of Medical Sciences, Fasa, Iran
Article Info
A B S T R A C T
Article type:
Original article
Background and Purpose: Incidence of fungal infections caused by opportunistic
fungal pathogens, such as yeasts and yeast-like species, has undergone an increase in
otherwise healthy individuals. These pathogens account for high mortality and show
reduced susceptibility to the routine antifungal drugs. Accordingly, antifungal
susceptibility testing is an urgent need in the determination of the susceptibility spectrum
of antifungals and selection of appropriate antifungal agents for the management of
patients with fungal infection.
Materials and Methods: The present study was conducted on 110 yeast strains
belonging to 15 species recovered from clinical specimens. Susceptibility of the isolates
to four antifungal drugs (i.e., fluconazole, itraconazole, voriconazole, and posaconazole)
was tested according to the Clinical and Laboratory Standards Institute guidelines M27-
A3 and M27-S4.
Results: Fluconazole exhibited no activity against 4.3% (n=2) of C. albicans isolates,
whereas the remaining 44 isolates had a minimum inhibitory concentration (MIC) range
of 0.125-4 μg/ml. Voriconazole had the lowest geometric mean MIC (0.03 µg/ml)
against all isolated yeast species, followed by posaconazole (0.07 µg/ml), itraconazole
(0.10 µg/ml), and fluconazole (0.60 µg/ml). Overall, all of the isolates had reduced
voriconazole MICs with a MIC range of 0.016-0.5 μg/ml, except for one isolate of C.
albicans that had a MIC of 1 μg/ml. Candida haemulonii as a multidrug-resistant fungus
showed a fluconazole MIC of > 64 μg/ml.
Conclusion: The current study provides insight into the antifungal susceptibility profiles
of clinically common and uncommon yeast species to four triazole antifungal agents.
According to our findings, voriconazole was the most active agent. Awareness about
antifungal susceptibility patterns is highly helpful in the selection of appropriate
antifungal drugs and identification of the efficiency of the currently used agents.
Keywords: Antifungal agents, In vitro susceptibility, Yeast species
Article History:
Received: 31 May 2019
Revised: 25 October 2019
Accepted: 03 December 2019
* Corresponding author
:
Mohammad Hosein Afsarian
Department of Medical Mycology
and Parasitology, School of Medicine,
Fasa University of Medical Sciences,
Fasa, Iran.
Email: afsariyan@gmail.com
How to cite this paper
Aslani N, Shokohi T, Ataollahi MR, Ansari S, Gholampour Y, Khani Jeihooni A, Afsarian MH. In vitro activity of four triazole
antifungal drugs against clinically common and uncommon yeast species. Curr Med Mycol. 2019; 5(4): 14-19. DOI:
10.18502/cmm.5.4.1949
Introduction
ver the last few years, the incidence of fungal
infections caused by opportunistic fungal
pathogens, such as yeasts and yeast-like
species, has witnessed a dramatic increase. The
most important yeasts isolated from clinical specimens
are Candida species. These species infect hospitalized
patients, especially those admitted to intensive care
units or oncology wards. According to the statistics,
invasive Candida infection is associated with mortality
having a range of 40-70% [1-3].
While Candida albicans continues to be a major
cause of candidiasis, however, the evidence is
indicative of the emergence of other Candida and
uncommon yeast species with high mortality and
reduced susceptibility to the currently administered
antifungal drugs. Some of these species isolated from
different clinical sources include C. parapsilosis,
Kluyveromyces marxianus (C. kefyr), Meyerozyma
guilliermondii (C. guilliermondii), C. intermedia, C.
lusitaniae, C. haemulonii, C. auris, and atypical forms
of Candida albicans (i.e., Candida africana, Candida
dubliniensis, and Candida stellatoidea) [4-7].
O
Aslani N et al. In vitro activity against yeast species
Curr Med Mycol, 2019, 5(4): 14-19 15
The routine antifungal agents for candidiasis
treatment are still restricted to polyenes, azoles, and the
recently developed echinocandins [8, 9]. Toxic effects
of amphotericin B as an efficient polyene antifungal
agent have limited the application of this medicine for
humans [8]. Minimal side effects and high therapeutic
index of azole compounds have made them as first-line
therapy for the treatment of Candida infections (for
many years), antifungal prophylaxis, and empirical or
pre-emptive treatment [10]. Nevertheless, the number
of Candida species with variable susceptibilities or
acquired resistance to these antifungal agents has been
on a growing trend over the past decade [11].
Determination of the antifungal susceptibility
patterns of yeast species isolated from clinical sources
and the selection of appropriate antifungal agents can
be useful for the management of fungal infection.
Regarding this, the current investigation was conducted
to evaluate the in vitro antifungal susceptibility of a
large number of yeast strains isolated from different
clinical sources to four triazole antifungal agents,
namely fluconazole, voriconazole, itraconazole, and
posaconazole, using microdilution broth method.
Materials and Methods
Isolates
This study was conducted on 110 yeast and yeast-
like species isolated from the nail (n=46), skin (n=36),
bronchoalveolar lavage (n=9), sputum (n=7), mouth
(n=5), mucosa (n=3), vagina (n=2), ear discharge
(n=1), and urine (n=1) during 8 months [12]. The
isolates were obtained from the Reference Culture
Collection of Invasive Fungi Research Center in Sari,
Iran. They had been previously identified through
polymerase chain reaction-restriction fragment length
polymorphism (PCR-RFLP), PCR amplification of
hwp1 gene, and sequencing [12].
Antifungal susceptibility testing
In vitro antifungal susceptibility tests were assayed
for Candida species using minimum inhibitory
concentrations (MICs). These isolates had been
identified as C. albicans (n=46), C. parapsilosis
(n=17), C. tropicalis (n=13), C. guilliermondii
(n=12), C. glabrata (n=4), P. kudriavzevii (C. krusei;
n = 4), C. famata (n=3), K. marxianus (C. kefyr; n=2),
C. haemulonii (n=2), C. intermedia (n=1), C.
sorbosivorans (n=1), C. stellatoidea (n=1), C. africana
(n=1), Trichosporon jirovecii (n=2), and T. asahii
(n=1). The in vitro antifungal susceptibility testing of
these species had been based on broth microdilution
method following the M27-A3 and M27-S4 guidelines
of the Clinical and Laboratory Standards Institute
(CLSI) [13, 14].
Fluconazole (Sigma-Aldrich, USA) was dissolved
in deionized-distilled water. Furthermore, itraconazole
(Sigma-Aldrich, USA), voriconazole (Sigma-Aldrich,
USA), and posaconazole (Sigma-Aldrich, USA) were
dissolved in dimethyl sulfoxide (Sigma). Fluconazole
was prepared at a final concentration of 0.063-64
μg/ml, while a concentration of 0.016-16 µg/ml was
considered for itraconazole, voriconazole, and
posaconazole. For the purpose of the study, RPMI 1640
medium containing L-glutamine without bicarbonate
(Gibco, UK) buffered to pH 7 with 0.165 mol/l 3-N-
morpholinepropanesulfonic acid (MOPS, Sigma) was
used. Drug-free and yeast-free controls were also
included in the study for comparative purposes.
Plates were stored at -70°C until they were used.
Briefly, all isolates were grown on potato dextrose agar
(PDA, Difco, Leeuwarden, the Netherlands) plates at
35°C for up to 3 days. Inoculum suspensions were
prepared in a sterile saline solution and then adjusted
spectrophotometrically at a wavelength of 530 nm and
a percent transmission range of 75-77%. The
microdilution plates were incubated at 35°C and read
visually after 24 h to determine the MIC values of the
antifungal agents. The P. kudriavzevii (C. krusei)
ATCC 6258 and C. parapsilosis ATCC 22019 were
used as quality control strains, and analysis of these
strains was performed with every new batch of MIC
plates. The MIC endpoints for all antifungals were
defined as the lowest drug concentration causing 50%
growth inhibition, compared with the growth of a drug-
free control.
Ethical Statement
The current study was approved by the Ethics
Committee of Fasa University of Medical Sciences
ethical code: 93210/D,97,247016), Fasa, Iran, and
written informed consent was obtained from the
patients.
Results
Antifungal susceptibility testing
Table 1 summarizes the results of the MIC range,
geometric mean MIC, MIC50, and MIC90 of four
triazole antifungal drugs against a total of 110
clinically Candida species and uncommon yeasts
obtained from 14 different Candida species and two
Trichosporon species. However, MIC90 was not
measured when fewer than nine isolates were available.
Candida albicans complex isolates (C. stellatoidea and
C. africana) showed high susceptibility to the tested
antifungal agents. As the results indicated, fluconazole
had the widest range and highest MICs against the
isolates (0.063-64 µg/ml).
The MIC ranges in all clinical strains against
antifungal drugs were as follows, in increasing order:
posaconazole and voriconazole (0.016-1 µg/ml),
itraconazole (0.016-4 µg/ml), and fluconazole (0.063-
64 µg/ml). Basically, voriconazole, posaconazole, and
itraconazole had low MIC50 against all tested clinical
strains (Table 1). Overall, in terms of GM MICs,
voriconazole was found to be the most active agent
against all isolates (n=110), followed by posaconazole
in comparison with itraconazole and fluconazole.
Furthermore, most of P. kudriavzevii (C. krusei)
isolates were resistant to fluconazole but not to
voriconazole, posaconazole, or itraconazole. In
In vitro activity against yeast species Aslani N et al.
16 Curr Med Mycol, 2019, 5(4): 14-19
Table 1. In vitro susceptibility testing of 110 clinical isolates of yeast species to four triazole antifungal agents (minimum inhibitory concentration range, geometric (G)
mean, MIC50, and MIC90 values are expressed in µg/ml)
MICs (μg/ml)
0.016
0.031
0.063
0.125
0.25
0.5
1
2 4
8
16
32
64
Range
MIC50/MIC90
Mode
G mean
drugs
All clinical strains (n = 110)
0.063-64
0.5/4
0.5
0.60
0.016-4
0.063/1
0.063
0.10
0.016-1
0.031/0.25
0.016
0.03
0.016-1
0.063/0.5
0.125
0.07
6
7
20
5
3
3
1
1
0.125-16
0.5/4
0.5
0.5
6
8
12
14
2
1
2
1
0.016-4
0.063/0.25
0.125
0.08
20
18
3
2
2
1
0.016-1
0.031/0.063
0.016
0.03
8
7
10
16
1
1
3
0.016-1
0.063/0.125
0.125
0.07
C. parapsilosis (n=17)
2
6
5
1
1
1
1
0.063-4
0.25/4
0.125
0.25
3
3
7
1
1
1
1
0.016-1
0.063/2
0.063
0.06
9
2
3
1
1
1
0.016-0.5
0.016/0.5
0.016
0.03
6
3
4
1
1
1
1
0.016-1
0.031/1
0.016
0.05
C. tropicalis (n=13)
2
2
4
2
1
1
1
0.063-4
0.25/2
0.25
0.32
2
3
4
2
1
1
0.016-0.5
0.063/0.25
0.063
0.06
7
4
1
1
0.016-0.125
0.016/0.063
0.016
0.02
6
2
1
2
1
1
0.016-0.5
0.031/0.25
0.016
0.04
C. guilliermondii (n=12)
2
2
3
3
1
1
0.063-2
0.25/1
-
0.28
2
2
3
3
1
1
0.016-0.5
0.063/0.25
-
0.07
5
2
3
1
1
0.016-0.25
0.031/0.125
0.016
0.03
3
3
2
2
1
1
0.016-0.5
0.031/0.25
-
0.05
1
1
1
1
4-32
-
-
-
1
1
1
1
0.25-4
-
-
-
1
1
1
1
0.016-0.5
-
-
-
1
1
1
1
0.063-1
-
-
-
Pichia kudriavzevii (= C. krusei, n=4)
1
3
32-64
-
-
-
1
1
2
1-4
-
-
-
2
2
0.25-0.5
-
-
-
1
1
2
0.25-1
-
-
-
2
1
0.5-1
-
-
-
1
2
0.063-0.125
-
-
-
2
1
0.031-0.063
-
-
-
1
1
1
0.031-0.125
-
-
-
Kluyveromyces marxianus (= C. kefyr, n=2)
1
1
0.5-1
-
-
-
1
1
0.125-0.25
-
-
-
1
1
0.031-0.125
-
-
-
1
1
0.063-0.25
-
-
-
C. haemulonii (n=2)
2
64
-
-
-
2
1
-
-
-
1
1
0.063-0.125
-
-
-
2
0.25
-
-
-
Trichosporon jirovecii (n=2)
1
1
0.5-1
-
-
-
2
0.125
-
-
-
1
1
0.031-0.063
-
-
-
1
1
0.063-0.125
-
-
-
C .intermedia (n=1)
1
0.5
-
-
-
1
0.125
-
-
-
1
0.016
-
-
-
1
0.031
-
-
-
C. sorbosivorans (n=1)
1
0.5
-
-
-
1
0.063
-
-
-
1
0.016
-
-
-
1
0.063
-
-
-
C. stellatoidea (n=1)
1
1
-
-
-
1
0.125
-
-
-
1
0.016
-
-
-
1
0.031
-
-
-
1
1
-
-
-
1
0.5
-
-
-
1
0.016
-
-
-
1
0.031
-
-
-
Trichosporon asahii (n=1)
1
1
-
-
-
1
0.125
-
-
-
1
0.031
-
-
-
1
0.063
-
-
-
VRZ, voriconazole; FLZ, Fluconazole; ITZ, Itraconazole; PSZ, posaconazole
contrast, C. guilliermondii, C. tropicalis, and C.
parapsilosis strains were highly susceptible to
fluconazole. Remarkably, C. guilliermondii was the
most susceptible strain to fluconazole, compared to C.
albicans and other non-albicans. In addition, C.
tropicalis was the most susceptible strain to
voriconazole. However, P. kudriavzevii (C. krusei) had
the highest voriconazole MIC value, compared to all
tested strains.
The MIC90 values of fluconazole were 4-log2-
Aslani N et al. In vitro activity against yeast species
Curr Med Mycol, 2019, 5(4): 14-19 17
dilution, 3-log2-dilution, and 2-log2-dilution less active
than those of voriconazole, posaconazole, and
itraconazole, respectively. The overall frequency of
fluconazole resistance in the evaluated data set was
4.3%. Most of the isolates were susceptible to
fluconazole. Notably, 6.5% (n=46), 5.9% (n=17), and
7.7% (n=13) of C. albicans, C. parapsilosis, and C.
tropicalis isolates were fluconazole-susceptible dose-
dependent (SDD), respectively. In this regard, each of
four species of C. glabrata was fluconazole-SDD with
a MIC value of ≤ 32.
All tested C. albicans isolates had low MICs for
posaconazole and itraconazole (MIC50=0.063 μg/ml).
In the current study, C. albicans, C. parapsilosis, C.
glabrata, and P. kudriavzevii (C. krusei) had the
resistance rates of 6.5% (3/46), 5.9% (1/17), 50% (2/4),
and 75% (3/4) to itraconazole, respectively. All isolates
of C. albicans showed reduced MICs for voriconazole
with a MIC range of 0.016-0.5 μg/ml, except for one
isolate that was resistant to voriconazole (MIC=1
μg/ml). However, 4.3% (n=46) of C. albicans and
11.8% (n=17) of the C. parapsilosis isolates were
voriconazole-SDD.
Notably, C. haemulonii as a multidrug-resistant
fungus showed a fluconazole MIC of > 64 μg/ml.
Moreover, C. albicans had elevated GM for
fluconazole (0.60 μg/ml) in comparison to that for
voriconazole (0.03 μg/ml). Overall, voriconazole had a
lower MIC90 value (0.25 mg/l) than posaconazole (0.5
mg/l), itraconazole (1 mg/l), and fluconazole (4 mg/l).
None of the T. jirovecii and T. asahii isolates were
found to be resistant to fluconazole, itraconazole,
posaconazole, or voriconazole.
Discussion
Frequency of fungal infections caused by
opportunistic fungal pathogens, particularly the genus
of Candida, has undergone a dramatic increase [15,
16]. Epidemiologically, most of the isolates withdrawn
from various clinical samples are C. albicans.
Nevertheless, the elevation of non-albicans Candida
and uncommon yeast species with reduced
susceptibility to routine antifungals is a serious
problem. This issue is much more complicated when
affecting patients with immunodeficiency due to the
likelihood of yeast invasion to the deeper tissues,
resulting in infection dissemination [17, 18].
Therefore, the determination of the antifungal
resistance patterns of clinical samples is a vital issue
facilitating the selection of appropriate antifungal
agents for the treatment of fungal infections and
surveillance of resistance to antifungal drugs. Azole
compounds are the most frequently used clinical
antifungal agents for the treatment of candidiasis.
However, with the overuse of these agents, the number
of drug-resistant fungal isolates is on a growing trend
[19]. Regarding this, the current study was focused on
the susceptibilities of various Candida species to
commonly used azole antifungal agents. The results of
the current research demonstrated that fluconazole had
desirable activities against most of the isolates.
Nevertheless, C. albicans isolates showed a
resistance rate of 4.3% against fluconazole in the
present study, which is in concordance with the
results reported in other studies (e.g., Almeida et al.
[5.5%] and Eksi et al. [5.7%]) [20, 21]. Furthermore,
Bhattacharjee reported that all of the C. albicans
strains isolated from blood cultures were susceptible
to fluconazole [22]. The results of a recent study
carried out by Aslani et al. showed that resistance to
fluconazole in the C. albicans strains isolated from
the oral cavity of cancer patients was higher (15.9%),
compared with the rate observed in the current study
(4.3%) [6]. In a study performed by Badiee et al.
[23], C. albicans, P. kudriavzevii (C. krusei), C.
glabrata, Kluyveromyces marxianus (C. kefyr), C.
parapsilosis, and C. tropicalis showed the
fluconazole resistance rates of 9.3% (16/172), 95.2%
(59/62), 95% (38/40), 5% (2/40), 27.7% (5/18), and
33.3% (2/6), respectively.
In a population-based study conducted by
Wisplinghoff et al. on 1,077 Candida species isolated
from bloodstream, 0.8% (3/478) of C. albicans,
100.0% (202/202) of C. glabrata, 2.9% (6/211) of C.
parapsilosis, and 4.9% (6/123) of C. tropicalis were
non-susceptible to fluconazole [24]. In addition,
Castanheira et al. reported the fluconazole resistance
rates of 11.9% and 11.6% for C. glabrata and C.
tropicalis, respectively. They also showed that
fluconazole inhibited 94.0% and 88.4% of C.
parapsilosis and C. tropicalis isolates, respectively
[25].
In line with the present results, Bhattacharjee
showed that 66.7% (n=6) of the C. haemulonii strains
were resistant to fluconazole [22]. In the current
study, 3 (6.5%) C. albicans, 1 (5.9%) C. parapsilosis,
and 1 (7.7%) C. tropicalis isolates were fluconazole-
SDD, respectively. Compared with our findings, Eksi
et al. detected dose-dependent susceptibility to
fluconazole in 11.3% and 5.2% of C. albicans and
non-albicans Candida, respectively [21]. It seems that
fluconazole remains an effective antifungal agent
against yeast species in spite of its widespread
application in Iran.
Most of the P. kudriavzevii (C. krusei) isolates were
detected to be resistant to fluconazole. The decreased
susceptibility to fluconazole in P. kudriavzevii (C.
krusei) isolates was noted in previous studies. Based on
the evidence, P. kudriavzevii (C. krusei) is naturally
resistant to antifungal drugs, especially fluconazole
[21, 26, 27]. In addition, itraconazole resistance rates
of C. glabrata and P. kudriavzevii (C. krusei) were
reported as 77.8% (14/18) and 33.3% (3/10), 85%
(34/40) and 85.5% (53/62), and 50% (7/14) and 30%
(6/18), respectively, in other studies [23, 28, 29]. This
rate for C. albicans was presented as 15.1% (26/172),
5.4% (2/38), 28% (36/117), 12.7% (35/273), and
11.9% (18/167) in other studies [23, 28, 30, 31].
In accordance with other investigations, as
determined by MIC90 values (0.25 mg/L), voriconazole
In vitro activity against yeast species Aslani N et al.
18 Curr Med Mycol, 2019, 5(4): 14-19
was the most potent agent among the tested azole
antifungals [24, 32]. However, in the current study,
2.2% (1/46) of C. albicans isolates with a MIC value of
1 mg/L were resistant to voriconazole. On the other
hand, the current results are different from those
reported by Bhattacharjee who observed a higher
voriconazole resistance rate in C. albicans and C.
tropicalis isolates [22].
In the present study, resistance to voriconazole was
not observed at any of the non-albicans Candida
isolates. Our data are consistent with those of recent
studies performed by Badiee et al. [23] and Yenisehirli
et al. [33] reporting a similar voriconazole resistance
rate for Candida species. In a previous study,
Wisplinghoff et al. reported that 0.6% (3/478), 5.0%
(1/20), 7.6% (2/211), and 9.8% (4/123) of C. albicans,
P. kudriavzevii (C. krusei), C. parapsilosis, and C.
tropicalis were non-susceptible to voriconazole,
respectively. Furthermore, Wisplinghoff et al. reported
that 16.3% of C. glabrata isolates had high
voriconazole MIC value, which is higher than the rate
reported in other recent investigations [24, 32, 34].
Castanheira et al. showed that voriconazole
inhibited 99.7%, 99.1%, and 88.4% of the C. albicans,
C. parapsilosis, and C. tropicalis of the isolates,
respectively. In addition, Castanheira et al. reported
that voriconazole (MIC50/90= 0.25/0.25 μg/mL) was
active against all 49 C. krusei isolates [25]. In our
previous study performed in Iran, the resistance rates
of C. albicans strains to fluconazole, itraconazole, and
voriconazole were obtained as 9.1%, 11.3% and 9.1%,
respectively [35]. In another study, we reported
fluconazole, itraconazole, and voriconazole resistance
rates of 10%, 72.5%, and 37.5% for C. glabrata
isolates, respectively [36].
No breakpoint has been mentioned for
posaconazole in the CLSI M27-S4 reference [14]. In
this study, the highest posaconazole MIC90 value was
observed against C. albicans, C. glabrata, P.
kudriavzevii (C. krusei), and C. parapsilosis (1 µg/ml).
This was reported as 2 µg/ml in other studies [28, 37,
38]. In a study performed by Wisplinghoff et al.,
posaconazole MIC50 and MIC90 values against C.
glabrata were higher than former reports [24]. Similar
to other studies, voriconazole and posaconazole had
greater activities against most Candida species in
comparison to fluconazole [33, 39].
Conclusion
With the growth of resistant yeast species to routine
antifungal agents, the selection of the most appropriate
antifungal agent and effective treatment is a critical
issue in clinical practice. According to the results of
the present study, voriconazole with a low resistance
rate might be used as the drug of choice for the
treatment of the infections occurring as a result of
Candida species. Regarding this, it is required to
perform further studies in each region to determine the
antifungal susceptibility patterns of yeast species for
the successful treatment of patients with Candida
infection.
Acknowledgments
We would like to thank the Deputy of Research of
Fasa University of Medical Sciences, Fasa, Iran, for
their financial support (grant no. 93210).
Authors contribution
M. H. A. and T. S. conceived the study. M. H. A.,
S. A., and M.R. A. prepared the strains. M. H. A. and
M. R. A. performed experiments. N. A. and M. H. A.
prepared the manuscript. N. A., M. H. A., Y. Gh., A.
K. J., and T. S. analyzed the data and edited the final
article. All authors read and approved the final
manuscript.
Conflicts of interest
The authors of the present study declare no
conflicts of interest.
Financial disclosure
This research was financially supported by the Fasa
University of Medical Sciences in Fasa, Iran (grant no.
93210).
The authors declare no financial interests related to
the materials of this study.
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... 2016). Some of the most important strains of Candida that cause candidiasis are C. albicans, C. glabrata, C. kefyr, C. guilliermondii, C. parapsilosis, C. lusitaniae, C. intermediate, C. haemulonii, and C. auris (Magaldi et al., 2004;Aslani et al., 2019). ...
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Within the limited antifungal armamentarium, the azole antifungals are the most frequent class used to treat Candida infections. Azole antifungals such as fluconazole are often preferred treatment for many Candida infections as they are inexpensive, exhibit limited toxicity, and are available for oral administration. There is, however, extensive documentation of intrinsic and developed resistance to azole antifungals among several Candida species. As the frequency of azole resistant Candida isolates in the clinical setting increases, it is essential to elucidate the mechanisms of such resistance in order to both preserve and improve upon the azole class of antifungals for the treatment of Candida infections. This review examines azole resistance in infections caused by C. albicans as well as the emerging non-albicans Candida species C. parapsilosis, C. tropicalis, C. krusei, and C. glabrata and in particular, describes the current understanding of molecular basis of azole resistance in these fungal species.
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Background and Purpose: The incidence of fungal infection as well as candidemia has increased significantly, contributing to morbidity and mortality in the developed countries. The alarming increase in infections with multidrug resistant bacteria is due to overuse of a broad spectrum antimicrobials, which leads to over growth of Candida spp.; thus, enhancing its opportunity to cause the disease. A shift has been observed in the relative frequency of each Candida spp. Antifungal agents available for the treatment of systemic and invasive candidiasis are restricted to polyenes, allylamines, azoles, and the recent echinocandin class of molecules. In the past few decades, the incidence of resistance to antifungal treatment of Candida spp. has increased rapidly, which is of serious concern for healthcare professionals. Studies on prevalence of infections and antifungal susceptibility testing can help with deciding on clinical strategies to manage this problem. Herein, we aimed to identify the epidemiology of Candida spp. among blood culture isolates and to investigate the susceptibility pattern of these species to antifungal agents. Materials and Methods: Candida spp. were isolated from blood cultures from 70 patients in a tertiary care hospital, Kolkata, India. The growth of Candida spp. on sabouraud dextrose agar was confirmed by Gram staining, where grampositive budding fungal cells were observed. The species identification as well as antifungal susceptibility testing were performed with VITEK 2 compact automated system using VITEK-2 cards for identification of yeast and yeast-like organisms (ID-YST card). Antifungal susceptibility testing was carried out with VITEK 2 fungal susceptibility card (AST-YS07) kit. Results: Out of 70 samples, Candida albicans were isolated from 34 (48.57%) samples. The remaining 36 (51.43%) were non-albicans Candida (NAC). Out of 34 C. albicans, antifungal susceptibility was detected in 28 isolates, all of which were sensitive to fluconazole (FLC). Resistance to amphotericine B (AMP), flucytosine (5FC), voriconazole (VRC), and itraconazole (ITC) was observed in 44.12%, 52.94%, 8.82%, and 17.65% of the cases, respectively. For other Candida spp. (other than C. albicans), antifungal susceptibility was evaluated for 36 isolates, among which resistance to AMP, FLC, 5FC, VRC, and ITC was found in 30.56%, 61.11%, 33.33%, 19.44%, and 38.89% cases, respectively. Conclusion: Species-level identification of Candida and their antifungal sensitivity testing should to be performed to achieve better clinical result and to select an appropriate and effective antifungal therapy. High resistance to antifungal agents is an alarming sign to the healthcare professionals.
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Background and Purpose: Candida albicans is the most common agent of candidiasis. Management of candidiasis depends on the immune status of the host, severity of disease, and the choice of antifungal drug. Antifungal drugs, specifically triazoles, widely are utilizing for the treatment of invasive fungal infections. The aim of this study was to evaluate the in vitro susceptibility of C. albicans isolates to fluconazole, itraconazole, voriconazole, amphotericin B, caspofungin. Materials and Methods: A total of 44 clinical strains of C. albicans isolated from 36 patients, were collected from hospitalized patients at four hospitals at Mazandaran province, and the in vitro antifungal susceptibility testing was performed using based on CLSI methods. Results: Generally, 34 isolates were susceptible to all of five antifungal drugs, while four isolates showed susceptible or susceptible dose dependent (SDD) and six isolates were SDD or resistance to these antifungal drugs. The lowest MIC with 0.016 µg/ml was for amphotericin B and the highest MICs for fluconazole (16 µg/ml). The lowest MIC50 (0.063 µg/ml) was related to itraconazole and the lowest MIC90 (0.25 µg/ml) to Caspofungin, so the highest MIC50 (1 µg/ml) and MIC90 (4 µg/ml) to fluconazole. The four isolates were resistance to both fluconazole and voriconazole, separately, and five isolates were resistance to itraconazole. Caspofungin showed potent activity against more than 95% C. albicans isolates. Conclusion: Overall, we reported 9.1% resistance to FLZ and VRZ, 11.3% to ITZ and AMB and 4.6% to CAS. Our finding is in agreement with previous observations that C. albicans isolates that develop resistance, because some antifungal drugs such as fluconazole widely used as prophylaxis. Keywords: In vitro susceptibility testing, Candida albicans, antifungal drugs
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Background: Prophylactic and therapeutic uses of antifungal agents have given rise to a significant shift to more resistant non-albicans Candida species associated with fungal infections. Objectives: This study aimed at identifying the distribution and antifungal susceptibility patterns of non-albicans Candida spp. isolated from clinical specimens in Tokat, Turkey. Methods: The authors determined the susceptibility of 103 non-albicans Candida isolates to the following antifungal agents: amphotericin B, anidulafungin, caspofungin, fluconazole, ketoconazole, itraconazole, voriconazole, and posaconazole, using the Etest method. Interpretation of susceptibility was carried out using species specific breakpoints suggested by the Clinical and Laboratory Standards Institute (CLSI) M27-S4 document. Results: The most frequently isolated non-albicans Candida species were Candida kefyr (44 isolates, 42.8%) followed by C. tropicalis (36 isolates, 35%), C. parapsilosis (17 isolates, 16.5%), C. glabrata (four isolates, 3.8%) and C. famata (two isolates, 1.9%). None of the strains had MIC values of > 2 µg/mL for amphotericin B except three of the 44 C. kefyr isolates. Resistance to caspofungin and anidulafungin were not detected in C. tropicalis, C. parapsilosis, and C. glabrata isolates. Only two of the 36 C. tropicalis isolates were categorized as intermediate resistant to anidulafungin, according to the new CLSI criteria. None of the C. parapsilosis isolates were found to be resistant to azole drugs. Conclusions: Most of the non-albicans Candida species were found to be susceptible to tested antifungal drugs. Therefore, use of routine antifungal agents like amphotericin B and fluconazole, which are available in this region, are suggested.
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Salt-resistant yeast strains are highly demanded by industry due to the exposure of yeast cells to high concetrations of salt, in various industrial bioprocesses. The aim of this study was to perform a physiological and transcriptomic analysis of a salt-resistant Saccharomyces cerevisiae (S. cerevisiae) mutant generated by evolutionary engineering. NaCl-resistant S. cerevisiae strains were obtained by ethyl methane sulfonate (EMS) mutagenesis followed by successive batch cultivations in the presence of gradually increasing NaCl concentrations, up to 8.5% w/v of NaCl (1.45 M). The most probable number (MPN) method, high-performance liquid chromatography (HPLC), and glucose oxidase/peroxidase method were used for physiological analysis, while Agilent yeast DNA microarray systems were used for transcriptome analysis. NaCl-resistant mutant strain T8 was highly cross-resistant to LiCl and highly sensitive to AlCl3. In the absence of NaCl stress, T8 strain had significantly higher trehalose and glycogen levels compared to the reference strain. Global transcriptome analysis by means of DNA microarrays showed that the genes related to stress response, carbohydrate transport, glycogen and trehalose biosynthesis, as well as biofilm formation, were upregulated. According to gene set enrichment analysis, 548 genes were upregulated and 22 downregulated in T8 strain, compared to the reference strain. Among the 548 upregulated genes, the highest upregulation was observed for the FLO11 (MUC1) gene (92-fold that of the reference strain). Overall, evolutionary engineering by chemical mutagenesis and increasing NaCl concentrations is a promising approach in developing industrial strains for biotechnological applications.