Jundishapur Journal of Microbiology (2009); 2(1): 1-6 1
Invasive candidiasis; a review article
Majid Zarrin1, Ali Zarei Mahmoudabadi1,2
1Department of Medical Mycoparasitology, School of Medicine, and 2Infectious and Tropical
Diseases Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
Received: March 2009 Accepted: March 2009
The epidemiology of Candida fungal infections is growing, due to the increasing size of
the people at risk. Candida species are the fourth main cause of bloodstream infections;
however, significant geographic differences have been reported. Although, in some
instances, these changes may be related to medical interventions, such as the use of
antifungal agents in prophylaxis, in the majority of cases, they seem to be a consequence
of changes in the host, such as more-severe immunosuppression or different types of
immunosuppression impacting both risk periods and the infections that occur.
Discussion of surveillances and reports will be critical to improve our understanding of
the importance of invasive Candida infections, and to facilitate the prioritization of the
investigation as well as the prevention efforts.
Keywords: Candidiasis, Invasive candidiasis, Candida albicans
The epidemiology of invasive fungal
infection has changed during the last two
decades. The frequency of the disease has
increased, and the population of patients at
risk has expanded to include those with an
extensive list of medical conditions, such as
solid organ and hematopoietic stem cell
transplantation (HSCT), receipt of
immunosuppressive therapy, human
immunodeficiency virus (HIV) infection,
premature birth, advanced age, surgery and
cancer . Moreover, the etiology of
invasive mycoses has also changed. In the
1980s, yeasts (mainly Candida albicans)
were the most frequent causative agents of
invasive fungal infections. Despite of its
benefits, medical development has led to a
susceptible population with suppressed
immunological defenses against fungal
infection. These factors heighten the risk for
many invasive fungal infections, including
candidiasis, aspergillosis, cryptococcosis,
and mucormycosis .
Epidemic of HIV is a major factor that
has contributed to a remarkable increase in
the frequency of invasive candidiasis. Before
the extensive use of highly active anti-
retroviral therapy (HAART) in developed
countries, 80% of HIV-infected patients
developed mucosal candidiasis, while others
developed cryptococcosis, pneumocystosis
and other lethal mycoses, for example,
penicilliosis [2,3]. Candidiasis, a main cause
of death in patients with leukemia and solid
organ transplants or recipients of stem cell,
is currently observed more frequently among
patients in intensive care units (ICUs). The
species of Candida causing infection are
more diverse. C. albicans is the most
frequent pathogen followed by C. glabrata,
C. tropicalis and C. parapsilosis.
Jundishapur Journal of Microbiology (2009); 2(1): 1-6 2
Candida invasive infections
Bloodstream infection by Candida species
(candidemia) is the most frequent clinical
manifestation of invasive candidiasis, and is
a significant cause of morbidity and
mortality in hospitalized patients. Candida
species are the fourth most widespread cause
of hospital-acquired bloodstream infections
in the United States [4-5], with a frequency
of 1.5 cases per 10,000 patients days . In
a comparable European survives, the
frequency is slightly lower, at 0.5-0.7 cases
per 10,000 patients days [7-10]. Currently,
the highest reported incidence of healthcare
related candidemia (3.7 cases per 10,000
patients days) comes from an eleven-center
sentinel observation plan in Brazil .
While the reasons for this high rate of
infection are not obvious, several factors
could be involved, including the availability
of less resources for medical care and
training programs, difficulties in the
achievement of infection control programs
in hospitals of developing countries, limited
numbers of health-care staffs, and less
effective practices of antifungal drug
treatment in high-risk patients.
Candidemia is usually connected with
infection outside of bloodstream. In
numerous patients the yeast spreads from the
gastrointestinal tract to other organs and this
helps to elucidate why Candida bloodstream
infection is similar to a devastating disease.
In the United States, the mortality rate for
candidemia in medical centers from1997 to
2001 was 49% , which was 11% higher
than that detected in the same hospital from
1983 to 1986 . Analysis of the
epidemiological researches that evaluates the
varying incidence of Candida bloodstream
infection over time is complicated.
However, it is necessary to find important
dissimilarities in the results coming from
various countries or various centers.
In the Netherlands, the incidence rate of
candidemia among hospitalized patients rose
from 0.37 to 0.72 cases per 10.000 patient
days between 1987 and 1995 . But in
Switzerland, the rate remains approximately
permanent between 1991 and 2000 (median
incidence: 0.5 cases per 10,000 patient days)
. In Iran 45% of kidney recipients and
84% of liver recipients had Candida
colonization in different sites of their bodies
. A research in Iran showed that
disseminated candidiasis was the second
common cause of invasive fungal infections
. In the past years, the main groups at
risk for serious Candida diseases were cases
that were neutropenic, had received
transplants, or had been treated with
cytotoxic or corticosteroids drugs. At
present, the patients who are in the ICU, are
the most susceptible to show severe Candida
infections. The most high risk patients are
those who have a central venous catheter,
are receiving patenteral nutrition or are on
broad-spectrum antibiotics and have high
Acute Physiology and Chronic Health
Evaluation scores [17-19]. The fourth most
frequent cause of nosocomial bloodstream
infection among ICU patients is Candida
species. Moreover, these yeasts are the third
most widespread cause of nosocomial
bloodstream infections . The mortality of
candidemia remains about 40% .
There are now approximately 200 species of
Candida, but only a few have been involved
in human infection. Ninety percent of all
Candida bloodstream infection globally
have been caused by five species: C.
albicans, C. glabrata, C. parapsilosis, C.
tropicalis, and C. Krusei [6,9,11,20]. The
remaining diseases have been caused by
several other Candida, including C.
dubliniensis, C. famata, C. guilliermondii,
C. lusitaniae, C. norvegnesis, C. pelliculosa,
and C. rugosa [9,11,20,21]. Though these
species are unusual causes of candidiasis,
some of them are recognized to happen in
nosocomial clusters, or display innate, or
even obtained resistance to antifungal drugs
Candida albicans remains the
predominant cause of candidemia
worldwide. The frequency of invasive
Jundishapur Journal of Microbiology (2009); 2(1): 1-6 3
candidiasis which is recovered from blood
samples varies according to geographical
setting, and demographics of the population
studied. Broad use of fluconazole for
treatment of HIV-infected cases with
persistent oropharyngeal candidiasis resulted
in the selection of Candida species
essentially less sensitive to azoles in the
early 1990s. The azole-drug resistant strains
in these patients emerged because of
acquisition of resistance with previously
sensitive strains of C. albicans . This
occurrence has led to the concern that
extensive fluconazole use in broader patient
populations could cause related selections
for species and strains that possess inherent
or acquired azole resistance. Nevertheless,
the frequency of fluconazole resistance
among C. albicans bloodstream isolate,
gathered in population-based and sentinel
surveillance programs worldwide, stays
A new trend noted in numerous
hospitals is an enhancement in the frequency
of C. glabrata as serious Candida infections
[25,26]. There are some reasons for this
increase, including the living habitat, age
and type of the patients, and use of
fluconazole. C. glabrata is usually noted in
persons older than 60 years  and in
patients who have leukemia or received a
stem cell transplant, and those who are
associated with increasing use of
fluconazole . The significance of this
epidemiologic trend is that C. glabrata is
frequently resistant to fluconazole, the drug
used most often for the treatment of
candidemia. Though candidemia is the main
type of invasive candidiasis, broad visceral
invasion with Candida can happen by
persistently negative blood cultures. Almost
all organs can be infected, although the
kidneys, eyes, liver, spleen, and brain are
most frequently involved. Signs of invasive
infection that ought to be clinically
diagnosed are endophthalmitis or
chorioretinitis as well as the emergence of
painless skin lesions.
The patients with confirmed candidemia or
invasive candidiasis must be treated with an
antifungal drug . The elevated rate of
spreading to main organs, once Candida
obtains entrance to the bloodstream, offers
the basis for this approach. There are
primarily two goals in the treatment of
candidiasis, interference with Candida
proliferation in the body and the reduction of
the factors providing favorable environment
for growth of Candida.
Several antifungal drugs are available
for the treatment of candidiasis. These
consist of fluconazole, voriconazole,
caspofungin, amphotricin B, and lipid
formulations of amphotricin B. Studies
confirm that fluconazole, caspofungin, and
voriconazole are as valuable as amphotricin
B deoxycholate in the treatment of
candidemia . Fluconazole is the
preferred treatment of candidemia.
Fluconazole is effective against most species
of Candida. The drug has been revealed to
be as useful as amphotricin B in
nonneutropenic patients. Nevertheless,
fluconazole has restricted activity against C.
glabrata and is not effective against C.
krusei. Combination therapy may be used to
cope with treatment failures [30-34].
Doctors should become aware of the most
frequent species of Candida causing
bloodstream invasive infection at their
centers. Vascular catheter removal enhances
the clearance of Candida from the blood
. Daily blood culture is required to
confirm that the problem of fungemia is
resolved, and treatment must continue for
two weeks following the date of the primary
negative blood culture.
The disease is very difficult to diagnose
because some of the etiologic agents of
disease are also commonly observed in
healthy people. As a result, laboratories have
an important role in detection of diseases
and identification of etiologic agents of
them. In addition, they can help with the
Jundishapur Journal of Microbiology (2009); 2(1): 1-6 4
selection and the monitoring of antifungal
therapy. Information that is essential for
laboratory workers is as follows; the clinical
history of patients, occupation, the source of
the samples, any prior treatment with
antifungal, anti-microbial and immuno-
suppressive drugs, the method by which the
samples were collected and types of
The patients must not take any
antifungal drugs three days before sampling.
For urinary sampling, 10 ml of midstream or
catheter specimens should be collected in a
sterile test tube. Cerebrospinal fluid (CSF)
samples provide good specimens for patients
with candidal meningitis. CSF are usually,
collected by a clinician using a routine
lumbar puncture technique. In candidemia
20 ml of blood from adults or 1-5 ml from
children is collected and directly inoculated
into the blood culture medium (Biphasic
medium). Suitable specimens for respiratory
candidiasis are early morning sputum and
bronchial washing collected in a sterile
screw-cap container. The samples should be
digested by KOH or N-acetyl cysteine or
pancratein before preparing smears and
cultures. Another method for sampling from
candidiasis is biopsy from organs.
Direct examination of specimens and
observation of fungal elements in clinical
materials is a very important part of
laboratory diagnosis. As a result, a correct
report can help the clinician prescribe
suitable treatment. Furthermore, in acute
diseases, such as Candida meningitis and
systemic candidiasis in AIDS patients, rapid
direct microscopy can play a very important
role in suitable treatment. For liquid
specimens, such as urine, saliva, sputum,
and CSF, firstly, centrifuge and then
microscope slides can be prepared from their
sediments. The microscope slides should be
stained by Gram, Giemsa or methylene blue
stains. Tissue sections should be stained
using Periodic Acid Schiff, Grocott’s
methenamine silver or Gram stain. Ovoid
yeast cells, budding cells (3-7m in
diameter), true hyphae, pseudohyphae or
both are the morphological forms of
Candida species that are usually seen in
clinical materials. Positive direct microscopy
from a biopsy or a sterile site, such as blood,
CSF and vitreous and joint fluid, are
significant, whether of yeast or
pseudohyphae. According to Talwar et al.
 the presence of mycelial forms of
Candida in direct microscopy is as a
diagnostic marker for candidiasis; however,
when C. glabrata is the etiologic agent of
disease, pseudohyphae is not be observed in
All clinical materials are cultured on the
suitable culture medium. There are a number
of culture media for isolation of Candida
species from clinical materials but the
selective medium most often used is
Sabouraud’s dextrose agar (SDA) with
chloramphenicol or other anti-bacterial
agents. Many species of Candida (C. krusei,
C. parapsilosis and C. tropicalis) are
sensitive to cycloheximide, which is why
media with cycloheximide should not be for
isolation of Candida species. SDA is
recommended for isolation and culture of
Candida species. CHROMagar Candida is a
new medium that is used for isolation and
identification of some clinically important
Candida species. The incubation
temperature for cultures is 30-37C for 24-
72 h (37,38).
Invasive candidiasis is recognized as a cause
of infection with increased incidence in the
past two decades. This expected increase
reflects several factors, such as changes in
hosts at risk and progress in diagnostic
methods. The appearance of Candida with
variable susceptibilities to antifungal agents
emphasizes the clinical importance of
establishing fungal diagnoses. Changes in
hosts sensitive to Candida infection,
diagnostic approaches, practice patterns, and
probable changes in climatic influences, will
possibly continue to amend the
epidemiology for years to come.
Jundishapur Journal of Microbiology (2009); 2(1): 1-6 5
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Address for correspondence:
Majid Zarrin, Department of Medical
Mycoparasitology, School of Medicine, Ahvaz
Jundishapur University of Medical Sciences,
Tel: +98611 3330074; Fax: +98611 3332036