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Candida species
are yeast forms that are ubiquitous in nature and frequent colonizers
of the skin and mucous membranes in humans, although they rarely
cause invasive disease in immunocompetent individuals. Only a small number
of the more than 150 species of Candida that have
been described are considered to be pathogenic. Candida
albicans remains the most frequent cause of human candidiasis, but
infections owing to other species of Candida are
increasingly recognized.1-4 In addition, the incidence
of infections owing to C albicans isolates that
are resistant to azole antifungals is increasing. This changing
epidemiology has implications for appropriate treatment of antifungal-resistant Candida infections.
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Non-albicans species known to cause human disease
include C glabrata, C guilliermondii, C
keyfr (formerly C pseudotropicalis), C
krusei, C lusitaniae, C parapsilosis,
and C tropicalis. Candida parapsilosis is
the non-albicans species isolated most commonly
in children, and in some neonatal units has surpassed C
albicans as the most commonly isolated Candida species.1,4-8 Clinicians should be aware of echinocandin resistance
with C parapsilosis. Candida glabrata is
the second most commonly isolated species in adults, which also
has important implications for treatment, as C glabrata exhibits
variable resistance to azole antifungals. Candida tropicalis may
be an emerging pathogen in immunocompromised hosts, in whom it is
associated with significant morbidity and mortality.9
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The incidence of colonization with Candida spp
depends upon host characteristics such as age and overall health.
Neonates are frequently colonized with Candida spp,
and localized oropharyngeal candidiasis (thrush) is not uncommon
in this population. Hospitalized and ill children are more frequently
colonized than are healthy children. Candida spp
have relatively low virulence factors compared to other organisms,
and therefore rarely cause disease in the normal host. For candidiasis
to occur, the host must have impaired resistance to disease, the
number of yeast organisms must be high, or both.
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Neonates and pregnant women have impaired host resistance to Candida species,
as do patients with immunodeficiencies (congenital or acquired),
induced immunosuppression (eg, owing to chemotherapy or corticosteroids),
or debilitation (owing to trauma or surgery). Advances in health
care that have decreased mortality for many conditions (eg, prematurity
and malignancy) have been associated also with changes in host defense
and normal flora, which have in turn led to a larger population
at risk for invasive Candida infection. Preterm
newborns and oncology patients frequently receive multiple and long-term courses
of medications, particularly antimicrobials (altering the normal
flora), and have defects in mucosal or skin barriers (eg, owing to
intravascular catheters), which puts them at high risk for development
of candidiasis.
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In recent years, Candida species have become increasingly
important causes of health-care-associated infections. Most health-care-associated
pediatric fungal infections are candidemias, and these are most
frequently diagnosed in children in neonatal and surgical intensive
care units. The source of transmission in these cases is frequently
unclear, although recent studies using molecular diagnostics have ...