Candida spp are ubiquitous dimorphic yeasts that can exist as 2- to 5-|im round-oval cells called blastospores, which reproduce by budding. They have the ability to produce pseudohyphae, which are filamentous processes elongating from the cells. Fifty years ago, these round vegetative cells were considered nonpathogens. Some Candida spp, especially Candida albicans, exist as normal flora on skin and in the lower gastrointestinal (GI) tract and female genital tract. However, therapeutic and technological advances in medicine have enabled these yeasts to become true pathogens, especially in the immunocompromised hosts. In addition to causing insignificant and mild mucocutaneous infections in the normal host, these yeasts cause invasive and life-threatening disease affecting almost any organ.
Of the 200 Candida spp, C. albicans has been the most common, accounting for about 60-80% of neonatal infections. Other Candida spp that act as human pathogens include Candida tropicalis, Candida pseudotropicalis, Candida lipolytica, Candida krusei, Candida guilliermondii, Candida parapsilosis, Candida lusitaniae, Candida globrata, and Candida stellatoidea.
There are reports that infections in low birth weight infants caused by other Candida spp, such as C. parapsilosis, have increased. C. parapsilosis accounted for 29-60% of blood isolates in neonatal intensive care units, including one large multicenter study that demonstrated 60% prevalence between 1991 and 1995 (1-3). C. parapsilosis and C. albicans account for 90% of Candida blood isolates in low birth weight infants. C. parapsilosis appears to be less virulent than C. albicans because of its inability to produce phagocytosis-resistant pseudohyphae and its poor adherence and penetration of human endothelium. The mortality rate in one study from C. albicans was 26% compared to 4% from C. parapsilosis (1,2).
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