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Origin of the Names of Species of Candida
Simi Vincent, M.D., Ph.D.
The selected name of a microorganism is binomial, comprised of the generic name followed by a species name that is subject to the International Code of Botanical Nomenclature (ICBN) (1,2). The names are derived from Latin or Greek. They are descriptive of the fungus, the source of its isolation, or the name of a person. Name changes usually result from differences in taxonomic opinions and are often confusing and controversial. Yeasts and yeastlike organisms are the most common fungi isolated in clinical laboratories (3). They are considered opportunistic pathogens. The name Yeast is derived from words that mean foam and rise. Hence yeasts are often thought of as fermentative Ascomycetes. Some yeasts are Basidiomycetes with a vegetative state and predominantly reproduce by budding or fission. The ability to produce pseudohyphae, true hyphae and/or terminal chlamydospores, the shape and arrangement of the blastoconidia and other morphologic characteristics as well as biochemical tests are used to identify yeasts at their genus and species leve (2). The genus Candida contains heterogeneous anamorphic yeasts and comprises about 196-200 species (1,4) that are physiologically related to ascomycetes or basidiomycetes. The name is derived from the custom in ancient Rome for a candidatus, a candidate for public office, to dress in white. Albico means “to be white,” so the name Candida albicans is redundant. The more important pathogenic species, Candida albicans, C. tropicalis, C. parapsilosis, C. krusei, C. lusitaniae and C. glabrata, are phylogenetically related to the Ascomycetes. The genus Candida is classified as follows: Phylum: Deuteromycota Class: Blastomycetes Order: Cryptococcales Family: Cryptococcaceae Genus: Candida
Candida albicans (Robin) Berkhout, 1923: 100 synonyms have been applied to Candida albicans. It first was called Oidium albicans by Charles-Philippe Robin (1821-1885) in 1853 (1). After further studies, Zopf in 1890 changed its name to Monilia albicans. The currrently accepted name, C. albicans, was introduced by Berkhout in 1923 (1). The names of several species of Candida have been changed. C. stellatoidea, C. claussenii and C. langeronii have been merged with C. albicans while C. dubliniensis was separated from C. albicans due to the different arrangement of the blastoconidia and the chlamydospores (2). Germ tube formation and chlamydophore formation are the two most reliable morphologic criteria for the identification of C. albicans (4). Cells of almost all clinical isolates of C. albicans are diploid (1). C. albicans is the species that is most commonly isolated from patients with nearly all forms of candidiasis.
Candida glabrata (Anderson) Meyer and Yarrow, 1978. Candida glabrata was first named Cryptococcus glabrata by Anderson in 1917. Lodder and deVries in 1938 called it Torulopsis glabrata. The original separation of the genera was based on the inability of Torulopsis sp. to produce pseudohyphae, like other species of Candida. However, this criterion appears to have been misapplied, leading to the incorrect generic name for the species glabrata (5). Meyer and Yarrow in 1978 introduced its present name. C. glabrata cells are ovoid and produce no pseudohyphae.
Candida tropicalis (Castellani) Berkhout, 1923: Aldo Castellani (1877-1971), while he worked in Ceylon (Sri Lanka), differentiated several species of Candida; including Candida tropicalis in 1910. He called it Oidium tropicale. Other names given to this species have been Monilia tropicalis, Candida vulgaris, Mycotorula dimorpha, Candida paratropicalis. 58 synonyms have been applied to C. tropicalis. Berkhout introduced the present name in 1923 (1). It is germ tube negative and does not produce chlamydospores. C. tropicalis is a diploid Ascomycetous yeast (5).
Candida parapsilosis (Ashford) Langeron and Talice, 1932: Synonyms include Monilia onychopila (Poll and Nann, 1926), Monilia parapsilosis (Ashford, 1928), Mycocandida parapsilosis (Dodge, 1935). Candida parapsilosis introduced by Langeron and Talice in 1932 is the current name of this diploid yeast. Colony morphology resembles that of C. albicans, but C. parapsilosis differs microscopically with their crooked or curved short pseudohyphae and occasional large hyphal elements called giant cells (2).
Candida krusei (Castellani) Berkhout, 1923: Castellani described C. krusei in 1910 as Sacharomyces krusei, and as Endomyces krusei in 1912 (6). Chalmers (1913) named it Monilia krusei. 18 other synonyms were proposed before Berkhout renamed it in 1923 as C. krusei. Colonies of C. krusei appear similar to C. albicans and other pathogenic Candida species on Sabouraud’s agar, but on cornmeal-Tween 80 agar C. krusei form pseudohyphae with elongated blastoconidia, giving the appearance of crossed match sticks or trees (1,2). C. krusei is inherently resistant to fluconazole.
Candida lusitaniae van Uden and do Carmo-Sousa. 1959: Dietrichson called this species Candida parapsilosis var. obtusa in 1954. In 1959 van Uen and do Carmo-Sousa named it C. lusitaniae. It was first isolated from the alimentary canals of warm-blooded animals in Portugal. Since 1979 this species has been recognized as an opportunistic human pathogen, found in blood, urine, and the respiratory tract (1). C. lusitaniae resembles C. tropicalis and C. parapsilosis, but differs in its ability to ferment cellobiose and assimilate rhamnose (2). C. lusitaniae is generally a yeast of low virulence and it may be resistant to amphotericin B (4).
References 1. Kwon-hung KJ, Bennet JE. Medical
mycology, 1992.
2. Guarro J, GeneJ, Stchigel AM.
Developments in Fungal Taxonomy. Clin Microbiol Rev 1999; 12: 454-500.
3. Larone D. Medically important fungi, 5th ed. 4. Murray PR et al. Manual of Clinical Microbiology, 1995, 6th ed. 5. Kurtzman CP, Fell JW. The Yeasts
(A Taxonomic tudy) 4th ed. Chapter 1. Definition, Classifiation and Nomenclature
of Yeasts. 6. Castellani A. Observations on the fungi found in tropical bronchomycosis. Lancet 1912; 1:13-15.
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