Candida dubliniensis
| Candida dubliniensis | |
|---|---|
| Scientific classification | |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Subdivision: | Saccharomycotina |
| Class: | Saccharomycetes |
| Order: | Saccharomycetales |
| Family: | Saccharomycetaceae |
| Genus: | Candida |
| Species: | C. dubliniensis |
| Binomial name | |
| Candida dubliniensis Sullivan et al. (1995) | |
Candida dubliniensis is a fungal opportunistic pathogen originally isolated from AIDS patients. It is also occasionally isolated from immunocompetent individuals. It is a dimorphic yeast of the genus Candida, very closely related to Candida albicans but forming a distinct phylogenetic cluster in DNA fingerprinting. It is most commonly isolated from oral cavities, [1] and is also occasionally found in other anatomical sites.
Prevalence and epidemiology
Candida dubliniensis is cosmopolitan (found around the world), and has been described as a separate species in 1995.[2] Retrospective studies have shown that previously it had been commonly identified as Candida albicans, with which C. dubliniensis is closely related and shares a number of characteristics.
One test for distinguishing C. dubliniensis from C. albicans, is laboratory culture of the organism at 42°C. Most C. albicans strains grow at this temperature,[3] whereas most C. dubliniensis isolates do not.[2] There are also significant differences in the conditions that lead to the formation of chlamydospores between C. albicans and C. dubliniensis, although they are otherwise phenotypically very similar.[2]
A European study of 2,589 isolates, that had originally been identified as C. albicans, revealed that 52 of them (2.0%) were C. dubliniensis. Most of these isolates were from oral or faecal specimens from HIV-positive patients, though one vaginal and two oral isolates were from healthy individuals.[citation needed] Another study in the United States surveyed 1,251 yeasts previously identified as C. albicans, and identified 15 isolates (1.2%) as C. dubliniensis. Most of these isolates were from immunocompromised individuals, such as AIDS, chemotherapy, or organ transplant patients.[citation needed] The majority of C. dubliniensis strains were recovered from respiratory, urine and stool specimens.[citation needed] The Memorial Sloan-Kettering Cancer Center also conducted several studies, both retrospective and prospective. In 974 germ-tube positive yeasts, 22 isolates (2.3%) from 16 patients were C. dubliniesis. All individuals were immunologically compromised with either malignancy or AIDS, and the isolates came from a variety of different sites. C. dubliniensis was also isolated from the mouths of 18% of patients with diabetes and who use insulin.[4]
Antifungal susceptibility
In one study, all 20 C. dubliniensis isolates tested were susceptible to itraconazole, ketoconazole and amphotericin B.[5]
Fluconazole
Many isolates of C. dubliniensis are sensitive to fluconazole. In one study, 16 of 20 isolates were sensitive to fluconazole, while four were resistant.[5] It has been hypothesized that C. dubliniensis has the ability to rapidly develop resistance to fluconazole, especially in patients who are on long-term therapy.[5]
Stable fluconazole resistance could be induced in vitro by subjecting sensitive strains to increasing concentrations of this antifungal. This resistance is mediated by a multidrug transporter that can be mobilized rapidly in vitro, on exposure to fluconazole.[citation needed]
Cases in America have also shown the emergence of fluconazole-resistant C. dubliniensis. Three isolates were discovered in Texas, two of which were resistant (MIC, 64 µg/mL), and one had dose-dependent susceptibility (MIC, 16 µg/mL). Among C. dubliniensis isolates in HIV+ patients in Maryland, most isolates were highly susceptible to fluconazole. A study of 71 isolates in Ireland, showed that both the fluconazole-resistant and susceptible strains were susceptible to itraconazole, amphotericin B, and 5-fluorocytosine (microdilution). They were also susceptible to experimental triazoles and voriconazole and echinocandin.[citation needed]
References
- ↑ Gilfillan GD, Sullivan DJ, Haynes K, Parkinson T, Coleman DC, Gow NAR (1998). "Candida dubliniensis: Phylogeny and putative virulence factors". Microbiology 144 (4): 829–838. doi:10.1099/00221287-144-4-829. PMID 9579058.
- ↑ 2.0 2.1 2.2 Sullivan DJ, Westerneng TJ, Haynes KA, Bennett DE, Coleman DC (1995). "Candida dubliniensis sp. nov.: phenotypic and molecular characterization of a novel species associated with oral candidosis in HIV-infected individuals". Microbiol. 141 (7): 1507–1521. doi:10.1099/13500872-141-7-1507.
- ↑ Kamiyama A, Niimi M, Tokunaga M,. Nakayama H (1989). "Adansonian study of Candida albicans: intraspecific homogeneity excepting C. stellatoidea strains". J Med Vet Mycol 27 (4): 229–241. doi:10.1080/02681218980000311. PMID 2677300.
- ↑ Willis AM, Coulter WA, Sullivan DJ, Coleman DC, Hayes JR, Bell PM, Lamey PJ (2000). "Isolation of C. dubliniensis from insulin-using diabetes mellitus patients". J Oral Path & Med. 29 (2): 86–90. doi:10.1034/j.1600-0714.2000.290206.x.
- ↑ 5.0 5.1 5.2 Moran GP, Sullivan DJ, Henman MC, McCreary CE, Harrington BJ, Shanley DB, Coleman DC (March 1997). "Antifungal drug susceptibilities of oral Candida dubliniensis isolates from human immunodeficiency virus (HIV)-infected and non-HIV-infected subjects and generation of stable fluconazole-resistant derivatives in vitro". Antimicrob. Agents Chemother. 41 (3): 617–23. PMC 163761. PMID 9056003.