Biofilm formation by Candida dubliniensis.
Candida dubliniensis is an opportunistic yeast closely related to Candida albicans that has been recently implicated in oropharyngeal candidiasis in human immunodeficiency virus-infected patients. Most manifestations of candidiasis are associated with biofilm formation, with cells in biofilms displaying properties dramatically different from free-living cells grown under normal laboratory conditions. Here, we report on the development of in vitro models of C. dubliniensis biofilms on the surfaces of biomaterials (polystyrene and acrylic) and on the characteristics associated with biofilm formation by this newly described species. Time course analysis using a formazan salt reduction assay to monitor metabolic activities of cells within the biofilm, together with microscopy studies, revealed that biofilm formation by C. dubliniensis occurred after initial focal adherence, followed by growth, proliferation, and maturation over 24 to 48 h. Serum and saliva preconditioning films enhanced the initial attachment of C. dubliniensis and subsequent biofilm formation. Scanning electron microscopy and confocal scanning laser microscopy were used to further characterize C. dubliniensis biofilms. Mature C. dubliniensis biofilms consisted of a dense network of yeasts cells and hyphal elements embedded within exopolymeric material. C. dubliniensis biofilms displayed spatial heterogeneity and an architecture showing microcolonies with ramifying water channels. Antifungal susceptibility testing demonstrated the increased resistance of sessile C. dubliniensis cells, including the type strain and eight different clinical isolates, against fluconazole and amphotericin B compared to their planktonic counterparts. C. dubliniensis biofilm formation may allow this species to maintain its ecological niche as a commensal and during infection with important clinical repercussions.
Ramage
G
G
Department of Microbiology, Division of Infectious Diseases, The University of Texas Health Science Center at San Antonio, San Antonio, Texas 78245, USA. ribot@uthscsa.edu
Vande Walle
K
K
Wickes
B L
BL
López-Ribot
J L
JL
D017088:AIDS-Related Opportunistic Infections / Q000382:microbiology; D000935:Antifungal Agents / Q000494:pharmacology; D018441:Biofilms / Q000254:growth & development*; D002175:Candida / Q000187:drug effects / Q000254:growth & development* / Q000502:physiology; D002180:Candidiasis, Oral / Q000382:microbiology; D006801:Humans; D018613:Microscopy, Confocal; D008954:Models, Biological; D010949:Plasma / Q000502:physiology; D019904:Polymethyl Methacrylate; D011137:Polystyrenes; D012463:Saliva / Q000502:physiology
D000935:Antifungal Agents; D011137:Polystyrenes; D019904:Polymethyl Methacrylate