Biofilm-Forming Ability ofCandida albicansIs Unlikely To Contribute to High Levels of Oral Yeast Carriage in Cases of Human Immunodeficiency Virus Infection

Abstract

An increased prevalence of candidal carriage and oral candidiasis is common in cases of human immunodeficiency virus (HIV) infection, and the reasons for this may include the enhanced ability of colonizing yeasts to produce biofilms on mucosal surfaces. The aim of the present study was therefore to examine the differences, if any, in the biofilm-forming abilities of 26 Candida albicans yeast isolates from HIV-infected individuals and 20 isolates from HIV-free individuals, as this attribute of yeast isolates from patients with HIV disease has not been examined before. Biofilm formation in microtiter plate wells was quantitatively determined by both the 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide (XTT) reduction method and the crystal violet method. Although candidal biofilm formation could be quantitatively evaluated by either technique, the better reproducibility (P < 0.05) of the XTT reduction assay compared with that of the crystal violet method led us to conclude that the former is more reliable. There were no significant quantitative differences in biofilm formation between C. albicans isolates from HIV-infected patients and isolates from HIV-free individuals during in vitro incubation in a multiwell culture system over a period of 66 h. Three of eight host factors in the HIV-infected group were found to be associated with candidal biofilm formation. Thus, yeasts isolated from older individuals and those with higher CD4-cell counts exhibited decreased biofilm formation, while the findings for yeasts from individuals receiving zidovudine showed the reverse (P < 0.05 for all comparison). Our data indicate that attributes other than biofilm formation may contribute to the increased oral yeast carriage rates in cases of HIV infection.Candida biofilms have recently received considerable attention due to their high prevalence on catheter surfaces (1) and their notorious resistance to antifungals (14, 29). These characteristics of Candida biofilms are likely to contribute to both superficial (26) and systematic candidiasis (21). As candidal infections are the most common fungal infections in individuals infected with the human immunodeficiency virus (HIV) (27), we hypothesized that isolates recovered from HIV-infected individuals may have better biofilm-forming abilities than those recovered from HIV-free individuals.A number of workers have compared the adherence of Candida albicans yeast isolates from HIV-infected patients and HIV-free subjects to mucosal surfaces, as adherence to host surfaces is a prerequisite for subsequent biofilm formation and colonization (12). However, those studies have yielded variable results showing enhanced adherence to buccal epithelial cells (BECs) by yeast isolates from HIV-positive individuals (32), a comparable degree of adhesion between test and control isolates (34), and an even higher degree of adhesion by control isolates (23). To our knowledge, no group has studied the biofilm-forming abilities of Candida isolates recovered fr...

Comparison of Various Methods Used to Detect Biofilm Production of Candida Species

“…3) XTT reduction assay: -It has been used as a routine tool for the quantification of Candida biofilms [3,[7][8][9][10][11]. {XTT: (2,3-bis After the adhesion phase, the cell suspensions were gently aspirated and each well was washed twice with Phosphate Buffered Saline (PBS) [5] to remove any remaining planktonic cells, taking care not to disturb the adhered cells.…”

“…Afterwards, each well was washed four times with 350 μl of sterile distilled water and immediately destained with 200 μl of 95% ethanol. After 45 min of destaining, 100 μl of destaining solution was transferred to a new well and the destaining solution was measured with ELISA reader (Lablife ER 2007 Microplate washer, DIAGNOVA) at 595 nm [3,7].…”

Fluconazole resistance in Candida glabrata is associated with increased bud formation and metallothionein production

“…An XTT reduction assay was performed as described previously (Jin et al, 2003). Briefly, XTT (Sigma) was dissolved in PBS to a final concentration of 1 mg ml 21 .…”

Susceptibility of clinical isolates of Candida to photodynamic effects of curcumin

“…In order to evaluate whether PDT could cause the detachment of Candida biofilms from the plastic surface, the quantification of the cells adhered to the wells was performed by means of Crystal Violet (CV) assay [27]. For this purpose, additional samples from PÀLÀ and PDT groups (40 mM of CUR with 18 J/cm 2 of illumination) were included in this evaluation.…”

“…For in vitro biofilm formation, the isolates were individually inoculated in 5 ml of RPMI-1640 medium and incubated overnight in an orbital shaker (AP 56, Phoenix Ind Com Equipamentos Científicos Ltda, Araraquara, SP, Brazil) at 120 rpm, 378C, for 16 hours. After incubation, the yeast were washed twice with 5 ml of phosphate-buffered saline (PBS), and suspended to 10 7 cells/ml by adjusting the optical density of the suspension to 0.38 at 520 nm [27,28]. Aliquots of 100 ml of the standard cell suspension were transferred into each well of pre-sterilized polystyrene, flat-bottomed 96-well microtiter plates.…”