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Abstract
Biofilms are microbial communities that form on a surface and are surrounded by extracellular polymeric substances. Candida biofilms are a cause of infections associated with medical devices. In the present study, an attempt was made to evaluate a significance of biofilm formation ability (BF) in virulence of C. albicans. C. albicans of 98 isolates, 24 commensal strains obtained from the oral cavities of healthy volunteers, 29 from blood culture, 25 from urine culture, and 20 from vaginal candidiasis, were assayed for BF, an ability to adhere to epithelial cells (ADH), cell surface hydrophobicity (CSH), and germ tube forming rate (GT). The relationships of BF with CSH, ADH, and GT were statistically examined. A positive correlation between BF and ADH was obtained, but the correlation (r=0.326) was relatively low. To assess BF as a factor contributing for candidiasis, mice lethality test was performed. The 10 isolates with the highest BF (mean survival rate, 24%) allow to kill mice more than those with the 10 lowest BF (mean survival rate, 47%). In addition, clinical strains isolated from blood culture, urine culture, and vaginal candidiasis showed higher BF than oral commensal strains. These results suggest BF may represent a virulent characteristic of C. albicans.
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Figure 1.
Correlation between the ability of biofilm formation (BF) and putative virulence factors of C. albicans. A. Correlation between BF and relative cell surface hydrophobicity: r = 0.219, p = 0.07; B. Correlation between BF and the ability of adherence to HeLa cells: r = 0.326, p < 0.01; C. Correlation between BF and germ tube forming rate: r = 0.045, p = 0.61.
Figure 2.
Effect of C. albicans BF on lethality in mice. The 10 isolates with the highest BF and the 10 isolates with the lowest BF were tested. Twenty mice per Candida isolate were injected intravenously via tail vein with a total of 0.2 ml normal saline containing 5 × 105 cells. High BF-C. albicans (mean survival day: 25 days, mean survival rate: 24%) allow to kill mice more than low BF-C. albicans (mean survival day: 40 days, mean survival rate: 47%) (p < 0.01). • represents a survival rate of one isolate tested.
Figure 3.
Difference in BF among different C. albicans isolates. Commensal strains (n = 24) isolated from the oral cavities of healthy carrier and clinical isolates from blood culture (n=29), urine culture (n = 25), and vaginal candidiasis (n = 20) were assayed for BF. XTT activities were measured colorimetrically at 490 nm with microtiter plate reader. Each bar represents the mean from three independent experiments (p < 0.01). Error bars mean standard deviations.
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