Candida albicans is a commensal fungus, but circumstantially it may cause superficial infections of the mucous membranes, such as denture stomatitis, when a biofilm is formed on the surface of dental prostheses. This study evaluated the cell viability of C. albicans biofilms against the antifungal activity of thymol when compared with miconazole, by the fluorescence imaging using SYTO 9 and propidium iodide dyes, and counting of colony forming units. C. albicans standard strains (ATCC 11006) were used. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of drugs were determined by broth microdilution tests and the inoculum was standardized to match 0.5 on the McFarland scale (10 6 cfu/mL). Biofilms were grown on the surface of acrylic resin disks in parallel flow chambers from Sabouraud broth supplemented with 10% dextrose. For counting of colony forming units, the fungal solution was sequentially diluted and plated in Sabouraud dextrose agar. Data were analyzed using two-way ANOVA and Tukey's test (a=5%). Biofilms treated with thymol and miconazole presented low numbers of viable cells at the evaluated exposure times. There was statistically significant difference (p<0.05) when compared with control, and the mean value of the exposure times between miconazole and thymol did not differ significantly (p>0.05). In conclusion, both drugs have similar efficiency as antifungal agents against biofilms of C. albicans formed on acrylic surfaces.
ResumoThe surfaces that come into contact with foods are important sources for the transmission of microorganisms in food processing environment. Many pathogenic bacteria are able to form biofilm in food-contact surfaces remaining viable even after cleaning procedures. The capability of S. aureus to form biofilms enhances it survival in food processing environments providing a physiological advantage as etiological agent of foodborne diseases. This study assessed the ability to form biofilm of S. aureus (n=57) isolates from food-contact surfaces of food processing environments of hospitals in the city of João Pessoa, Paraíba, Brazil. The biofilm formation was evaluated in tryptone soy broth after 48 h of incubation in polystyrene microtiter plates using crystal violet staining and its quantification was based on the difference between the optical density (OD) measurements of the test and negative control samples (ΔOD 492 nm ). The isolates were classified as strong (4x OD control < OD), moderate (2x OD control < OD ≤4x OD control ), weak (OD control < OD ≤ 2x OD control ) or none (OD ≤ OD control ) biofilm-producing. The strains S. epidermidis ATTCC 12228 and S. aureus ATTCC 25923 were used as negative and positive (strong producer) control for biofilm formation, respectively. Among the S. aureus biofilm-producers ΔOD 492 nm values ranged from 0.217 to 0.881. Two
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