Enhancement of secretory aspartyl protease production in biofilms of Candida albicans exposed to sub-inhibitory concentrations of fluconazole.

The production of Secretory Aspartyl Proteases (Sap) is an important virulence factor of Candida albicans. Many studies have shown that a challenge with sub-inhibitory concentrations of antifungals lead species of Candida to the secretion of higher concentrations of Sap. Nevertheless, published studies only reported the secretion of such enzymes by cells growing in planktonic phase, with few mention of biofilms. The present study evaluated the alterations in the secretion of Sap by C. albicans grown in biofilms and exposed to sub-inhibitory concentrations of fluconazole. The MICs for fluconazole of seven clinical strains were determined for planktonic cells. Biofilm and planktonic cells were grown in the presence of ½ MIC, » MIC, and no medication (control). The relative metabolic activity, indirectly related to cell loads, were estimated by the absorbance of reduced XTT and the Sap activity was evaluated by bovine albumin test. It was observed that 72 h-old biofilms under the influence of ½ MIC had fewer cells than » MIC and control. The production of Sap was inversely proportional to the cell content, with higher secretion in ½ MIC, followed by » MIC and control. Biofilms of C. albicans challenged by sub-MICs of fluconazole tend to secrete higher quantities of Sap.

Time-related increase of staphylococci, Enterobacteriaceae and yeasts in the oral cavities of comatose patients.

BACKGROUND/PURPOSE: The composition of oral microbiota in comatose patients remains uncertain. Some pulmonary pathogens may be found in dental biofilms or as part of the saliva microbiota. It is supposed that some pneumopathogenic microorganisms may overgrow in the mouths of comatose patients and spread to their lungs. METHODS: The oral colonization dynamics of staphylococci, Enterobacteriaceae and yeasts in nine comatose patients (group 1), and in 12 conscious patients that brushed their teeth at least twice a day (group 2) was evaluated. Both groups were followed up for 7 days after hospitalization. Daily samples of saliva were obtained, dispersed and plated on selective culture media and colony forming units of each microbial group were obtained. RESULTS: For patients in group 1, the counts of total viable bacteria, staphylococci, Enterobacteriaceae and yeasts progressively increased in a time-dependant manner. For the conscious patients of group 2, there was no increase. CONCLUSION: It would appear that concomitant consciousness and brushing teeth are determinants in controlling the selected pneumopathogen counts in resting saliva. The increase in microbial counts in comatose patients is understandable because these microorganisms could spread to the lungs.

Proposal of a low-cost protocol for colorimetric semi-quantification of secretory phospholipase by Candida albicans grown in planktonic and biofilm phases.

Biofilms are aggregates of microorganisms living in multilayered structures inside polymeric matrices onto surfaces. These biofilms may subvert the physiological properties of adjacent tissues causing morphofunctional failure. Many studies have shown that the expression of virulence attributes is maximized when microbes form such communities. This study evaluated the differential phospholipasic activity of Candida albicans SC5314 grown in planktonic phase and in biofilm. We propose two distinct protocols for the colorimetric evaluation of phosphatidylcholine hydrolysis in neutral and acidic conditions. The results showed that both protocols are suitable for the proposed intention and that 72 h-old planktonic cultures of C. albicans SC5314 secrete higher quantities of neutral (6.42-fold) and acidic (3.85-fold) phospholipases than biofilms.