Enhanced susceptibility of Candida albicans to chlorhexidine under anoxia

Aim: Periodontal pockets can be colonized not only by bacteria, but also by Candida albicans. However, its role in periodontitis is unknown. This study evaluated the inhibitory performance of chlorhexidine digluconate under normoxic and anoxic conditions against 16 strains of C. albicans from periodontal pockets and other 20 from the oral mucosa. Methods: Strains were grown in normoxia and anoxia to adapt themselves to the different atmospheric conditions. Microdilution-based assays were carried out to determine the minimum concentrations of chlorhexidine that may restrain the conditioned candidal strains, in normoxia (normoxic MIC) and anoxia (anoxic MIC). The Mann-Whitney U test was used to evaluate the antimicrobial effect of chlorhexidine on C. albicans under normoxic and anoxic conditions (α = 0.05). Results: The normoxic MIC of chlorhexidine varied broadly from 150 to 1200 μg/mL, whereas its anoxic MIC varied narrower from 2.34 to 37.5 μg/mL. Regarding the origins of strains, no statistically significant differences (p > 0.05) were found. Conclusions: These results indicate that anoxic environmental conditions, compatible with periodontal pockets, tend to enhance C. albicans susceptibility to chlorhexidine.published_or_final_versio

Proposal of protocols using D-glutamine to optimize the 2,3-bis (2-methoxy-4-nitro-5-sulfophenly)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide (XTT) assay for indirect estimation of microbial loads in biofilms of medical importance

Due to technical problems, biofilm biomasses are difficult to be precisely determined. One reliable strategy is based on the colorimetry of formazan compounds derived from tetrazolium salt reduction. XTT presents some desirable properties that make the biofilm measurements easier. However, cells entrapped within the extracellular matrixes normally do not metabolize the tetrazolium equally, leading to underestimation of cell contents. This study evaluated the effectiveness of D-glutamine, a plerotic substrate of tricarboxilic acid cycle (TAC), as inducer of KIT reduction. The metabolic activities of aerobic and anaerobic 48 h-old monospecific biofilms of Pseudomonas aeruginosa ATCC (R) 27853 (TM). Klebsiella pneumoniae ATCC (R) 13883 (TM). Staphylococcus epidermidis ATCC (R) 12228 (TM). Streptococcus mutans ATCC (R) 25175 (TM), and Candida albicans SC5314 were evaluated. Results showed that D-glutamine 50 mM (for P. aeruginosa, K. pneumoniae, and S. epidermidis) and 25 mM (for S. mutans and C albicans) may enhance the detection of soluble formazan in a significant manner, what becomes the XTT reduction assay more robust. (C) 2011 Elsevier B.V. All rights reserved.84229930