Characterisation of microbial adherence to epithelial cells following biocide treatment by analysis of area under the frequency distribution curve

Abstract

The aim of this study was to further characterise the anti-adherence effects of certain antimicrobial agents by evaluating their effects on the frequency distribution of Candida albicans blastospores (MEN strain) to buccal epithelial cells (BEC). A light microscopic assay was employed to evaluate the effects of super- and sub-minimal inhibitory concentrations of chlorhexidine gluconate, dequalinium chloride, cetrimide and cetylpyridinium chloride on candidal adherence in vitro. Frequency distributions were plotted to describe the adherence profile of each treatment and mathematical descriptions of these distributions were performed by calculating the areas under the frequency distribution curves (AUC). Comparison of the AUC of each treatment and control (sterile water treatment) was performed using a one-way analysis of variance. Each concentration of all antimicrobial agents significantly reduced the AUC. These reductions were due to greater percentages of BEC showing lower numbers (zero, one, two) of adherent blastospores and also lower percentages of BEC showing higher numbers of adherent blastospores in comparison to control. Generally, the anti-adherence effects of these antimicrobial agents (as measured using AUC determinations) were greater following treatment of blastospores and were observed with both super- and sub-minimal inhibitory concentrations. These findings suggest a greater affinity of the antimicrobial agents for the blastospore surface and also a greater ability to block, either directly or indirectly via steric hinderance, adhesins on the blastospore surface than receptors on the surface of BEC. It is suggested that to fully appreciate the anti-adherence potential of antimicrobial agents, the frequency distribution of microbial adherence data should be considered, as this will provide information on specific adherence population shifts, in conjunction with their effects on the mean number of adherent microorganisms per epithelial cell. In addition, the anti-adherence activity observed for the antimicrobial agents examined indicates their potential use in the prophylaxis of superficial candidal infections in the oral cavity.