An Epifluorescence Technique for Studying the Adherence of Oral Bacteria to Buccal Epithelial Cells

Abstract

Methods currently in use to measure bacterial adherence to exfoliated buccal epithelial cells are unsuitable for small poorly staining bacteria. An epifluorescence technique was developed, therefore, using acridine orange in pH 3·3 citrate/sodium hydroxide buffer which permitted good visualisation of the smallest test bacteria when attached to buccal cells. In addition, a novel method for standardising bacterial suspensions by relating total counts of bacteria deposited on filters to optical density measurements was used. The adherence properties of a total of eighteen fresh and type strains (including bacterial species implicated in the pathogenesis of periodontal disease and species regarded as members of the normal commensal flora) were measured using these methods. Approximately half of the strains tested adhered well to buccal cells, including fresh isolates of Bacteroides gingivalis, Veillonella species, Streptococcus salivarius and Streptococcus sanguis. Adherence did not correlate in all cases with the known distribution of these species in vivo, although the fresh strains correlated more closely and adhered in higher numbers than the type strains.