Distribution of Actinobacillus actinomycetemcomitans in localized juvenile periodontitis plaque: an electron immunocytochemical study.

Abstract

The use of an indirect electron immunocytochemical labelling procedure for labelling Actinobacillus actinomy cetemcomitans (serotype b) in ultrathin sections of pure bacterial cultures and in localized juvenile periodontitis‐derived plaque is described. Optimal labelling was obtained after fixation with 2.5% glutaraldehyde, embedding in glycol methacrylate and labelling with highly diluted absorbed rabbit anti‐A. actinomycetemcomtians γ‐globulin followed by incubation with diluted goat anti‐rabbit γ‐globulin conjugated with horseradish peroxidase. and subsequent histochemical visualization of the peroxidase. These labelling conditions were used to determine that no cross reactions existed with commonly found plaque bacteria. Two of 5 labelled plaque specimens were positive for this A. actinamycetemcomitans serotype. In one specimen large numbers of labelled bacteria were located only in the most apical portion of the plaque layer. In another specimen labelled cells were scattered throughout the plaque. Control experiments using normal rabbit γ‐globulin were all negative.