Detection of Actinobacillus actinomycetemcomitans and Bacteroides gingivalis in subgingival smears by the indirect fluorescent‐antibody technique

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Abstract
An indirect immunofluorescence technique for the detection of Actinobacillus actinomycetemcomitans (A. actinomycetemcomitans) and Bacteroides gingivalis (B. gingivalis) in smears of subgingival plaque was evaluated. The assay used species‐specific rabbit antibodies against A. actinomycetemcomitans (3 serotypes) and B. gingivalis (1 serotype) and a goat anti‐rabbit IgG fluorescein conjugate. Of 88 periodontal specimens studied, about 80% were either positive or negative for the two species by both culture and immunofluorescence, about 5% revealed the organisms by culture but not by immunofluorescence, and about 13% were culture‐negative and immunofluorescence‐positive. In positive lesions, immunofluorescence tended to yield higher A. actinomycetemcomitans counts than culture and culture tended to yield higher B. gingivalis counts than immunofluorescence. In a periodontal treatment study including 21 adult patients and 73 deep periodontal pockets, A. actinomycetemcomitans or B. gingivalis were detected by immunofluorescence in 5 of 8 periodontal lesions which showed loss of probing periodontal attachment after therapy but not in any of 37 treated periodontal sites exhibiting probing attachment gain. It was concluded that indirect immunofluorescence can detect A. actinomycetemcomitans and B. gingivalis in subgingival plaque and that monitoring these organisms may aid in differentiating progressing and nonprogressing periodontitis lesions.