THE ISOLATION OF ACTINOMYCES-NAESLUNDII FROM SOUND ROOT SURFACES AND ROOT CARIOUS LESIONS

The isolation of Actinomyces naeslundii from sound, exposed root surfa ces (n = 56) and soft and leathery root carious lesions (n = 71) was i nvestigated, Root carious lesions were sampled after the removal of ov erlying plaque. Supragingival plaque or carious dentine was sampled us ing a sterile excavator, the samples were disaggregated and cultured o n both selective and non-selective media. A. naeslundii isolates were identified to the genospecies using specific antisera. Significantly g reater numbers and proportions of ri. naeslundii genospecies 2 than A. naeslundii genospecies 1 were isolated from all sites sampled, There was no significant difference between the numbers and proportions of t he two genospecies isolated from leathery and soft lesions, The relati onship between the presence of A. naeslundii genospecies and aciduric and acidogenic organisms was investigated. Those sound exposed root su rfaces from which A. naeslundii genospecies 1 and/or 2 were isolated y ielded significantly lower numbers of lactobacilli and yeasts than the surfaces from which A. naeslundii were not isolated. This difference was also found in leathery lesions but not soft root carious lesions. The microflora of soft root carious lesions was found to comprise prim arily gram-positive pleomorphic rods which formed 70+/-7.8% of the flo ra, while in plaque from exposed root surfaces and in infected dentine from leathery lesions the gram-positive pleomorphic rods represented only 35% of the flora.