THE ISOLATION AND IDENTIFICATION OF BACTEROIDES SPP. FROM THE NORMAL HUMAN GINGIVAL FLORA

Abstract

GRAM-NEGATIVE anaerobic bacilli are important members of the normal flora of the mouth (Hardie and Bowden, 1974) and are implicated in a variety of oral infections (Hardie, 1974). The mouth consists of several micro-environments with different microbial flora; the gingival crevice and dental plaque are the principal sites of colonisation by gram-negative anaerobic bacilli (Socransky and Manganiello, 1971; Hardie and Bowden, 1974). The surface of the tongue is almost devoid of Bacteroides, and saliva contains a variable number of fusobacteria derived from the gingival crevice (Hadi and Russell, 1968; 1969). Gibbons et al. (1963, 1964) and Loesche, Hockett and Syed (1972) found that 16.1% of the cultivable flora of the human gingival crevice, 4% of the flora from dental plaque in normal subjects, and 17% of the plaque flora in institutionalised subjects, were gram-negative anaerobic rods; Loesche and Gibbons (1965) devised a scheme for their identification. Bacteroides melaninogenicus was first described in studies of the microflora of mucous membranes (Oliver and Wherry, 1921); pigmented strains constitute 4.8% of the cultivable flora of the normal gingival crevice (Gibbons, 1974) and 5.6% of the plaque flora from institutionalised subjects (Loesche et al., 1972). Loesche, Socransky and Gibbons (1964) isolated non-pigmented strains that they called B. oralis; this species shares many properties with some strains of B. melaninogenicus and is the subject of an unresolved taxonomic debate (Holbrook and Duerden, 1974; Sundqvist, 1976; Holbrook, Duerden and Deacon, 1977; International Committee, 1977, 1979; Duerden et al., 1980). The B. melaninogenicus/oralis group also includes human isolates of B. rumini-cola and two recent non-pigmented additions, B. bivius and B. disiens (Holdeman and Johnson, 1977). In the present investigation, conventional bacteriological methods for the isolation (Holbrook, Ogston and Ross, 1978) and identification (Duerden et al., 1976, 1980) of gram-negative anaerobic bacilli were used to assess the occurrence of the different species in the normal flora of the gingival crevice of healthy adults.