Attachment of
Bacteroides melaninogenicus
subsp.
asaccharolyticus
to Oral Surfaces and Its Possible Role in Colonization of the Mouth and of Periodontal Pockets
Authors: Slots Jörgen , Gibbons Ronald J. 
Published: January 2020

This investigation examined the ability of cells of
Bacteroides melaninogenicus
subsp.
asaccharolyticus
381 to adhere to surfaces that might be important for its initial colonization of the mouth and its subsequent colonization in periodontal pockets. Of 48 asaccharolytic strains of
B. melaninogenicus
, 47 agglutinated human erythrocytes, whereas none of 20 fermentative strains, which included reference cultures of the subspecies
intermedius
and
melaninogenicus
, were active. Electron microscopy indicated that both asaccharolytic and fermentative strains possessed pili; hence, the presence of pili did not correlate with the hemagglutinating activities of
B. melaninogenicus
strains. Both asaccharolytic and fermentative
B. melaninogenicus
strains suspended in phosphate-buffered saline adhered in high numbers to buccal epithelial cells and to the surfaces of several gram-positive bacteria tested, including
Actinomyces viscosus, A. naeslundii, A. israelii, Streptococcus sanguis
, and
S. mitis. B. melaninogenicus
subsp.
asaccharolyticus
381 also attached, but in comparatively low numbers, to untreated and to saliva-treated hydroxyapatite. Addition of clarified whole saliva to suspensions of strain 381 almost completely eliminated adherence to buccal epithelial cells and to hydroxyapatite surfaces, but saliva had no detectable effect on attachment to gram-positive plaque bacteria. Both fermentative and nonfermentative strains of
B. melaninogenicus
also attached in high numbers to crevicular epithelial cells derived from human periodontal pockets, but normal human serum strongly inhibited attachment. Serum also inhibited attachment of strain 381 to saliva- and serum-treated hydroxyapatite, but it had little effect upon attachment to gram-positive bacteria. These observations suggested that salivary and serum components would strongly inhibit the attachment of
B. melaninogenicus
cells to several oral surfaces, but not to the surfaces of certain gram-positive bacteria commonly present in human dental plaque. This was confirmed by an in vivo experiment in which streptomycin-labeled cells of
B. melaninogenicus
381-R were introduced into the mouths of two volunteers. After 10 min, several hundred-fold higher numbers of the organism were recovered from preformed bacterial plaque present on teeth than from clean tooth surfaces or from the buccal mucosa and tongue dorsum. High numbers of
B. melaninogenicus
cells were also recovered from preformed plaque after 150 min, but virtually no cells of the organism were recovered from the other surfaces studied. These data suggest that the presence of dental plaque containing
Actinomyces
and other gram-positive bacteria may be essential for the attachment and colonization of
B. melaninogenicus
cells after their initial introduction into the mouth. Similarly, the presence of subgingival plaque containing gram-positive bacteria may be necessary for its secondary colonization in periodontal pockets.