In vivo colonization of salivary pellicle by Haemophilus, Actinomyces and Streptococcus species

Eight human subjects with healthy oral conditions were examined to study developing dental plaque. Supragingival plaque, buccal mucosa, tongue dorsum and saliva were sampled prior to the pumicing and cleaning of facial surfaces of the four upper premolars and two first molars. Samples were processed anaerobically on media that were selective for the oral Streptococcus spp., Haemophilus spp., and Actinomyces spp., as well as supplemented blood agar for identification of gram-negative bacterial groups and total cultivable flora. NAD-requiring Haemophilus spp., Streptococcus sanguis, Streptococcus mitis, Streptococcus mutatis and Streptococcus salivarius were found in most oral samples. Analysis of the distribution of the Actinomyces spp., Actinomyces viscosus, Actinomyces naeslundii and Actinomyces odontolyticus, in oral samples prior to teeth cleaning, found no significant differences between proportions or prevalence of these species in saliva, buccal mucosa, tongue, or pooled plaque samples. All three species were found on most surfaces in all subjects. Following cleaning, plaque was allowed to develop for 48 h. Proportions of a species in 2-hour plaque, when higher than proportions in the same individual's saliva samples, were interpreted to be due to a species promotion by salivary pellicle (as 2-hour plaque from cleaned teeth). A median ratio of 1: 3 of saliva versus 2-hour plaque was seen for A. odontolyticus suggesting some promotion by pellicle. A. viscosus and S. sanguis showed median ratios of saliva: 2-hour plaque of 1: 6 or higher, suggesting that salivary pellicle strongly promoted these species' adherence. Developing plaques contained high proportions of streptococci, especially S. sanguis and S. mitis. as well as Haemophilus parainflueniae. Significant increases were seen in proportions of S. sanguis in 48-hour versus 24-hour, and 2-hour plaques. A. viscosus, A. naeslundii and A. odontolyticus were found in most developing plaque samples and in similar proportions to each other. A significant twofold increase in proportions of A. odontolyticus, and fourfold increase of S. sanguis, was seen in 48- versus 2-hour plaques suggesting growth of these species. Forty-eight-hour plaque was composed primarily of Facklam type 1 S. sanguis and this species was found in significantly higher proportions than S. salivaritts or S. mutans. NAD-requiring haemophili were found in high proportions and comprised 99% of the haemophili in 48-hour plaque. Although A. naeslundii was not dectected in as many 48-hour samples as A. viscosus or A. odoniolyticus, these three species were found in similar proportions in 48-hour developing plaque samples.