Bacteriocins as Factors in the In Vitro Interaction Between Oral Streptococci in Plaque

Abstract

The effect of bacteriocins on the composition of dental plaque flora was studied in vitro with bacterial plaque formed by oral streptococci on glass rods suspended in broth medium. Cell-free preparations containing mutacin SW31, a bacteriocin produced by Streptococcus mutans , killed sensitive cells present in the plaque selectively, but did not affect resistant cells. Similar preparations from a non-bacteriocinogenic mutant exerted only a slight effect. Mixed growth of bacteriocin-producing S. mutans SW31 with the sensitive S. sanguis Ny101 resulted in a nearly single-strain plaque of the former. Mutacin could be detected in the plaque substance as well as in the surrounding medium. A non-bacteriocinogenic mutant, which was shown not to be altered in functions affecting growth in plaque, allowed substantial growth of S. sanguis Ny101. Sequential inoculation of the bacteriocinogenic plaque former S. sanguis P3A3 and the sensitive S. mutans OMZ61 showed that the cells of the latter are killed rapidly in established plaques when inoculated with the bacteriocinogenic strain. A trypsin-sensitive antagonistic substance could be detected in the plaque, but not in the surrounding medium. The results indicate that bacteriocins can be active in plaque in vitro and suggest that bacteriocins could play a role in determining the composition of plaque in vivo.

Effect of Bacteriocin Production by Streptococcus mutans on the Plaque of Gnotobiotic Rats

“…Microorganisms. The following strains of S. mutans were used: T2 (7); T2 bac-, a non-bacteriocinogenic mutant isolated after treatment of the parent strain with N-methyl-N'-nitro-N-nitroso-quanidine (Aldrich) (8); and SW31 (12) and its corresponding mutant, SW31 bac.…”

“…These findings suggested that bacteriocins may play a role in modifying the plaque microflora. Recent in vitro experiments with a strain of S. mutans and a corresponding bac mutant have strengthened such a view (12).…”

A Review Escherichia coli and the Human Gut: Some Ecological Considerations

“…The consistent failure to demonstrate the actions of colicins in vivo probably results from their inactivation by proteases (Kelstrup & Gibbons 1969). More recent work suggests that bacteriocin activity is of great importance for organisms colonizing solid surfaces (Weerkamp et al 1977) especially in the mouth (Van der Hoeven & Rogers 1978. Indeed, the majority of the evidence supporting the selective advantage of colicin activity comes from observations of extra-intestinal environments (Konisky 1978).…”

Inverse correlation between the proportion of salivary bacteria inhibiting Streptococcus mutans and the percentage of untreated carious teeth

“…Another observation indicating that mutacins have relatively little effect in the oral cavity is that both tnutacinogenic and sensitive strains can be isolated from the same dental plaque (16). This observation, and the fact that mutacins are seldom detected in liquid cultures (2,16,(20)(21)(22)(23)(24)(25), is probably an indication of a relatively restrained distatice over which they tnay act (26,27). Many in vivo experiments in humans and animals indicate that certain tnutacins decrease the number of S. tnutans in dental plaque and reduce the amount of caries (28-33), thus demonstrating a protective role for mutacins in the dental plaque ecosystem.…”