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Mutans streptococci (MS) are known to be causative agents of dental caries. It has been suggested that these cariogenic bacteria could be eliminated from dental plaque by application of bacteriocins or bacteriocin-like inhibitory substances (BLIS). In the present study 272 bacterial strains of the genera Streptococcus, Enterococcus and Staphylococcus were tested for their production of BLIS activity against MS by use of a deferred antagonism test on agar media supplemented with either whole blood or yeast extract. Although only 14.3% of the test strains displayed anti-MS activity, the inhibitory agents produced by these strains were characterised by considerable diversity in the range of their inhibitory action against both MS and other common oral streptococcal species. It is suggested that combinations of relatively specifically targeted anti-MS BLIS may have potential application to the prevention of dental caries. [ABSTRACT FROM AUTHOR]

Samples of subgingival plaque from 67 children, 5-7 years of age, were examined for the presence of certain suspected periodontal pathogenic species using the conventional technique of anaerobic sonification, dilution and spiral plating. When this technique was compared with a direct plating procedure which involved no preliminary dispersion and dilution of plaque specimens, it was found that the direct method resulted in double the frequency of children in whom black- pigmented Bacteroides (BPB) were detected and a 10-times increase in the number of subjects harbouring Actinobacillus actinomycetemcomitans. Samples from the tongue, tonsils and saliva were also plated using the direct technique. BPB were detected less commonly in the plaque specimens (61.3% of children) than in saliva (89.5%), or on the tongue (86.6%) and tonsils (97.1%). Expressed as percentages of a pooled sample of the total BPB population, the most frequently detected species in plaque were Bacteroides intermedius (44.4%) and Bacteroides melaninogenicus (48.0%). The most prevalent isolate in all other oral sites was B. melaninogenicus. Expressed as percentages of children in whom BPB were detected, the most frequently isolated species from plaque using the conventional dilution technique was B. insermedius (21.3%), whereas other BPB species were present in fewer than 5% of children. Fusobacterium nucleatum and Capnocytophaga species were isolated most frequently from plaque but were also commonly detected in the various other oral sites. [ABSTRACT FROM AUTHOR]

Thirty strains of V. anguillarum were tested for the production of inhibitory substances against closely-related bacteria using the deferred antagonism test. Only one strain. Vibrio anguillarum VL4355, inhibited strains of V. ordalii and this effect was blocked by the addition of iron salts to the culture medium. Siderophore production was investigated for this strain. Results from bioassays suggested that strain VL4355 produced a siderophore related to anguibactin, the plasmid-encoded phenolate siderophore produced by V. anguillarum strain 775. However, when plasmid DNA was compared for strains 775 and VL4355 the BamHI-generated restriction profiles were different, although hybridization experiments indicated some homology. Using the chrome-azurol sulphate assay to measure siderophore production, strain VL4355 yielded significantly higher values than other V. anguillarum strains. Amberlite XAD-2 was used to produce concentrated siderophore preparations from strains VL4355 and 775. Both preparations were inhibitory to the growth of strains of V. ordalii, but not V. anguillarum, as were solutions of the iron chelator ethylenediamine-di(o-hydroxyphenylaectic acid). The difference in sensitivity to iron-limiting conditions for V. ordalii and V. anguillarum, coupled with the inability of V. ordalii to utilize ferric-anguibactin, could reflect different mechanisms of iron uptake for these two organisms. [ABSTRACT FROM AUTHOR]

Sheep from a broken-mouth periodontitis-affected farm were classified into three groups according to degree of severity of periodontal destruction. Subgingival plaque samples were collected from 10 animals in each group, as well as from 10 sheep from a periodontitis-free farm, and were plated anaerobically onto a variety of selective and non-selective media. Results show that several different suspected periodontopathic microorganisms commonly associated with human periodontitis are also present in the plaque of sheep. Black-pigmented Bacteroides were associated with the severely-affected category but there were no significant differences between less severely-affected groups and healthy animals. This suggests either that sampling may not have coincided with periods of activity in these sheep or that other bacteria may be involved in the initiation of the disease. Type II Fusobacterium nucleatum was associated with all disease categories when compared to healthy animals. [ABSTRACT FROM AUTHOR]

Samples of subgingival plaque were obtained from healthy and broken-mouth periodontitis-affected sheep. Deeper pockets were found in affected sheep and these were associated with increased levels of asaccharolytic, black-pigmented Bacteroides (BPB) species, including trypsin-positive BPB similar to B. gingivalis. It is suggested that these organisms could have a similar role in the pathogenesis of periodontal disease in sheep to that proposed for BPB in certain human periodontal diseases. [ABSTRACT FROM AUTHOR]

Seven beta-hemolytic Streptococcus salivarius isolates produced bacteriocin-like inhibitory activity in deferred antagonism tests using a set of nine indicator bacteria (I1 -I9). Five of these S. salivarius strains (KWF, TOVE-R, K17, K21, and K26) were inhibitory to indicators I2, I5, I6, and I7. Mutated non-hemolytic derivatives showed concomitant loss of inhibitory activity against I2, I5, and I6, but retained activity against I7. Inhibitory activity against I2, I5, and I6 was restored in beta-hemolytic revertants of such mutants. Strain 3638 was inhibitory to all of the indicator organisms except I3, and this pattern of inhibitory activity was retained by non-hemolytic derivatives. It appeared that strain 3638 produced an additional broadly-active inhibitory agent, since a mutant (strain 3638A), which was apparently defective in the production of this inhibitor, retained both the beta- hemolytic and I2-, I5-, I6-, and I7-inhibitory activities. Non-hemolytic derivatives of strain 3638A were inhibitory only to I7. Strain 3638, therefore, appeared to produce at least three inhibitory agents: one active only on I7; another acting on I2, I5, and I6 (and associated with beta-hemolytic activity); and a third apparently active on all of the indicators other than I3. S. salivarius strain JH inhibited all nine indicator strains and possessed a beta-hemolytic character which differed from that of the other strains in being readily eliminated on treatment with the plasmid-curing agent novobiocin. Non-hemolytic derivatives of JH retained inhibitory activity against the complete set of indicators. The results of this study suggest that hemolysin production by some S. salivarius strains may be intimately associated with a distinctive type of bacteriocin-like activity. [ABSTRACT FROM AUTHOR]

Sixty-two facultative Actinomyces strains isolated from dental plaque were tested for the production of bacteriocin-like inhibitory effects by a deferred antagonism method. When incubated anaerobically, all isolates produced identical inhibitory patterns against 15 indicator organisms, but under microaerophilic conditions, little inhibitory activity was observed. Activity was not evident after anaerobic incubation on a medium buffered by 0.5% (w/v) calcium carbonate. Gas-liquid chromatographic analyses of agar blocks removed from the inhibitory zones indicated that, compared with microaerophilic conditions, anaerobic incubation encouraged production of high concentrations of lactic and succinic acids, and the concomitant fall in the pH was probably responsible for the inhibitory effects. [ABSTRACT FROM AUTHOR]