Geoffrey R. Tompkins

The Effects of Dietary Ferric Iron and Iron Deprivation on the Bacterial Composition of the Mouse Intestine

The influence of dietary ferric iron on the intestinal microbiota of mice was investigated with a view to promoting benign lactic acid bacteria (which have minimal iron requirements) in order to enhance colonization-resistance potential. Three groups of eight mice received a diet differing only in iron content, for a period of 12 weeks. Dietary iron deprivation resulted in overall increased small intestinal bacterial populations, including lactic acid bacteria, but these differences were generally not significant (p > 0.05). With the exception of coliforms, all examined bacterial groups (anaerobes, micro-aerophiles, lactobacilli, and enterococci) were significantly (p < 0.05) elevated in the colons of iron-deprived mice. The relatively low numbers of total anaerobes in the colons of iron-replete and iron-overloaded mice suggested that, as well as promotion of bacteria under iron-deprived condition, provision of ferric iron suppressed bacteria, probably by oxidation of normally reduced environments.

Competence-Dependent Bacteriocin Production by Streptococcus gordonii DL1 (Challis)

The production of streptocins STH(1) and STH(2) by Streptococcus gordonii DL1 (Challis) is directly controlled by the competence regulon, which requires intact comR and comAB loci. The streptocin (sth) locus comprises two functional genes, sthA and sthB. Whereas STH(1) activity requires sthA alone, STH(2) activity depends on both genes.

Porphyromonas gingivalis endotoxin affinity for dental ceramics

This study evaluated the effects of chemical composition, surface treatment, and initial exposure dose on Porphyromonas gingivalis lipopolysaccharide adherence to and elution from dental ceramics. Lipopolysaccharide, commonly known as endotoxin, can initiate a variety of biologic responses. Opaque, body, and Dicor ceramic disks were individually exposed to 250, 1000, or 2500 EU/ml 3H-lipopolysaccharide and incubated for 24 hours at 37 degrees C. Disks were then transferred to fresh lipopolysaccharide-free water and incubated for up to 96 hours to evaluate elution. Mean initial lipopolysaccharide adherence ranged from 0.397 +/- 0.048 EU/mm2 to 5.056 +/- 0.117 EU/mm2. Greater initial exposure levels resulted in greater adherence, and at higher lipopolysaccharide exposure levels, lipopolysaccharide adherence differences were based on ceramic type. Mean lipopolysaccharide elution levels ranged from 0.063 +/- 0.02 EU/mm2 to 0.00 EU/mm2 at 96 hours for all groups. Greater initial adherence resulted in greater elution. Ceramic type did not affect elution. Surface finish affected elution at the 2500 EU exposure level. The affinity of lipopolysaccharide for dental ceramics could contribute to a periodontal inflammatory process.

Genotypic comparison of bacteria recovered from human bite marks and teeth using arbitrarily primed PCR.

Aims:  This study assessed, for forensic purposes, the feasibility of genotypically matching oral streptococci recovered from recent human bite marks with those from the teeth of the biter.

The Butterfly Effect: An Investigation of Sectioned Roots

INTRODUCTION The butterfly effect is an optical phenomenon seen in some sections of tooth roots. The aim of this work was to investigate the density of dentinal tubules in mesiodistal and buccolingual cross-sections of roots exhibiting the butterfly effect and to determine if the effect is featured throughout the length of roots and is age related. METHODS Thirty extracted single-rooted teeth were allocated to the following groups according to patient age: group 1: 15-24 years, group 2: 25-44 years, and group 3: 45 years and over. The teeth were decoronated, and their roots were embedded in acrylic and cut into ten 1 mm-thick cross-sections. Sections were viewed under a light microscope and coded (1 or 2) according to presence or absence of the butterfly effect. A root scored 20 when all levels exhibited the butterfly appearance. The 2 teeth with the highest score from each group and 2 control teeth with the minimum score (of 10) were selected. Two adjacent, consecutive cross-sections were chosen with the most coronal cut mesiodistally and the other buccolingually. Scanning electron micrographs (×850) were taken of the central portion of their canal lumina and the density of the dentinal tubules determined. RESULTS The butterfly effect was found at all levels in the roots of the affected teeth. The tubule density was highest in the buccolingual root sections (45,348 mm(-2)) and lowest mesiodistally (12,605 mm(-2)), a significant difference (P = .02). This trend was found across all age groups. CONCLUSIONS Root sections with the butterfly effect have a lower density of dentinal tubules mesiodistally corresponding to the wings of the butterfly. The pattern was observed in teeth from all age groups and was absent in controls.

PCR-based detection of salivary bacteria as a marker of expirated blood

Distinguishing between bloodstains caused by a spatter pattern or by expirated blood may be crucial to a forensic investigation. Expirated blood is likely to be contaminated with saliva but current techniques have limited sensitivity, especially with small bloodstains. We report that a PCR assay, designed to detect salivary bacteria, can amplify streptococcal DNA from saliva stains applied to fabrics for at least 62 days after seeding. Bacterial DNA was detected when 0.01 microl of saliva was present in the stain and the amplification was not affected by contamination with blood. These findings indicate that PCR amplification of salivary microbial DNA may have application in the identification of expirated bloodstains in forensic case-work.

Effect of treatment concentration on lipopolysaccharide affinity for two alloys

OBJECTIVE This study compared gram-negative bacterial lipopolysaccharide (LPS) adherence to and elution from a Type III gold and a Ni-Cr-Be alloy using Escherichia coli LPS. METHOD One-half of the specimens of each alloy were pre-treated with 500 micrograms non-radiolabeled E. coli LPS for 24 h at 37 degrees C. All disks were then incubated with 0.15, 15 or 150 micrograms radiolabeled E. coli LPS for 24 h at 37 degrees C. To evaluate radiolabeled LPS elution, specimens were transferred to LPS-free water and incubated for 24 h at 37 degrees C. The elution scheme, which consisted of 24 h incubations and subsequent transfer to new LPS-free water, continued for up to 96 h total elution. Radiolabeled LPS adherence and elution was determined through liquid scintillation spectrometry. Control disks not treated with LPS were evaluated throughout the study with an enzymatic assay to ensure that extraneous LPS contamination did not occur. A multifactor ANOVA (p = 0.05) was used to evaluate differences in adherence to alloy specimens based upon alloy type, pretreatment status and [3H]LPS concentration. A repeated measures analysis ANOVA (p = 0.05) was used to evaluate differences in elution patterns among groups over time. Least square means were compared in case of significant effects. RESULTS Toxin uptake at each treatment concentration was significantly different from the other treatment concentrations. In addition, significantly greater amounts of [3H]LPS eluted from the non-pretreated Ni-Cr-Be alloy following the 0.15 and 15 micrograms radiolabeled [3H]LPS treatment, whereas no difference in elution was found among experimental groups following the 150 micrograms [3H]LPS treatment. SIGNIFICANCE E. coli LPS, an LPS type representative of enteric bacteria common to the gingival sulcus, has differing affinities for the alloys. This affinity difference could influence periodontal inflammatory processes, thereby resulting in differing tissue responses adjacent to dental restorations fabricated from these materials. The interaction of other LPS types with these alloys could differ.

Bacteriocin-like Inhibitory Activity Associated with Beta-hemolytic Strains of Streptococcus salivarius

Seven beta-hemolytic Streptococcus salivarius isolates produced bacteriocin-like inhibitory activity in deferred antagonism tests using a set of nine indicator bacteria (I1-I 9). 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 16, 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-, 16-, 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 I 2, 15, and 16 (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.

Incidence and Characterization of Anti-microbial Effects Produced by Actinomyces viscosus and Actinomyces naeslundii

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% (wlv) 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.

Porphyromonas gingivalis lipopolysaccharide affinity for two casting alloys

With the exception of plaque, the affinity of biologically active bacterial products for restorative materials and the influence of that affinity on periodontal health has not been detailed. This study recognized that Porphyromonas gingivalis endotoxin, which is cell envelope lipopolysaccharide (LPS) produced by a bacterium that is common to the crevicular microbial flora, has an affinity for dental casting alloys. Regardless of surface finish, no difference in LPS initial adherence or elution was recorded between a type III gold or nickel-chromium-beryllium alloy (p > 0.05), but LPS readily adhered and remained attached to both alloys. LPS affinity could contribute to periodontal inflammation in tissues that approximate restorations fabricated from either alloy.