Biomedical subjects

D Beighton

Publications and source records attributed to D Beighton.

At least 73 records · Page 4Linked to original sources

PubMed1997

Effect of use of 0.05% cetylpyridinium chloride mouthwash on normal oral flora.

OBJECTIVES: The aims of this study were to examine the effect of the use of a mouthwash containing 0.05% cetylpyridinium chloride (CPC) on (1) the composition of the normal oral microbial flora and (2) the establishment of non-oral bacterial species in the mouth. METHOD: In a double-blind study, 129 subjects used, twice daily for 6 weeks, either a randomly assigned test or placebo mouthwash. At baseline and at the completion of the study, a sample of the oral flora was obtained by asking each subject to "swish" around the mouth for 30 s, 10 ml of distilled water. The numbers of total colony forming units (CFU), facultative bacteria, streptococci, mutans streptococci, lactobacilli, staphylococci, yeasts and enterococci were enumerated after culture on eight non-selective and selective media. RESULTS: After 6 weeks use of either the test or placebo mouthwashes, there were no significant differences (analysis of variance) between the counts (CFU/ml of sample) for any of the microbial taxa. CONCLUSIONS: These data indicate that the use of a CPC-containing mouthwash does not alter the composition of the normal oral flora or result in the establishment of non-oral and potentially pathogenic bacteria in the mouth.

Analysis of Variance↗

PubMed1997

Relevance of the use of rubber dam in microbiological sampling of carious dentine.

The aim of this study was to determine the role of rubber dam isolation and the influence of salivary contamination during cavity preparation on the collection of samples of dentine for microbiological examination. Cavities were prepared in 23 carious teeth. Access to caries was gained and a sample of soft, stained demineralized tissue was taken with a round bur. After removing the rubber dam each cavity was flooded with saliva and after thorough washing and drying a second dentine sample was taken. Cavity preparation was completed and the cavity flooded with saliva. After thorough washing and drying a final sample was taken. A data set from another study served as a control for bacterial contamination at the end of cavity preparation where a rubber dam remained in place throughout. There were no significant differences in the numbers of bacteria in dentine samples gathered with and without rubber dam, which implies that salivary contamination can be removed by thorough washing and drying of the cavity.

Adult↗

PubMed1997

The effect of chlorhexidine/xylitol chewing-gum on cariogenic salivary microflora: a clinical trial in elderly patients.

The effects of 14-day use of either a chlorhexidine/xylitol or a xylitol chewing gum on salivary levels of mutans streptococci, lactobacilli, and yeasts were determined for 53 subjects (mean age 79.49 +/- 7.7 years) participating in this randomised, double-blind, placebo-controlled trial. Salivary flow rates and enamel staining were measured and the attitudes of the subjects to gum chewing were evaluated by the use of structured questionnaires. The chlorhexidine/xylitol gum significantly reduced the salivary levels of mutans streptococci (p < 0.0001) lactobacilli (p < 0.05) and yeasts (p < 0.05) while the xylitol placebo gum produced significant reductions in mutans streptococci (p < 0.01) only. The study population found chewing gum twice per day for 10 min an acceptable method of receiving medication and improving oral health. Prior to gum use participants recognised persistent symptoms of dry mouth and their subjective evaluation of dry mouth was significantly (p < 0.001) related to the number of prescribed medications with xerostomic side-effects. The desire to continue gum use was significantly related to the subjects' evaluation of their oral dryness at baseline and to their perceived oral health gain from gum usage. Only those participants with stained enamel at baseline exhibited increased enamel staining following chlorhexidine/xylitol gum usage.

Aged↗

PubMed1996

Criteria for caries removal at the enamel-dentine junction: a clinical and microbiological study.

In the UK cavity preparation at the enamel-dentine junction (EDJ) is considered complete when all soft and/or stained tissue is removed. The aim of the present work was to link the clinical criteria of dentine consistency and dentine colour with the microbiological status of the tissue. Cavities were prepared in 564 teeth. Under rubber dam, access to the EDJ was gained and the sample sites selected (n = 847). Their consistency was noted as hard or soft and wet or dry when probed. The colour of the site was noted as stain-free or stained. Dentine was sampled using a round bur. After microbiological processing the total anaerobic count and counts of mutans streptococci and lactobacilli were expressed as log10 [CFU per sample]. Soft sites harboured significantly more bacteria than hard sites (P < 0.001). Soft and wet sites harboured significantly more bacteria than soft and dry sites (P < 0.001). Stained and hard sites harboured more bacteria than stain-free and hard sites (P < 0.05) but this difference was not considered to be clinically relevant. The relatively simple clinical criteria used here correlated significantly with the microbial findings. All soft dentine must be removed at the EDJ to ensure minimal infection of the underlying hard dentine. However, it may not be necessary to continue preparation until the EDJ is also stain-free.

Adult↗

PubMed1996

Associations between dietary intake, dental caries experience and salivary bacterial levels in 12-year-old English schoolchildren.

A population of 328 12-yr-old English schoolchildren, consuming their normal diets, was investigated in a cross-sectional study to determine the interactions between caries experience, oral hygiene status as gingival index (GI), dietary intake (as number of eating events per day and the number of eating events per day at which sugar-containing foodstuffs, confectionery or starch-containing foods were consumed) and salivary levels of caries-associated micro-organisms (mutants streptococci, lactobacilli and yeasts). The mean (+/- SD) decayed, missing and filled surfaces (DMFS) (excluding precavitation lesions) score was 3.05 +/- 3.85 and 5.72 +/- 5.00 (including precavitation lesions). The DMFS scores were significantly related to the salivary levels of caries-associated micro-organisms and to the number of eating events per day for total number of eating events and the number of eating events at which sugar-containing foods or confectionery were consumed. These associations were apparent in both bivariate and partial correlation coefficients with the caries-associated micro-organisms and GI controlled. The total daily intakes of food types, except for starch, were not associated with caries experience. No significant correlations were found between intake of food types and salivary levels of caries-associated micro-organisms except that the mean number of confectionery-eating events was correlated with lactobacillus levels (r = 0.136, p < 0.01). The salivary levels of mutans streptococci, lactobacilli and yeasts were significantly correlated with GI scores. These data do not indicate simple associations between dietary intake, caries and levels of caries-associated micro-organisms. Poor oral hygiene, in children consuming unrestricted diets, may influence the salivary levels of mutans streptococci, lactobacilli and yeasts irrespective of the frequency or amount of sugar consumed. Multiple regression analyses revealed that three variables--GI (probably an indicator of toothbrushing behaviour with a fluoride-containing toothpaste), salivary concentration of lactobacilli and frequency of ingestion of confectionery/sugary foods--were independently and positively related to caries experience.

Child↗

PubMed1996

Dental caries and caries-associated micro-organisms in the saliva and plaque of 3- and 4-year-old Afro-Caribbean and Caucasian children in south London.

Three and four-year-old Caucasian and Afro-Caribbean children (n = 641) attending childcare facilities in the London boroughs of Lambeth, Lewisham and Southwark were studied in order to determine the prevalence of caries and caries-associated micro-organisms and the interactions between these for each of the racial groups; dmft (decayed, missing or filled teeth) scores were recorded using British Association for the Study of Community Dentistry criteria. Saliva and plaque samples were taken from each child and the numbers of mutans streptococci, lactobacilli and yeasts per sample were determined. The mean dmft scores of the 3- and 4-year-old Afro-Caribbean children were 0.36 +/- 0.10 and 0.51 +/- 0.13, respectively, compared to 0.80 +/- 0.17 and 1.48 +/- 0.24 for the equivalent Caucasian children (p < 0.001). Mutans streptococci and lactobacilli were recovered less frequently from the Afro-Caribbean children than from the Caucasian, but in both groups there were significant correlations between the plaque and salivary levels of mutants streptococci and caries experience. In both groups, children from whom both mutans streptococci and lactobacilli were isolated had the greatest mean dmft scores and these were not significantly different. Multiple regression analyses demonstrated that, after controlling for age and dmft, there were still significant associations between race and salivary levels of mutans streptococci and lactobacilli, p = 0.0013 and p = 0.0167, respectively. These data indicate that Afro-Caribbean children had lower levels of dental caries than Caucasian children living in the same London boroughs and attending the same preschool care facilities and, after controlling for age and caries experience, they also had lower salivary levels of mutans streptococci and lactobacilli.

Africa↗

PubMed1996

Degradation and utilisation of chondroitin sulphate by Streptococcus intermedius.

Streptococcus intermedius, part of the 'Streptococcus milleri group', has the ability to produce glycosaminoglycan depolymerising enzymes (hyaluronidase and chrondroitin sulphate depolymerase) which is unique amongst the viridans streptococci and may contribute to their virulence in brain and liver abscesses. The growth of S. intermedius strain UNS 35 was studied in basal medium supplemented with chondroitin sulphate A (CS-A, sulphated at position 4 of the N-acetylgalactosamine moiety) or chondroitin sulphate C (CS-C, sulphated at position 6 of the N-acetylgalactosamine moiety) as the major carbohydrate source. CS-A but not CS-C supported the growth of S. intermedius. Extracellular degradation of CS-A resulted in the initial accumulation of 2-acetamido-2-deoxy-3-O-(beta-D-gluco-4-delta-enepyranosyluronic acid)-D-galactose (deltaUA GalNAc-0S), and low levels of 2-acetamido-2-deoxy-3-O-(beta-D-gluco-4-delta-enepyranosyl uronic acid)-4-O-sulpho-D-galactose (deltaUA GalNAc-4S) in the medium with GalNAc-0S being subsequently utilised during bacterial growth. Metabolic end-products included formate and ethanol but not lactate, indicating that growth was probably carbon-limited. The CS-A contained 30% CS-C, which was also depolymerised resulting in the formation of 2-acetamido-2-deoxy-3-O-(beta-D-gluco-4-delta-enepyranosyluronic acid)-6-O-sulpho-D-galactose (deltaUA GalNAc-6S) in the culture supernate, but this unsaturated disaccharide was apparently not utilised during growth. The results indicate that S. intermedius produced CS-AC depolymerase, which was inducible and extracellular, and sulphatase activity. Experiments with authentic deltaUA GalNAc-4S and deltaUA GalNAc-6S demonstrated that deltaUA GalNAc4S rather than deltaUA GalNAc-6S was the preferred substrate for the sulphatase. Therefore, it is suggested that the CS-AC depolymerase of S. intermedius may play a role in the destruction of CS in host tissues, facilitating bacterial spread, and also in bacterial nutrition by the liberation of nutrients at the site of infection.

Carbohydrate Sequence↗

PubMed1996

Purification and properties of a novel glycosaminoglycan depolymerase from Streptococcus intermedius strain UNS 35.

A glycosaminoglycan (GAG) depolymerase that acts on chondroitin sulphate A (CS-A), chondroitin sulphate C (CS-C) and hyaluronic acid (HA) was purified to apparent homogeneity from a culture of Streptococcus intermedius, strain UNS 35, grown in minimal medium supplemented with CS-A as the sole carbon source. The enzyme was purified by ammonium sulphate precipitation followed by serial chromatography on DEAE Trisacryl M, CM Trisacryl M and heparin-agarose. SDS-PAGE analysis of the purified enzyme yielded a single band with a mol.wt of c. 83000. The purified GAG depolymerase was unusual in its substrate specificity. The enzyme was initially regarded as a CS depolymerase because of its induction by CS-A. However, the GAG depolymerase exhibited greatest activity against HA, whereas the degradation rates of CS-A and CS-C were c. 8% and 2%, respectively, of the rate with HA. On this basis the enzyme could be classified as a hyaluronidase rather than a CS depolymerase. The pH optimum was around neutrality and the enzyme was unusual in having a high pI of approximately 9.3.

Chondroitinases and Chondroitin Lyases↗

PubMed1996

Effect of mucin and glucose on proteolytic and glycosidic activities of Streptococcus oralis.

The production of glycosidase and protease activities, which may play a role in the degradation of human glycoproteins, by Streptococcus oralis strains isolated from endocarditis, septicaemia or the oral cavity was investigated with a range of fluorogenic substrates. The pH optima of the proteases ranged from 6.0 to 9.3 and the pH optima for the glycosidases were lower (4.5-6.0), although the pH range over which both groups of enzymes acted was broad. Growth in a minimal medium supplemented with glucose resulted in repression of glycosidase activities and elevated proteolytic activity. Bacteria from cultures supplemented with porcine gastric mucin (PGM), a model glycoprotein, exhibited higher levels of glycosidase activity, while proteolytic activity was suppressed and glycoprotein-derived monosaccharides were transported at significantly higher rates than those observed for cells grown in media with glucose. PGM-derived cells also exhibited high levels of N-acetylneuraminate pyruvate-lyase, the first intracellular enzyme in the pathway of sialic acid catabolism. Taken together, these data indicate that S. oralis strains produce a range of proteolytic and glycosidic enzymes that may play a role in the degradation of host-derived glycoproteins.

Amino Acid Sequence↗

PubMed1996

Metabolism of glycoprotein-derived sialic acid and N-acetylglucosamine by Streptococcus oralis.

Nine strains of Streptococcus oralis, isolated from blood cultures of patients with infective endocarditis or from the oral cavity as part of the normal flora, were examined for their ability to elaborate sialidase (neuraminidase) and N-acetylglucosaminidase, enzymes which are involved in the degradation of glycoproteins. Both glycosidases were induced when bacteria were grown in a minimal medium supplemented with porcine gastric mucin, a model glycoprotein, and repressed when growth occurred in the presence of glucose. Cell-free extracts mucin-grown cultures expressed elevated levels of N-acetylneuraminate pyruvate-lyase (the first intracellular enzyme in the pathway of N-acetylneuraminate catabolism), N-acetylglucosamine (glcNAc)-6-phosphate deacetylase and glucosamine-6-phosphate deaminase (enzymes involved in the intracellular catabolism of GlcNAc 6-phosphate); activity of each of these intracellular enzymes was markedly repressed when bacteria were grown in media supplemented with alpha 1-acid glycoprotein, a major component of human plasma. Cells from these cultures expressed high levels of sialidase, N-acetylglucosaminidase, and the intracellular enzymes involved in the catabolism of N-acetyl-sugars released by action of these glycosidases. High-resolution 1H-NMR spectroscopy of spent culture supernatants revealed that sialic acid and GlcNAc residues of the molecularly mobile oligosaccharide side-chains of alpha 1-acid glycoprotein had been hydrolysed and the released sugars internalized by the bacteria. These data indicate that S. oralis has the ability to hydrolyse constituents of oligosaccharide side-chains of host-derived glycoproteins and to utilize simultaneously these released carbohydrates. The biochemical characteristics induced by the growth of S. oralis on glycoproteins may play a role in the survival and persistence of these bacteria at the infection site in vivo.

Acetylglucosamine↗

PubMed1996

Azithromycin in the treatment of periodontal disease. Effect on microbial flora.

Azithromycin is an azalide antibiotic with excellent in vitro activity against a wide variety of oral bacteria. It has a long half-life, good tissue penetration and is preferentially taken up by phagocytes. We investigated the microbiological efficacy of azithromycin as an adjunct to the non-surgical treatment of adult chronic periodontitis; its clinical efficacy is dealt with in a separate paper. 46 patients were treated in a double-blind placebo controlled trial. Microbiological assessment of the same periodontal pocket (initially > 6 mm) was made at weeks 0, 2, 3, 6, 10 and 22. Either azithromycin 500 mg 1 x daily for 3 days or placebo was given at week 2. Particular attention was paid to the numbers of black pigmented anaerobes and spirochaetes present since these are the most commonly implicated pathogens in periodontal disease. Pigmented anaerobes were significantly reduced at weeks 3 and 6 in patients who received azithromycin compared to placebo and remained lower, although not significantly so, throughout the study. Counts of spirochaetes were significantly reduced throughout the study in patients who received azithromycin compared to placebo. Our microbiological study suggests that azithromycin may be useful as an adjunct in the treatment of periodontal disease.

Adult↗

PubMed1996

Utilization of sialic acid by viridans streptococci.

The importance of viridans streptococci as agents of serious extra-oral diseases, including endocarditis, is now recognized. We have tested the hypothesis that the ability to utilize sialic acid as a nutrient source may play a role in the proliferation of these organisms. The type strains of the 15 presently recognized species of viridans streptococci and two clinical isolates-S. oralis (AR3), isolated from a patient with infective endocarditis, and S. intermedius (UNS35), a brain abscess isolate-were studied for their ability to utilize sialic acid. Only S. oralis, S. sanguis, S. gordonii, S. mitis ("oralis group") S. intermedius, S. anginosus, S. constellatus ("milleri group"), and S. defectivus ("nutritionally variant group") were able to use sialic acid (N-acetylneuraminic acid) efficiently as a sole carbon source. Formate, acetate, and ethanol were produced as the major metabolic end-products of sialic acid metabolism, while corresponding glucose-grown cultures produced lactate as the major metabolic end-product. Utilization of sialic acid was independent of the production of sialidase. Cell-free extracts of sialic acid-grown cultures expressed elevated levels of N-acetylneuraminate pyruvate-lyase (NPL; the first enzyme in the intracellular catabolism of sialic acid) and N-acetylglucosamine-6-phosphate (GlcNAc-6-P) deacetylase and glucosamine-6-phosphate (GlcN-6-P) deaminase (enzymes involved in the intracellular catabolism of N-acetylglucosamine). These activities were repressed by growth in the presence of glucose. The intracellular fate of sialic acid, after cleavage by NPL into N-acetylmannosamine (ManNAc) and pyruvate, is uncertain, but the elevated levels of GlcNAc-6-P deacetylase and GlcN-6-P deaminase in sialic acid-grown cells suggest that phosphorylation and isomerization are possible steps in the metabolism of ManNAc to generate an intermediate common to the pathway of N-acetylglucosamine metabolism. The species of viridans streptococci that have the ability to utilize sialic acid are those most commonly associated with extra-oral diseases, and this ability is likely to play a role in the persistence and survival of these infecting organisms in vivo.

Acetylglucosamine↗

PubMed1996

Prediction of secondary caries around tooth-colored restorations: a clinical and microbiological study.

Caries at the margins of restorations is difficult to diagnose, and the relevance of staining and ditching around tooth-colored fillings is unclear. This clinical study questions the relevance of marginal color change and marginal ditching to the level of infection of the dentin beneath the margins of tooth-colored restorations. Clinically visible sites (197) on the tooth/restoration margin were selected in 113 teeth. The filling margin and the enamel adjacent to each site were noted as stained or stain-free, and sites were graded as intact, having a narrow ditch, or having a wide ditch. Thirty sites with frankly carious lesions were also included. Plaque was sampled at the tooth-restoration margin and the filling removed. The enamel-dentin junction (EDJ) at each sample site was noted as hard or soft when probed, and the dentin was sampled. Samples were vortexed, diluted, and cultured for total anaerobic counts, mutans streptococci, and lactobacilli. There were more bacteria in the plaque over frankly carious cavities, and the dentin was soft and heavily infected. Only 38 out of 167 sites without frankly carious cavities had soft dentin at the EDJ. Both the plaque and dentin in these sites harbored more micro-organisms. However, none of the clinical criteria chosen would reliably predict the presence of this soft dentin. In this study, only a frankly carious lesion at the margin of the filling constituted a reliable diagnosis of secondary caries.

Adult↗

PubMed1995

Operative and microbiological validation of visual, radiographic and electronic diagnosis of occlusal caries in non-cavitated teeth judged to be in need of operative care.

The diagnosis of occlusal caries depends upon the correct identification of demineralised enamel and dentine. However, tissue demineralisation precedes bacterial infection so that dentine may be demineralised but uninfected. The presence of a bacterial infection of dentine may be a more relevant factor to be considered when planning to restore a carious lesion. The aim of this clinical study was to validate three techniques for the diagnosis of occlusal caries as demineralised tissue and as infected demineralised tissue during cavity preparation. The study sample was 82 non-cavitated occlusal lesions, judged by various dentists to be in need of operative care. The diagnostic techniques used by the single operator were vision, bitewing radiography and electronic caries diagnosis. The validating techniques were a caries detector dye to stain demineralised tissue, microbiological sampling to determine the level of infection of the dentine and clinical assessment of the dentine at operation. The caries detector dye showed demineralised dentine in 96% of the referred lesions. This demineralisation was reliably predicted by the electronic readings. However, the dentine samples from many teeth yielded only small numbers of bacteria indicating no, or only a very low level of bacterial infection. Neither vision nor electronic readings reliably predict heavily infected dentine. Radiographic evidence of dentine demineralisation was significantly associated with heavily infected dentine and this dentine was soft and wet at operation.

Adolescent↗

PubMed1995

Use of CHROMagar Candida medium for isolation of yeasts from dental samples.

A new differential medium, CHROMagar Candida, for the isolation of clinically important yeasts was investigated to determine its usefulness in facilitating the study of oral yeasts. The recovery of yeasts on the medium was not significantly different from the recovery on Sabouraud dextrose agar. The identities of 450 green colonies on CHROMagar Candida, presumptively identified as Candida albicans on the basis of the manufacturer's instructions, were confirmed by testing for beta-N-acetylgalactosaminidase. Candida tropicalis also formed distinctive colonies, and other yeasts including Candida (Torulopsis) glabrata, Candida Parapsilosis, Candida Magnoliae, Candida lusitaniae, Candida Famata, Candida kefir, and Saccharomyces cerevisiae were readily distinguished from C. albicans and C. tropicalis isolates. CHROMagar Candida is a very useful medium, and its use will facilitate the study of yeasts associated with dental diseases.

Candida↗

PubMed1995

Analysis of enzymatic activities for differentiation of two species of nutritionally variant streptococci, Streptococcus defectivus and Streptococcus adjacens.

Strains of nutritionally variant streptococci, Streptococcus defectivus (n = 10) and Streptococcus adjacens (n = 20), were studied for the production of glycosidic and proteolytic enzyme activities. S. defectivus strains produced neuraminidase and alpha-fucosidase, while S. adjacens strains produced only neuraminidase. The S. adjacens strains produced a very wide range of proteolytic activities with the ability to hydrolyze the majority of aminopeptidase substrates tested, while S. defectivus strains hydrolyzed only a minority of aminopeptidase substrates. These data provide additional phenotypic characteristics which may be useful in distinguishing between these two species and suggest that they may have different nutritional requirements.

Amino Acid Sequence↗

PubMed1995

Comparison of selected microflora of plaque and underlying carious dentine associated with primary root caries lesions.

The composition of the microflora recovered from superficial dental plaque sampled from 81 primary root caries lesions requiring restoration was compared with the microflora of the underlying, infected carious dentine. The numbers of bacteria in the plaque samples were significantly greater than in the dentine samples, and the frequency of recovery of mutans streptococci, streptococci, lactobacilli, gram-positive pleomorphic rods (primarily Actinomyces spp.), and yeasts was not significantly different between the paired samples. However, the proportion of lactobacilli and gram-positive pleomorphic rods was significantly greater in the dentine, while the proportions of streptococci and yeasts did not differ significantly; the proportions of mutants streptococci were similar in both samples. These data indicate that the microflora overlying primary root caries lesions is significantly different from that associated with the infected root dentine. The method of sampling and culturing the microflora of root caries lesions must, therefore, discriminate between the microflora of the superficial supragingival plaque and the microflora associated with destruction of the infected underlying dentine.

Actinomyces↗

PubMed1995

Specific and charge interactions mediate collagen recognition by oral lactobacilli.

The mechanisms by which oral lactobacilli, one of the three major genera of cariogenic bacteria, attach to tooth surfaces are unknown. We hypothesize that recognition of collagen, the major component of dentin, may be a mechanism which localizes these bacteria to exposed root surfaces as well as to carious lesions which have penetrated the dentin. We found that the majority of oral Lactobacillus spp. strains recognize and bind collagen type I. Binding of 125I-labeled collagen type I to two strains of L. casei rhamnosus has been characterized in some detail. These strains were previously characterized with respect to their attachment to dentin (Switalski and Butcher, 1994). The process of 125I-collagen binding was mediated via specific as well as charge interactions. The putative adhesin-mediated (specific) interaction involved a limited number of bacterial surface components (2 x 10(3)/cell). Under conditions conducive for non-specific interactions (low ionic strength), the binding was higher by an order of magnitude. Collagen binding strains were found to adhere to collagen-coated surfaces, while strains unable to bind collagen adhered to a much lesser extent. Adherence of bacteria to collagen-coated surfaces could be competitively inhibited with collagen. These interactions may target collagen-binding strains of lactobacilli to dentin collagen in the oral cavity and thus play a role in the pathogenesis of root surface and/or coronal caries. Interference with this collagen-mediated attachment of lactobacilli may provide effective means of caries control, particularly in view of the fact that other oral acidogenic microbiota also interact with collagen.

Adhesins, Bacterial↗