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Biomedical subjects

C W Douglas

Publications and source records attributed to C W Douglas.

At least 37 records · Page 2Linked to original sources
PubMed1994

Comparison of amylase-binding proteins in oral streptococci.

Certain species of oral streptococci bind salivary amylase to their cell surface. The patterns of amylase-binding proteins produced by a range of streptococci have been compared by ligand blotting and several characteristics of the binding proteins investigated. Streptococcus gordonii was the most homogeneous species and almost all strains produced proteins migrating with molecular mass 82 kDa and 20 kDa. Other species were more heterogeneous, releasing proteins that resolved at 87 or 82 kDa and/or between 20 and 36 kDa. Binding of amylase to the 82/87-kDa proteins on ligand blots was prevented by amylase inhibitors, amylase substrates and periodate treatment but these had limited or no effect on amylase binding to 20-36 kDa proteins. Also, the 20 kDa protein of S. gordonii Challis was released into culture medium before the 82-kDa protein. These data suggest that there is significant variation in amylase-binding proteins among streptococci and that the high and low molecular mass proteins differ in the way they interact with salivary amylase.

Amylases↗
PubMed1994

Bacterial-protein interactions in the oral cavity.

Bacteria in the oral cavity must interact with salivary proteins if they are to survive. Such interactions can take several forms, either providing nutrients, a means of adhesion to surfaces, or resulting in aggregation or killing and, therefore, clearance of organisms. Recent work has provided an insight into the mechanisms of some of these bacterial-protein interactions, revealing complexity and diversity. For example, the interaction between a putative Streptococcus mutans adhesin, P1 (B, I/II, etc.), and a parotid glycoprotein results in adhesion when it occurs at a surface or aggregation when in solution, and different domains of P1 appear to be involved in the two processes. An alternative strategy is employed by Actinomyces viscosus, which interacts, via its type-1 fimbriae, with a proline-rich salivary protein; however, this interaction occurs only when the PRP is adsorbed to a surface. A. viscosus takes advantage of a conformational change in the PRP when it becomes surface-bound, which exposes a cryptic part of the molecule. A third, and intriguing, type of interaction is seen between various streptococci and salivary amylase. This does not result in either adherence or aggregation but provides organisms with the ability to utilize starch breakdown products for metabolism. An understanding of the mechanisms involved in bacterial-protein interactions could conceivably lead to novel methods for controlling specific pathogens, but the systems operating in the mouth are numerous, complex, and diverse.

Actinomyces↗
PubMed1994

Ethanol and pH levels of proprietary mouthrinses.

This study measured the pH and alcohol (ethanol) content of a number of proprietary mouthrinses available for purchase by the general public, as well as assessing the influence of the alcohol content on police exhaled air analysis (breathalysing) procedures. The majority of the mouthrinses were acidic, some with a pH as low as 3.40. Only one was found to be alkaline and one near neutral in pH. The ethanol content varied from 0 to 27 per cent. The effect of the alcohol content on the results of the exhaled air analysis were transient and would be unlikely to influence any legal proceedings.

Adult↗
PubMed1993

Control of bacteria in dental water supplies.

A simple device which releases chlorhexidine acetate into dental unit water supplies is described. The device comprised methyl methacrylate resin containing 40% by weight of chlorhexidine powder, cast into a rod shape and placed in a reservoir. After initial cleaning by flushing with hypochlorite, five dental units were fitted with the device and five units acted as controls. The device successfully kept four units virtually free of bacteria over a 3-month period but effective cleaning of the tubing within the units was found to be essential for success. Sustained release of chlorhexidine offers one means of tackling the problem of contaminated water in dental units, without resorting to complex pumping or metering systems.

Chlorhexidine↗
PubMed1993

Susceptibility of alpha-haemolytic streptococci causing endocarditis to benzylpenicillin and ten cephalosporins.

A clinical case of streptococcal endocarditis in which the isolate proved susceptible to third- but not first-generation cephalosporins prompted us to examine the susceptibility of 44 alpha-haemolytic streptococci from cases of endocarditis to ten cephalosporins and benzylpenicillin. Twenty per cent of strains were resistant to penicillin, and 20% were tolerant. Cefazolin, cefuroxime and cefpirome were the most active first-, second- and third-generation cephalosporins tested. Other first-generation cephalosporins tested compared poorly to cefazolin. Cefotaxime and cefpirome were moderately active against some penicillin-resistant strains. Penicillin tolerance was common in Streptococcus gordonii, but a correlation between tolerance and dextran production could not be confirmed.

Cephalosporins↗
PubMed1993

Identity of viridans streptococci isolated from cases of infective endocarditis.

The oral streptococci have undergone considerable taxonomic revision in recent years but there is still little information concerning associations between the newly defined species and disease. This study examined the identities of 47 strains of oral streptococci collected from 42 confirmed cases of infective endocarditis. By means of recently described physiological schemes, the most common species identified were Streptococcus sanguis sensu stricto (31.9%), S. oralis (29.8%) and S. gordonii (12.7%). Other related species including S. mitis and "S. parasanguis" were less common. This indicates that attention should be focused on S. sanguis sensu stricto and S. oralis when considering possible pathogenic mechanisms involved in viridans streptococcal endocarditis.

Endocarditis, Bacterial↗
PubMed1993

Mechanisms of platelet aggregation by Streptococcus sanguis, a causative organism in infective endocarditis.

The ability of certain strains of Streptococcus sanguis to aggregate human platelets in vitro may be related to their virulence in the pathogenesis of infective endocarditis. We have studied the mechanisms of aggregation of human platelets by S. sanguis strain NCTC 7863. Platelet aggregation follows incubation of S. sanguis cells with platelet-rich plasma from normal, healthy adults, after a lag of 7-19 min. Platelet aggregation was accompanied by 5-hydroxytryptamine release and thromboxane B2 production. Aggregation was prevented by aspirin and by EDTA. Platelets from two patients with Glanzmann's thrombasthenia did not respond to bacteria. Fixed, washed platelets resuspended in normal plasma were not agglutinated by S. sanguis. Blocking the glycoprotein Ib receptor with a monoclonal antibody inhibited aggregation of PRP. However, S. sanguis did not induce von Willebrand factor (vWF) binding to platelets; nor did the bacteria prevent ristocetin-induced platelet agglutination or vWF binding. The aggregation response was not related to plasma vWF activity levels in normal subjects or in patients with von Willebrand's disease. The platelet response to S. sanguis therefore resembles true aggregation, requiring the cyclo-oxygenase pathway and the presence of glycoprotein IIb/IIIa. The mechanism also involves glycoprotein Ib, but not apparently through irreversible binding of vWF.

Agglutination↗
PubMed1992

The essential features of microorganisms and the rationale for antimicrobial therapy.

Antimicrobial agents have had a major impact on the control of most bacterial diseases; however, viral, fungal, protozoal and helminthic diseases have generally been less amenable to drug therapy. The reason for this lies in the different structural and physiological features that each group of microorganisms have. This article will outline the basic features of the various types of microorganisms, and relate these to the mode of action of commonly used antimicrobial agents.

Animals↗
PubMed1992

Enzymic activity of salivary amylase when bound to the surface of oral streptococci.

The enzymatic activity of salivary amylase bound to the surface of several species of oral streptococci was determined by the production of acid from starch and by the degradation of maltotetraose to glucose in a coupled, spectrophotometric assay. Most strains able to bind amylase exhibited functional enzyme on their surface and produced acid from the products of amylolytic degradation. These strains were unable to utilise starch in the absence of salivary amylase. Two strains failed to produce acid from starch, despite the presence of functional salivary amylase, because they could not utilise maltose. Strains that could not bind salivary amylase failed to produce acid from starch. In no case was all the bound salivary amylase active, and two strains of Streptococcus mitis which bound amylase did not exhibit any enzyme activity on their cell surface. The ability to bind amylase may confer a survival advantage on oral bacteria which inhabit hosts that consume diets containing starch.

Acids↗
PubMed1991

Evaluation of a hygiene monitor for detection of contamination in dental surgeries.

Routines for disinfecting working surfaces in dental surgeries are difficult to monitor without time-consuming and labour-intensive microbiological techniques, yet effective monitoring is a vital part of cross-infection control. Easy to use, on-site methods would be valuable in this context. This study evaluates a portable monitor, the Biotrace Hygiene Monitor, which uses bioluminescence to measure adenosine triphosphate (ATP) on surfaces. Under laboratory conditions, the ability of the monitor to detect whole saliva and Streptococcus sanguis was determined and, in the general practice environment, the level of ATP on surfaces in five dental surgeries was assessed. The minimum amount of saliva detectable was 0.5 microliters and in surgeries, the monitor readily identified numerous surfaces with fairly high levels of ATP. Routine cleaning methods sometimes left ATP on surfaces at levels which represented a cross-infection risk, if it is assumed that the ATP derived from patients' saliva. Modification of cleaning methods resulted in a reduction of ATP levels to within that which could be considered reasonably practicably safe. It is concluded that the Biotrace Hygiene Monitor offers a simple and valuable means of monitoring dental practice cleaning routines.

Adenosine Triphosphate↗
PubMed1991

Actinomycosis associated with a root-treated tooth: report of a case.

An unusual case of a persistent infection related to a root-filled tooth is reported. Microscopical evaluation revealed the cause to be a large mass of Actinomyces-like filaments, and microbiological culture yielded a low level of Actinomyces israelii. The significance of such a presentation is discussed.

Actinomycosis↗
PubMed1991

Evaluation of a dental unit with a built-in decontamination system.

The efficacy of a dental unit equipped with a system that disinfects and sterilizes the water tubing by flushing with glutaraldehyde was evaluated by inserting Bacillus megaterium spores and Pseudomonas and Moraxella species into the water tubing. Up to 10(8) Pseudomonas and Moraxella organisms were killed during the disinfection cycle, but Bacillus megaterium spores were not. Up to 10(5) spores were eradicated by the sterilization cycle, although the system did not consistently kill 10(8) spores. The water tubing of the new unit was not naturally colonized by water bacteria during an 8-month period prior to the study. Evidence suggested that this was due to antimicrobial activity associated with the plastic tubing; therefore, microbial contamination of new dental units, irrespective of their design, would not be expected, until the inhibitory factor in the plastic tubing has leached out.

Bacillus megaterium↗
PubMed1990

Streptococcus parasanguis sp. nov., an atypical viridans Streptococcus from human clinical specimens.

Molecular taxonomic studies were performed on ten strains of an unusual 'viridans streptococcus' that were originally isolated from human throats, blood and urine. On the basis of DNA-DNA hybridization studies the strains formed a single homology group distinct from all recognized species of oral and viridans streptococci. 16S ribosomal RNA reverse transcriptase sequence studies confirmed the genealogical distinctiveness of the human strains. The results of the present study clearly demonstrate that the human strains represent a new species of the viridans group for which the name Streptococcus parasanguis sp. nov. is proposed. The type strain is ATCC 15912.

Base Sequence↗