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P D Marsh

Publications and source records attributed to P D Marsh.

At least 19 recordsLinked to original sources
PubMed2006

Intranasal IFNgamma extends passive IgA antibody protection of mice against Mycobacterium tuberculosis lung infection.

Intranasal inoculation of mice with monoclonal IgA against the alpha-crystallin (acr1) antigen can diminish the tuberculous infection in the lungs. As this effect has been observed only over a short-term, we investigated if it could be extended by inoculation of IFNgamma 3 days before infection, and further co-inoculations with IgA, at 2 h before and 2 and 7 days after aerosol infection with Mycobacterium tuberculosis H37Rv. This treatment reduced the lung infection at 4 weeks more than either IgA or IFNgamma alone (i.e. 17-fold, from 4.2 x 10(7) to 2.5 x 10(6) CFU, P = 0.006), accompanied also by lower granulomatous infiltration of the lungs. IFNgamma added prior to infection of mouse peritoneal macrophages with IgA-opsonized bacilli resulted in a synergistic increase of nitric oxide and TNFalpha production and a 2-3 fold decrease in bacterial counts. Our improved results suggest, that combined treatment with IFNgamma and IgA could be developed towards prophylactic treatment of AIDS patients, or as an adjunct to chemotherapy.

Administration, Intranasal↗
PubMed2006

Comparison of the efficacies of disinfectants to control microbial contamination in dental unit water systems in general dental practices across the European Union.

Water delivered by dental unit water systems (DUWS) in general dental practices can harbor high numbers of bacteria, including opportunistic pathogens. Biofilms on tubing within DUWS provide a reservoir for microorganisms and should be controlled. This study compared disinfection products for their ability to meet the American Dental Association's guideline of <200 CFU x ml(-1) for DUWS water. Alpron, BioBlue, Dentosept, Oxygenal, Sanosil, Sterilex Ultra, and Ster4Spray were tested in DUWS (n = 134) in Denmark, Germany, Greece, Ireland, The Netherlands, Spain, and the United Kingdom. Weekly water samples were tested for total viable counts (TVCs) on yeast extract agar, and, where possible, the effects of products on established biofilm (TVCs) were measured. A 4- to 5-week baseline measurement period was followed by 6 to 8 weeks of disinfection (intermittent or continuous product application). DUWS water TVCs before disinfection ranged from 0 to 5.41 log CFU x ml(-1). Disinfectants achieved reductions in the median water TVC ranging from 0.69 (Ster4Spray) to 3.11 (Dentosept) log CFU x ml(-1), although occasional high values (up to 4.88 log CFU x ml(-1)) occurred with all products. Before treatment, 64% of all baseline samples exceeded American Dental Association guidelines, compared to only 17% following commencement of treatment; where tested, biofilm TVCs were reduced to below detectable levels. The antimicrobial efficacies of products varied (e.g., 91% of water samples from DUWS treated with Dentosept or Oxygenal met American Dental Association guidelines, compared to 60% of those treated with Ster4Spray). Overall, the continuously applied products performed better than those applied intermittently. The most effective products were Dentosept and Oxygenal, although Dentosept gave the most consistent and sustained antimicrobial effect over time.

Biofilms↗
PubMed2005

Dental plaque: biological significance of a biofilm and community life-style.

BACKGROUND: Most microorganisms in nature attach to surfaces and form matrix-embedded biofilms. Biofilms are highly structured and spatially organized, and are often composed of consortia of interacting microorganisms, termed microbial communities, the properties of which are more than the sum of the component species. Microbial gene expression alters markedly in biofilms; organisms communicate by gene transfer and by secretion of diffusible signalling molecules. Cells in biofilms are less susceptible to antimicrobial agents. AIM AND MATERIALS & METHODS: To comprehensively review the literature to determine whether dental plaque displays properties consistent with those of a typical biofilm and microbial community. RESULTS: Novel microscopic and molecular techniques have demonstrated that plaque has a structured architecture with an extracellular matrix, and a diverse composition (around 50% of cells are unculturable). The constituent species communicate by gene transfer, by secreted peptides (gram-positive bacteria) and autoinducer-2 (gram-positive and gram-negative bacteria). These organisms are functionally organized for increased metabolic efficiency, greater resistance to stress and for enhanced virulence. Plaque formation has direct and indirect effects on gene expression. CONCLUSION: Dental plaque displays properties that are typical of biofilms and microbial communities in general, a clinical consequence of which is a reduced susceptibility to antimicrobial agents as well as pathogenic synergism.

Biofilms↗
PubMed2004

Total viable counts, ATP, and endotoxin levels as potential markers of microbial contamination of dental unit water systems.

OBJECTIVES: To determine if either ATP or endotoxin concentrations in water supplied by dental unit water systems (DUWS) correlated with total viable counts (TVC), and therefore could be used as a rapid, chairside measure of levels of microbial contamination. DESIGN: A prospective trial. METHOD: Fifty-seven water samples were taken from the 'triple spray', air rotor and source water supplies from 25 dental units in eight practices. The samples were assayed for endotoxin concentration, total ATP and TVC. A pilot study was performed to assess the relationship between TVC and total cell counts, as determined by flow cytometry. RESULTS: ATP concentrations ranged from 22 to 958 relative light units (RLU) and free endotoxin ranged from 25 to 600 EU ml(-1). TVC varied from not detected to 2.16 x 10(4) CFU ml(-1). The ATP method proved to be a simple and rapid method that could be used at the chairside. However, there was no correlation between ATP or endotoxin concentrations and TVC in DUWS. TVC generally underestimated the total cell count by 50 to 500 fold. CONCLUSION: Half of the water samples from DUWS exceeded recommended levels of TVC. However, ATP and endotoxin concentrations in DUWS water samples did not correlate with these TVC data and therefore could not be recommended as an alternative assay to TVC for measuring bacterial contamination or for monitoring water treatment efficacy.

Adenosine Triphosphate↗
PubMed2004

Intranasal bacille Calmette-Guerin (BCG) vaccine dosage needs balancing between protection and lung pathology.

Intranasal vaccination may offer practical benefits and better protection against respiratory infections, including tuberculosis. In this paper, we investigated the persistence of the Mycobacterium bovis-strain bacille Calmette-Guerin (BCG) Pasteur, lung granuloma formation and protection against pathogenic tuberculous challenge in mice. A pronounced BCG dose-dependent granulomatous infiltration of the lungs was observed following intranasal, but not after subcutaneous, vaccination. Corresponding doses of BCG, over a 100-fold range, imparted similar protection against H37Rv challenge when comparing the intranasal and subcutaneous vaccination routes. Interestingly, a BCG dose-dependent reduction of the H37Rv challenge infection was observed in the lungs, but not in the spleens, following both intranasal and subcutaneous vaccination. In the light of the observed concurrence between the extent of granuloma formation and the level of protection of the lungs, we conclude that intranasal vaccination leading to best protective efficacy needs to be balanced with an acceptable safety margin avoiding undue pathology in the lungs.

Administration, Intranasal↗
PubMed2004

Minimizing prion risk without compromising the microbial composition of biofilms grown in vivo in a human plaque model.

AIMS: To determine whether the stringency of sterilization procedures for biological components of in vivo dental plaque-generating devices based on enamel can be increased to minimize prion risk without compromising natural biofilm composition. METHODS AND RESULTS: The composition of in vitro biofilms, grown on hypochlorite-treated and untreated autoclaved enamel surfaces, was determined using culture-based methods and checkerboard DNA: DNA hybridization analysis. No differences were found between biofilms recovered from either substrate. SIGNIFICANCE: Several in situ models allow generation of plaque in the oral cavity, followed by recovery of intact biofilms for experimentation. Approaches allowing plaque formation on natural tooth surfaces are most valuable, but present a possible infection risk to volunteers wearing plaque-collecting devices, particularly with respect to prions. Hypochlorite treatment of biological material, as an adjunct to autoclaving, reduces infection risk without compromising biofilm composition and should be adopted in all future studies using plaque-generating devices incorporating enamel, where there is a potential prion threat, and further investigated in other biological hard tissues.

Bacteria↗
PubMed2004

Microbiological evaluation of dental unit water systems in general dental practice in Europe.

A range of opportunistic pathogens have been associated with dental unit water systems (DUWS), particularly in the biofilms that can line the tubing. This study therefore aimed to assess the microbiology of DUWS and biofilms in general dental practices across seven European countries, including the United Kingdom (UK), Ireland (IRL), Greece (GR), Spain (ES), Germany (D), Denmark (DK) and the Netherlands (NL). Water supplied by 51% of 237 dental unit water lines exceeded current American Dental Association recommendations of < or = 200 colony-forming units (CFU) ml(-1). Microbiological loading of the source waters was between 0 (Denmark, the Netherlands and Spain) and 4.67 (IRL) log CFU ml(-1); water line samples from the DUWS ranged from 1.52 (ES) to 2.79 (GR) log CFU ml(-1); and biofilm counts ranged from 1.49 (GR) to 3.22 (DK) log CFU.cm(-2). Opportunistic pathogens such as legionellae (DK and ES), including Legionella pneumophila SG1 (DK and GR), and Mycobacterium spp. (DK, NL, GR, D and ES) were recovered occasionally. Presumptive oral streptococci (ES and NL), oral anaerobes (GR), Candida spp. (UK, NL and ES) and blood (GR and IRL) were detected at relatively low frequencies, but their presence indicated a failure of the 3-in-1 antiretraction valve, leading to back siphonage of oral fluids into the water and biofilm phase. These findings confirm that a substantial proportion of DUWS have high levels of microbial contamination, irrespective of country, type of equipment and source water. The study emphasizes the need for effective mechanisms to reduce the microbial burden within DUWS, and highlights the risk of occupational exposure and cross-infection in general dental practice.

Bacteria↗
PubMed2004

The role of Triclosan in dentifrice formulations, with particular reference to a new 0.3% Triclosan calcium carbonate-based system.

AIM: To discuss the role of Triclosan in dentifrice systems and demonstrate the enhanced efficacy of Triclosan in calcium carbonate-based systems when the level of the antimicrobial agent is raised from 0.2% to 0.3%. Triclosan is the most commonly used antimicrobial agent in oral care products, being compatible with a wide range of ingredients found in toothpaste formulations, whilst having no negative sensory features (e.g. taste, staining) that are associated with some other antimicrobial/anti-plaque agents. Triclosan is a broad spectrum antimicrobial agent, with additional anti-metabolic and anti-inflammatory properties. When delivered to the mouth in oral care products, Triclosan can selectively inhibit Gram negative anaerobic bacteria implicated in gingivitis and periodontal diseases, while leaving species associated with oral health relatively unaffected. Worldwide, attempts have been made to boost delivery/activity of Triclosan, either by use of copolymers or by combination with other agents such as zinc citrate. However, Triclosan has also been shown to maintain clinical efficacy against plaque and gingivitis when present as the sole antimicrobial in toothpaste formulations.

Anti-Infective Agents, Local↗
PubMed2003

Plaque as a biofilm: pharmacological principles of drug delivery and action in the sub- and supragingival environment.

Dental plaque is the diverse microbial community, embedded in a matrix of host and bacterial polymers, growing on teeth as a biofilm. Dental plaque develops naturally, and contributes to the host defences by preventing colonization by exogenous species. The composition of dental plaque varies at distinct surfaces as a result of the inherent biological and physical properties at these sites; the balance of the predominant bacterial populations shifts in disease. Plaque has an open architecture, with channels traversing from the biofilm surface through to the enamel. This structure affects the movement of molecules within plaque, and gradients in key determinants develop. Bacteria growing on a surface display a novel phenotype; one consequence of which is an increased resistance to antimicrobial agents. Resistance can result from restricted inhibitor penetration (diffusion-reaction theory), slower bacterial growth rates, transfer of resistance genes, suboptimal environmental conditions for inhibitor activity, and the expression of a resistant phenotype. Such biofilm-associated traits, coupled with the pharmacokinetic profile of orally delivered antimicrobial agents (high concentrations for short periods/lower concentrations for longer periods), affect the mode of action and efficacy of antimicrobials. Agents with a broad spectrum of activity in laboratory studies may display a far narrower inhibitory profile under the conditions prevailing in the mouth. This may result in a selective inhibition of species implicated in disease, or reduced production of virulence factors, while preserving the benefits associated with a resident oral microflora.

Administration, Topical↗
PubMed2003

Are dental diseases examples of ecological catastrophes?

Dental diseases are among the most prevalent and costly diseases affecting industrialized societies, and yet are highly preventable. The microflora of dental plaque biofilms from diseased sites is distinct from that found in health, although the putative pathogens can often be detected in low numbers at normal sites. In dental caries, there is a shift towards community dominance by acidogenic and acid-tolerant Gram-positive bacteria (e.g. mutans streptococci and lactobacilli) at the expense of the acid-sensitive species associated with sound enamel. In contrast, the numbers and proportions of obligately anaerobic bacteria, including Gram-negative proteolytic species, increase in periodontal diseases. Modelling studies using defined consortia of oral bacteria grown in planktonic and biofilm systems have been undertaken to identify environmental factors responsible for driving these deleterious shifts in the plaque microflora. Repeated conditions of low pH (rather than sugar availability per se) selected for mutans streptococci and lactobacilli, while the introduction of novel host proteins and glycoproteins (as occurs during the inflammatory response to plaque), and the concomitant rise in local pH, enriched for Gram-negative anaerobic and asaccharolytic species. These studies emphasized (a). significant properties of dental plaque as both a biofilm and a microbial community, and (b). the dynamic relationship existing between the environment and the composition of the oral microflora. This research resulted in a novel hypothesis (the 'ecological plaque hypothesis') to better describe the relationship between plaque bacteria and the host in health and disease. Implicit in this hypothesis is the concept that disease can be prevented not only by directly inhibiting the putative pathogens, but also by interfering with the environmental factors driving the selection and enrichment of these bacteria. Thus, a more holistic approach can be taken in disease control and management strategies.

Bacteria, Anaerobic↗
PubMed2003

The oral environment: the challenge for antimicrobials in oral care products.

For any antibacterial/ anti-plaque system from an oral care product to be effective, it must firstly be delivered and retained at relevant sites in the oral cavity and secondly, remain active within the chosen formulation to successfully target the biofilm cells within dental plaque. This must include inhibition of the growth and metabolism of relevant organisms associated with disease. This review will concentrate on understanding the environmental conditions in which such oral care products must work and summarise the activity within the oral cavity of the main antibacterial and anti-plaque agents in common oral care products, namely chlorhexidine, essential oils, metal salts and Triclosan. Routes to further enhance the activity of these products, together with the use of relatively novel formats such as confectionery products to provide added consumer oral health benefits will be considered.

Anti-Infective Agents, Local↗
PubMed2003

Microbiological evaluation of a range of disinfectant products to control mixed-species biofilm contamination in a laboratory model of a dental unit water system.

Dental unit water system (DUWS) tubing harbors complex multispecies biofilms that are responsible for high microbial levels at the distal outlet. The aim of this study was to use an established biofilm laboratory model to simulate biofouling of DUWS to evaluate practical, cost-effective, and evidence-based methods of microbial decontamination. Reproducible biofilms were developed in the model over 14 days; decontamination was assessed using total viable counts (TVC) and microscopic-image analysis techniques to view the inner surface of tubing. Flushing did not reduce the biofilm coverage or TVC. Combizyme and ozone did not completely eliminate the viable bacteria (70 and 65% reduction in biofilm TVC, respectively), nor did they remove the biofilm (45 and 57% reduction in biofilm coverage, respectively). Chlorhexidine and Bio2000 (active agent: ethanol and chlorhexidine), Tegodor and Gigasept Rapid (aldehyde based), and Grotanol (hydroxide based) completely eliminated the TVC but did not completely remove biofilm (31, 53 33, 34, and 64.9% reduction of biofilm coverage, respectively). Other products including Grotanol Flussig (phenol based), Betadine (povidone-iodine based), Alpron (chlorite based), and the hydroxide-containing products Sporklenz, Sterilex Ultra, Dialox, Sterilox, Sanosil, Oxigenal, and Grotanat Bohrerbad resulted in a 100% reduction in the biofilm TVC and a >95% reduction in biofilm coverage. The study demonstrated that while many disinfectants achieve a sufficient reduction in TVC they may not necessarily remove unwanted biofilm from the tubing surfaces as tested in this laboratory-controlled biofilm model.

Bacteria↗
PubMed2001

A guinea pig model of low-dose Mycobacterium bovis aerogenic infection.

In order to develop a model of Mycobacterium bovis infection with pathogenetical relevance, a modified version of the Henderson apparatus was used to deliver infectious aerosols directly to the snouts of guinea pigs. Aerosols generated from 10(6), 10(7), 10(8)CFU/ml M. bovis suspensions established disease in every animal, with estimated retained doses of 10, 100, 1000 CFU, respectively. For comparison, other guinea pigs were inoculated with 100 CFU M. bovis intramuscularly (i.m.). Pathology and bacterial colonisation of lungs and spleen varied according to the dose and route of inoculation. Animals inoculated i.m. gave a significant cutaneous tuberculin hypersensitivity reaction earlier after testing than those infected aerogenically. A serological response to M. bovis antigens was detected in all infected animals. Intensity of antigen recognition was dose-dependent and although the range of antigens recognised varied between animals, a 25 kDa antigen present in the cell fraction was serodominant. Thus, a reproducible guinea pig model has been defined that may be suitable for virulence, vaccination, and immunological studies.

Administration, Intranasal↗
PubMed2001

Ultraviolet disinfection with a novel microwave-powered device.

AIMS: To evaluate the antimicrobial efficacy of a novel u.v. beaker, powered in a domestic microwave oven. METHODS AND RESULTS: Three beakers were compared, with most rapid killing obtained in the Neutra Plasma 50. Ultraviolet light generated within the beakers efficiently killed planktonic and surface-associated Streptococcus mutans, Pseudomonas aeruginosa, vegetative Bacillus stearothermophilus, herpes simplex and polio viruses. Candida albicans and Mycobacterium phleii were less rapidly killed, and only 70% inactivation of B. stearothermophilus endospores was achieved. Irradiation for 45 s reduced viable bacterial counts in saliva by > 99%. CONCLUSIONS: The u.v.-generating beakers efficiently reduced viable counts of bacteria, yeast and viruses. Kinetics of killing varied, reflecting the fact that lethal mechanisms are complex, and probably depend on interplay between u.v. and heat. SIGNIFICANCE AND IMPACT OF THE STUDY: This novel method of generating u.v., using a cheap and widely available power source, provides a rapid, inexpensive and non-toxic method of disinfection with a wide range of applications in hospitals, clinics and the home.

Bacteria↗
PubMed2000

Microbial aerosols in general dental practice.

OBJECTIVE: To measure the concentration of microbial aerosols in general dental practices and to use this information to carry out quantitative microbiological risk assessments. METHODOLOGY: Microbial air sampling was carried out continuously during 12 treatment sessions in 6 general dental practices in the South West of England. RESULTS: The microbial aerosol concentration in treatment rooms was generally less than 10(3) colony forming units per cubic metre of air (cfu x m(-3)). However, in 6 out of the 12 visits, at least one peak concentration with much higher numbers of bacteria was detected. The peak concentrations were associated with increased recoveries of presumptive oral streptococci suggesting these aerosols originated from the mouths of patients. These aerosol peaks dissipated within 30 minutes and no dissemination into waiting areas was detected. The peak concentrations were associated with mechanical scaling procedures (47% of procedures giving rise to a peak) and to a lesser extent by cavity preparation (11%). No aerosolised blood was detected. CONCLUSIONS: The data have been used to generate a framework for quantifying risk of exposure of staff to aerosolised microbial pathogens in general dental practice. For example, dentists and their assistants may have a slightly higher risk of exposure to Mycobacterium tuberculosis than the general public. The use of face seal masks that have been shown to protect against aerosolised micro-organisms may reduce this exposure.

Aerosols↗
PubMed2000

Temperature elevation regulates iron protoporphyrin IX and hemoglobin binding by Porphyromonas gingivalis.

Porphyromonas gingivalis, an obligate anerobe with a growth requirement for iron protoporphyrin IX (FePPIX), is exposed to increased temperatures in the inflamed periodontal pocket. In this study, P. gingivalis was grown in a chemostat at 37 degrees C (control), 39 degrees C, and 41 degrees C, and examined for hemagglutinating (HA) activity, hemoglobin binding and degrading activity, and iron protoporphyrin IX binding. HA activity decreased in cells as the growth temperature increased. Binding of mu-oxo bishaem (dimeric haem), and Fe(II)- and Fe(III)-monomeric forms was increased in 39 degrees C-grown cells but decreased in 41 degrees C-grown cells compared with controls. Cellular hemoglobin binding and degradation decreased with increased growth temperature. The decrease in cellular hemagglutination and hemoglobin degradation occurring with increased growth temperature would limit the potential overproduction of toxic monomeric haem molecules. The increased binding of mu-oxo bishaem and monomeric forms of FePPIX at 39 degrees C may reflect a defense strategy against reactive oxidants and a mechanism of dampening down the inflammatory response to maintain an ecological balance.

Hemagglutination Tests↗
PubMed2000

The physiology and pathogenicity of Mycobacterium tuberculosis grown under controlled conditions in a defined medium.

A chemically-defined culture medium was developed which supported batch growth of Mycobacterium tuberculosis, strain H37Rv, at a minimum doubling time of 14.7 h. This medium also facilitated chemostat culture of M. tuberculosis at a constant doubling time of 24 h. Chemostat growth was optimized at a dissolved oxygen tension of 20% (v/v) and 0.2% (v/v) Tween-80. Chemostat cultures were dispersed suspensions of single bacilli (1.5-3 microm long), or small aggregates, at a mean density of log10 8.3 cfu ml-1. A limited number of amino acids was utilized (alanine, asparagine, aspartate and serine were depleted by >50%; glycine, arginine, isoleucine, leucine and phenylalanine, by approximately 40%). Chemostat-grown cells were pathogenic in aerosol-infected guinea pigs, producing disseminated infection similar to that caused by plate-grown cells. Cells from chemostat culture were significantly more invasive for J774A.1 mouse macrophages than agar- or batch-grown cells. This study demonstrates the suitability of chemostat culture for the growth of pathogenic mycobacteria in a defined physiological state with potential applications for the controlled production of mycobacterial components for therapeutic and vaccine applications.

Animals↗