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Microbiology Australia Microbiology Australia
Issue 3

Vertical Transmission, August 2005

Associate Professor Keryn Christiansen, who is the Director of the Department of Microbiology and Infectious Diseases at Royal Perth Hospital, has been elected unopposed as President-elect of ASM. A/Prof Christiansen will take up her position after the Annual General Meeting in Canberra in September. She will then assume the office of President of the ASM from July 2006 for a two year term. A/Prof Christiansen is responsible for the Gram Positive Typing and Research Unit in Western Australia, which has a strong research interest in MRSA includi...

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Microbiology in decay: A field needing filling

?Nothing could be more unfortunate than to divorce dental research in any way from the rest of scientific and, particularly, medical, research. The solution of the problems relating to dental disease demands more fundamental knowledge than is at present available. The organisation of this knowledge calls for investigations in which ?bacteriologists must participate.? This quotation comes from what was commonly called the Treviot Committee?s report of 1946. To put the Treviot report into perspective, it was not until 10 years later that Orland s...

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Do dental diseases resemble ecological catastrophes?

Ecological catastrophes can take many forms, and can come in all shapes and sizes! Nitrogenous fertilisers can be washed off farm-land into lakes and ponds, resulting in overgrowth by algae. Such an overgrowth can lead to secondary effects to the ecosystem; the algae can consume dissolved oxygen in the water leading to the loss of aerobic microbial, plant and insect life (eutrophication). Similarly, atmospheric pollution with sulphur dioxide and nitrogen oxides can produce acid rain causing damage to plants and trees and loss of aquatic life. O...

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Combating dental decay

Dental caries or tooth decay is one of the most prevalent bacterial infectious diseases of mankind. In recent oral health surveys, more than 60% of Australian teenagers surveyed had experienced the disease and most dentate adults surveyed exhibited multiple teeth affected by caries. Treating the consequences of dental caries accounts for over 50% of the total cost of providing dental services in Australia, which in 1998 was estimated at $2.6 billion. Dental caries is a dynamic process that is initiated by microbial biofilms on the tooth surface...

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Caries and periodontal disease: Two diseases, one biofilm

Dental plaque, a natural oral biofilm is involved in the aetiology of dental caries and periodontal disease. Despite decades of research, the microbiology, aetiology and pathogenesis of these diseases remain controversial. A number of factors interplay in these diseases, the indigenous microbes that inhabit the oral cavity, diet, host susceptibility and time. The ?Non-Specific Plaque Hypothesis? (NSPH) was proposed where the overall mass of plaque interacted with the host and caused disease. An alternative view was the ?Specific Plaque Hypothes...

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Virulence factors in streptococcal infective endocarditis

Infective endocarditis (IE) is a life threatening, endovascular infection occurring when bacteria enter the blood stream and adhere to heart valves. Mortality rates remain in the range of 11-27%. The most common infecting micro-organisms are now the staphylococci (44%) although streptococci (31%) and particularly the oral streptococci (21%) are still major causative agents. Many different oral streptococci have been isolated from IE cases, the most common being Streptococcus sanguinis, Streptococcus oralis, Streptococcus gordonii, Streptococcus...

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Molecular taxonomy of polymicrobial diseases ? finding novel bacteria not previously considered to be associated with oral diseases

Recombinant DNA technology and molecular biology have brought a revolution to the limitations imposed by traditional taxonomic methods of bacterial identification based solely on cultivation. Following on from the novel research of Carl Woese, molecular taxonomy is generally based on variations in the sequence of the 16S rRNA gene and has brought a new perspective to our understanding of the diversity of uncultured bacteria in a multitude of microbial habitats. Analysis of the polymicrobial oral diseases is no exception.

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A proteomic approach to understanding the biofilm phenotype

The current theory for dental decay, the ecological plaque hypothesis, states that the onset of disease follows unfavourable disruption of the dynamic balance between the host and the microbial biofilm community at local sites. Inherent in this theory is the concept that cariogenic bacteria, such as Streptococcus mutans, can be present in health, but at levels that are not clinically relevant and that disease can be controlled not only by targeting pathogens but also by interfering with the factors responsible for driving the deleterious shifts...

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Targeting of a key pathogen in a polymicrobial infection

The major oral diseases of caries and periodontitis are polymicrobial infections initiated by complex microbial biofilms that develop adjacent to the affected tissues. Bacterial plaque adherent to the tooth surface extends below the gingival margin and is increasingly dominated by facultative and obligate anaerobes. The dense plaque adherent to the tooth surface is in apparent equilibrium with a less structured fluid matrix that is in turn in some form of equilibrium with the biofilm adjacent to the surface of the epithelium that lines the ging...

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Signal peptide pheromones in oral streptococcal biofilms

Oral streptococci are known to modulate various physiological properties by responding to secreted signal peptide pheromones. These molecules accumulate in the environment and trigger a genetic response in the target cells at a threshold cell density, thereby synchronising a metabolic outcome with population density. In this review, we summarise how signal peptide pheromones of oral streptococci function. The possibility of targeting these peptide pheromones for the prevention of biofilm-associated infections such as dental caries is also discu...

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The immunopathology of periodontal disease: links with atherosclerosis?

Chronic inflammatory periodontal disease occurs as a result of an inflammatory response in the periodontium which is elicited by bacteria present in dental plaque. The specific cytokines and chemokines produced by this initial response cause a T cell/macrophage dominated inflammatory infiltrate to develop in the connective tissues. If this cell-mediated immune response does not control the bacterial challenge, progression to a B cell/plasma cell lesion occurs (reviewed in Gemmell et al. 20021). A component of the specific T cell and antibody re...

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The Great Bacterial Reef: Communication and development in human oral bacterial biofilms

Consider that The Great Barrier Reef is home to thousands of species of plants and animals with spatiotemporally predictable fish communities on coral reefs, and compare this with the fact that human oral bacteria develop spatiotemporally predictable dental plaque communities on enamel after each oral hygiene procedure. This reassembling of oral bacterial communities over a time interval of only a few hours offers an opportunity to investigate the role of communication in community architecture and composition.

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ASM Affairs, August 2005

Emerging Microbiologists; Culture Media SIG; NSW BD Awards Night; ASM South Australian Branch Report; Antimicrobial SIG workshop in Canberra 2005

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