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Scientists sharpen view of gene transfer between pathogenic bacteria

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May lead to ways to curtail spread of antibiotic resistance.

Bacteria possess the ability to take up DNA from their environment, a skill that enables them to acquire new genes forantibiotic resistance or to escape the immune response. Scientists have now mapped the core set of genes that are consistently controlled during DNA uptake in strep bacteria, and they hope the finding will allow them to cut off the microbes' ability to survive what doctors and nature can throw at them.

The findings, by a team of researchers from the University of Oslo, the Forsyth Institute, and the University of Illinois at Chicago, appeared last week in the American Society for Microbiology's new open-access journal, mSystems.

The researchers wanted to know precisely which metabolic pathways in the bacterial cell must be activated for the bacteria to become "competent," or able to acquire genes from DNA in the environment. They focused on Streptococcus mutans, a strain involved in tooth decay.

Earlier studies of competence had pointed to more than 300 active genes. The new study identifies only 83 genes in 29 regions of the strep chromosome that are specific to the competence pathway, with 27 of these genes lying within an interconnected network controlled by one of three key regulator molecules. When the researchers compared the new results to earlier studies in five other strep species, they found that in all those species a core set of only 27 activated competence genes was required for DNA uptake.

"Streptococcus is a diverse group of species that evolved from a common ancestor to adapt to diverse hosts and sugar-rich niches," says study co-author Donald Morrison, professor of biological sciences at UIC. "Our findings -- that two-thirds of the core activated genes in streptococcus have transformation functions -- suggest that this is an ancient response, maintained because of its value in promoting ready access to external DNA."

 

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Non-inflammatory destructive periodontal disease

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NIDPD case was studied in order to analyze features of the disease, and discuss the possible etiologic factors.

Although, bacteria are a critical etiologic factor that are needed to develop periodontal disease, bacteria alone are insufficient to induce periodontal disease. A susceptible host is also required, and the host's susceptibility as local and/or general predisposing risk factors, are important determinants of the disease status.

An accurate diagnosis is often essential in developing a predictable and suitable treatment plan, which, when executed, gives a guide to the resolution of the periodontal disease's activity. The majority of all forms of periodontal diseases, are considered as microorganism-induced diseases, which promote an inflammatory host defense response against the bacteria and noxious materials from bacterial plaque.

The inflammatory process inactivates bacteria, but produces the liberation of bacterial and neutrophil derived products such as enzymes, which induce periodontal tissue destruction by lytic activities. Therefore, the characteristics of the most common periodontal disease are: presence of gingival inflammation, ulceration of the junctional epithelium, loss of connective tissue and alveolar bone, causing apical migration of the junctional epithelium and development of periodontal pockets.

However, not all types of periodontal disease seem to be caused by periodontopathogenic bacteria, and not all are distinguished by an evident inflammatory process, and periodontal tissue destruction associated with periodontal periodontal pocket formation and progressive deepening. Non inflammatory destructive periodontal disease (NIDPD), is a severe destructive periodontal disease, which is characterized by periodontal attachment loss, alveolar bone loss, generalized gingival recession without pathognomonic sign of inflammation, and periodontal pocket development. Conventional periodontal therapy and antimicrobial therapy are ineffective, in preventing further progression of the disease. A NIDPD case was studied in order to analyse features of the disease, and discuss the possible etiologic factors as an association of endogenous opportunist bacteria with anatomical aspects, occlusion pattern, emotional stress and mouth breathing condition.

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Researchers analyze potentially hazardous dental drill debris under composite fillings

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While dental drills, or burs, are used extensively in dentistry to mechanically prepare tooth structures for fillings, little is known about the bur debris left behind in the teeth and whether it poses potential health risks to patients.

Imaging analyses have revealed dental bur fragments of different sizes in different locations on the floor of the prepared surface of the teeth and under the filling, which places them in direct contact with the tubules and fluid within dentin. The fragments are made of tungsten carbide-cobalt, which is bio-incompatible.

"Further studies need to investigate if or to what extent the small amount of bio-incompatible debris constitutes a biohazard to patients," said Dr. Assem Hedayat, lead author of the Journal of Synchrotron Radiation article.

 
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