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Background

Description of S. Aureus

Staphylococcus aureus, also known as golden staph, is the most common cause of staphylococ infections. It is a gram positive bacterium, that can normally be treated with penicillin, but unfortunately they have become resistant (see MRSA). ([http://www.denstoredanske.dk/Krop,_psyke_og_sundhed/Sundhedsvidenskab/Farmakologi/penicillin]) The nose is regarded as the major site of S. aureus carriage from where the organisms can spread to other parts of the body. About 20% of the population are long-term carriers of S. aureus. Frequently part of the skin flora and the mucosa is transiently contaminated. ([http://cmr.asm.org/cgi/reprint/10/3/505?view=long&pmid=9227864 2]) Transmission of S.aureus to surgical wound via skin carriage in patients who are nasal carriers could be an explanation for endogenous infection. In nasal carriers, the skin is often colonized by S. aureus. Preoperative disinfection may not be effective in the deeper layers of the skin, and S. aureus may thus become a source of infection during surgery ([http://cmr.asm.org/cgi/reprint/10/3/505?view=long&pmid=9227864 2]).

File:Http://www.cassiopeaonline.it/immagini/staphylococcus bacterium.jpg Media:Dennis Kunkel, Microscopy Inc. The ability to control staphylococcal infections in the future will depend on many factors, e.g., development of new therapeutic agents, optimization of infection control measures, and introduction of new medical devices with a reduced risk of infection ([http://cmr.asm.org/cgi/reprint/10/3/505?view=long&pmid=9227864 2]).

Pathogenesis

Staphylococcus aureus is a virulent pathogen that is currently the most common cause of infections in hospitalized patients. The success of S. aureus as a pathogen, and its ability to cause such a wide range of infections, are the result of its extensive virulence factors, ex toxins. ([http://www.journals.uchicago.edu/doi/abs/10.1086/520289 3]), ([JBC Papers in Press. Published on October 16, 2000 as Manuscript M005446200 4]) S. Aureus is normally considered potential pathogen, as it can cause infections but also is seen as a non-pathogen part of the normal flora.

S.aureus infections is plentiful and diverse. The most common infection is of the skin as impertigo, cellulitis or less frequent scalded skin syndrome ([http://www.medicinenet.com/staph_infection/article.htm 4]). If the bacteria enters the bloodstream known as sepsis, the bacteria can spread to organs and many different serious infections can result. Moreover S.aureus infections include pneumonia, endocarditis, osteomyelitis, food poisoning and more ([http://www.medicinenet.com/staph_infection/article.htm 4]).

MRSA

sår billeder

Biofilm

Biofilm: A layer af microbes embedded in an extracellular slime/ adhesive, usually polysaccharide material excreted by the cells and attached to a surface .

A natural corollary of the bacterial ability to communicate with each other and to sense their own numbers is their ability to aggregate into multicellular formations. Such formations offer protection and other advantages in the natural environment. Bacterial cells associated whith wach other in natural enviroments is called a biofilm. Biofilms trap nutrients for growth and microbial population and help prevent detachment af the cell from surfaces. Cell to cell communications is critical in development and maintenance of a biofilm Attatchment of a cell to surface is a signal for the expression of biofilm specific genes. These genes encode proteins that synthesize cell to cell signaling molecules and begin polysaccharide formation. At least four reasons undelie the formation af biofils. 1.) Biofil are a type of defence. 2.) Biofilm formation allow cells to remain in a favorable niche. 3.) Biofilms form because they allow bacterial cells to live in close association with each other. 4.) Biofilm may be the typical way bacterial cells grow in nature.

Media:Michael T. Madigan, John M. Martinko. BROCK BIOLOGY OF MICROORGANISMS, Eleventh edition. 2006. Pearson Prentice Hall. USA. [[Media:Schaechter Moselio, Ingraham. John L. Neidharddt. Frederick C. MICROBE. ASM Preaa. American Society for Microbiology 1752 N St.NW Washington, DC 20036-2904. 2006, USA ]]

Biofilm formation

Hospital Infections

Quorum-sensing

([Quorum Sensing: Cell-to-Cell Communication in Bacteria Christopher M.Waters and Bonnie L. Bassler Department of Molecular Biology, Princeton University, Princeton, New Jersey 5])

Quorum-sensing bacteria produce molecules, termed autoinducers, that functions as chemical signal molecules. The concentration of these signal increase as a function of the number of cells in a colony. Using this chemical signaling, the bacteria can adabt to the current situation, and as a multicellular organism synchronize their behavior. The colony of bacteria forms biofilms, that are sessile microbial communities embedded in a self-produced extracellular polymeric matrix, with the advantages described above. [[Media:Quorum Sensing in Staphylococcus aureus Biofilms Jeremy M. Yarwood,1 Douglas J. Bartels,2 Esther M. Volper,1 and E. Peter Greenberg1* Department of Microbiology, Roy and Lucille Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242,1 and Vertex Pharmaceuticals, Coralville, Iowa 522402 Received 21 October 2003/Accepted 1 December 2003 6]] (5) The strategy is that bacteria at a low level will express protein factors that promote attachment and colonization, whereas they at lager scale will repress these genes and insted express genes of toxins and proteases, that is factors that are required for dissemination. (5)

In s.aureus the genes involved in quorum sensing is known as the Agr-sensing (accessory gene regulator) system.

Team:SDU-Denmark/Background

From 2009.igem.org