MBIO 4404 EXAM 2

MBIO 4404 EXAM 2 - MBIO 4404: PATHOGENIC MICROBIOLOGY EXAM...

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MBIO 4404: PATHOGENIC MICROBIOLOGY EXAM #2 REVIEW BIOFILMS: Biofilm = community of microorganisms; a thin layer of cells of a microorganism such as a bacterium or fungus, held to a surface by the material the microorganisms produce. o Composed of: Microbial cells EPS = slime coating comprised of sugars 2 Types of Cells: o 1. Planktonic cells Single-cells that may float or swim in a liquid medium Motility – Phenotype – More susceptible to antimicrobial chemicals designed to kill them than are biofilm bacteria o 2. Biofilm (sessile) cells Microbial cells Great numbers of cells than planktonic Motility – Phenotype – Many of the infections plaguing humans are actually caused by bacteria in the biofilm mode of growth, not the planktonic mode of growth 5 Step Formation Process: o 1. Adhesion (reversible) Adhere to the surface Van der Waals Hydrophobicity Electrostatic Forces o 2. Adhesion of cells (irreversible) Adhesive substances OMPs; LPS; Fimbriae; Pili; Flagella Forces involved Dipole dipole Hydrogen Ionic Covalent Hydrophobic o 3. Microcolony Formation
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Production of EPS (exopolysaharide) Cells grow and divide Layering covering surfaces o 4. Biofilm Structure Formation Formation of EPS Polysaccharides Proteins 98 99% water Anchors cells Protects against environmental stress o 5. Sloughing off of cells Planktonic cells Advantages of Living in a Biofilm: o Protection o Nutrients o Resistance o Community Importance of Biofilms: o Biofilms have been implicated in chronic infections Increased resistance to antibiotics Resistance to innate and immune defense mechanisms Biofilms allow the pathogen to persist in the host Criteria for Biofilm Infection: o 1. Pathogens adhere to a surface o 2. Direct examination reveals clumps of bacteria encased in an EPS matrix o 3. The infection is generally confined to a particular location. Although dissemination may occur, it is a secondary phenomenon. o 4. The infection is difficult or impossible to eradicate with antibiotics despite the fact that the responsible organisms are susceptible to killing in the planktonic state. Methods for Biofilm Treatment: o Physical removal Debridement Surgery o Autoinducer analogs Furanone RIP o Bacteriophage o Enzymes: Dispersin B Advances in Biofilm Treatment: o New criteria for antibiotic susceptibilities Minimum inhibitory concentration (MIC)
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Minimum biofilm eradication concentration (MBEC) o Great need for biofilm treatments New device surfaces New antibiotic carriers
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This note was uploaded on 04/29/2010 for the course MBIO 4404 taught by Professor Moss during the Fall '10 term at Texas Tech.

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MBIO 4404 EXAM 2 - MBIO 4404: PATHOGENIC MICROBIOLOGY EXAM...

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