Lecture 24

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Lecture 24
2010-11-14 23:51:26

Bacterial Biofilms
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  1. Biofilm
    Microbial life on surfaces
  2. Bacteria Can Live in Two Different States
    • Planktonic- dispersed in the liquid
    • Sessile- attached to surfaces covered by liquid
  3. Importance of Surfaces for Microbial Survival and Reproduction
    • 1. Organic and inorganic compounds adsorb to and accumulate on surfaces, so surfaces often contain more nutrients for microbial growth than planktonic surfaces.
    • 2. Microbial cells can attach to surfaces; by attaching, microbes can remain in a habitat favorable for reproduction
    • 3. In biofilms, bacteria are protected from some toxic chemicals
  4. Biofilm Diseases
    • Periodontal disease and dental caries
    • Otitis media (acute ear infection)
    • Bacterial endocarditis (infection of inner surface of the heart and its valves)
    • Cystic fibrosis (chronic disorder resulting in increased susceptibility to serious lung infections)
    • Legionnaire's disease (an acute respiratory infection resulting from the aspiration of clumps of Legionnella biofilms detached from air and water heating/cooling and distribution systems)
    • Nosocomial (hospital-acquired) infections- catheters, medical implants, wound dressings, tracheal inserts
  5. Steps in Biofilm Formation
    • 1. Formation of organic film by adsorption of organic materials like proteins, carbohydrates
    • 2. Attachment of bacteria from planktonic state, trasitioning from planktonic to sessile life style
    • 3. Growth and division of bacteria
    • 4. Exopolymer production and biofilm formation
    • 5. Detachment and dispersal- release of motile cells, detachment of clumps, or migration under shear
  6. Extracellular Polymeric Substance
    Forms a matrix, usually composed of polysaccharide, but can also contain protein and nucleic acids
  7. Pseudomonas aeruginosa
    • Two stages of illness
    • 1. Intermittent respiratory infections, like bronchitis, involving Staphylococcus aureuss, Haemophilus infulenzae, P. aeruginosa
    • 2. Development of a permanent chronic infection with P. aeruginosa