Bacterial Cultivation by hassan1990

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									Lab 13-
Bacterial cultivation
Selective /differential
media
Lab activities:
 Demo selective and differentiation plates
 Streaking bacteria on differentiation plates
Cultivation

   The process of growing microorganisms in
    culture by taking bacteria from the
    infection site (in vivo or environment) and
    grow them in artificial environment in the
    laboratory (in vitro).
Growth needs

   Fastidious bacteria – relatively complex
    growth needs
   Non-fastidious bacteria- relatively basic
    and straightforward growth needs
Phases of growth media

   Broth- Growth of bacteria will change the
    liquid from clear to turbid (cloudy).
   Solid – Agar plates, slants – Bacterial cells
    inoculated on solid media will multiply
    enough to be seen by naked eye.
Colony- (clone)
   Colony- A bacterial population derived from one
    bacterial cell. The cells within the colony have
    identical, genus, species, genetic and
    phenotypic characteristics.
   Pure bacteria - derived from a single colony.
   Selection of a pure colony -most important for
    bacterial identification
Media classification and function

   Enrichment – Used to enhance growth of a
    particular pathogen
   Supportive - support growth of most non
    fastidious bacteria
Media classification and function

   Selective - Contain inhibitory agents that are
    inhibitory to all organisms except those sought
   Differential - Contain factors that allow bacterial
    species to manifest certain metabolic
    characteristics that distinguish them from other
    species.
   Media can be both selective and differential
    based on the ingredients of the medium.
Blood agar plate (BA)
   Nutrient agar with 5% sheep blood
   Cultivation of fastidious and non fastidious bacteria.
   Differential – Identify hemolysis - Some bacteria secrete
    enzymes that lyse red blood cells (hemolysins) such that
    a clearing around the colony appears.
    b   hemolysis- complete clearing (white hemolysis)
    a   hemolysis – incomplete clearing (green hemolysis)
    g   hemolysis- no hemolysis
Mannitol Salt Agar (MSA)
   Both selective and differential medium.
   High salt concentration - inhibits most bacteria.
   Selective for Staphylococcus sp.
   Differentiate between Staphylococcus sp. by the sugar
    mannitol fermentation .
   Mannitol fermention produce acids that change the
    medium pH.
   Peach color- neutral- no fermentation
   Bright yellow- Acidic – mannitol fermentation (Staph.
    coag. pos.- Staph. aureus)
MacConkey Agar (MAC)
   Selective and differential medium.
   Selective - Gram positive bacteria are inhibited by the
    presence of bile salts and crystal violet inhibitors in the
    medium Most of gram negative bacteria will grow.
   Differentiate- Between Gram negative bacteria by their
    ability to ferment lactose.
   Pink colonies- Bacteria that ferment lactose
    (precipitation of some salts in media by acid production).
   Pale colonies- Non fermenters
Eosine Methylene blue (EMB),

   Differentiatial
    between lactose
    fermenting and non
    fermenting enteric
    bacteria
Tellurite Glycine Agar (TGA)
   Selective- Tellurite
    glycine and lithium inhibit
    most bacteria
   Preferential growth of
    Staphyloccoci coagulase
    positive (Staphyloccocus
    aureus)
Bacteria streaked in lab
   Staphylococcus aureus
   Staphylococcus epidermidis   S.aureus     S.epidermidis
   Salmonella pullorum,
   E.coli
                                 S.pullurum    E.coli




                                     EMB and TGA

								
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