Bacteriological Culture Media

Bacteriological Culture Media

Dr. Mejbah Uddin Ahmed

Several Terms Media: The nutrient material in which bacteria grow. Culture: A bacterial growth in media. Broth: A liquid medium. Agar plate: Round culture dish with semisolid nutrient media.

Several Terms Slant: Tube with semi-solid media, with a slanted surface. Colony: A circular area of limited bacterial growth. Pure colony: A colony thought to contain only the descendants of a single bacterium

Several Terms Fastidious: Bacteria that require very strict nutrients. Facultative: Able to live in various conditions. Obligate: Can only survive under certain circumstances. Aerobe: Bacteria that live on oxygen. Anaerobe: Bacteria that are inhibited by oxygen.

Method of aenerobiasis Exclusion of air: ● Liquid media may be heated to drive off oxygen, cooled then inoculated & covered with vaselin. ● Shake culture ● Stab culture. ■ Addition of reducing substances: Glucose, thioglycolic acid, ascorbic acid.

Method of aenerobiasis Removal of air: ■ Removal of oxygen and replace by nitrogen & hydrogen: McIntosh and Filde,s anaerobic jar. ■ Self contained anaerobic system.

Several Terms Microaerophilic: Bacteria that require low levels of oxygen. Aerotolerant: Bacteria that prefer anaerobic conditions but can survive in minimal oxygen. Colony morphology: Shape, appearance, size, color of a colony.

Types of Media On the basis of constituent: ● Basic Media ● Enriched media ● Selective media ● Indicator media ● Transport media

Types of Media Basic media: These are simple media, such as: nutrient broth media, nutrient agar media. Enrichment media: Media which contains enrichment substances such as: blood, serum, peptone, yeast extract, vitamins etc. e, g; blood agar, Chocolate agar media.

Types of Media Selective media: Media which contains substances like; bile salt, chemicals, dyes, antibiotics which inhibit growth of unwanted organisms: TCBS agar. Indicator media: Media which contains substances to differentiate microorganisms: MacConkey agar.

Types of Media Transport media: These media contains substances to prevent growth of unwanted organisms and used for survival of pathogens when cannot be cultured immediately: Cary-Blair media.

Culture Media • Broth (liquid) in a tube

▪ Agar (solid) in a petridish

Culture Media

Tryptic Soy Broth (TSB)

MacConkey Agar

Types of Media On the basis of consistency: ● Liquid media. ● Semisolid media (0.5% agar). ● Solid media (1-2% agar). ■ Solidifying agents: Gelatine, Agar, Egg, Serum.

Colonies of Various Species

Sterilization of culture media Depends on type and constituents: ● Autoclaving ● Filtration ● Steaming at 100ºC

*** Sterility testing?

*** How to inoculate culture media? Inoculation of media in petri dish: By wire loop. Inoculation of slope: By straight wire. Inoculation of stab culture: By straight wire. Inoculation of fluid media: By straight wire, Pasture pipette.