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Bacterial Culture Media

Bacterial culture media is essential for the growth of bacteria.

ayusuf75
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Bacterial Culture Media

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  1. Bacteriological Media:Cultivation of Microbes Dr. Md. Abdullah Yusuf Assistant Professor of Microbiology National Institute of Neurosciences & Hospital Dhaka, Bangladesh Email: ayusuf75@yahoo.com

  2. Learning Objectives • Definition of culture/cultivation and media • Types of culture • Types of microbes as per ability of culture • Basic equipment and logistic arrangement for bacterial culture • Indication of culture • Classification, type and use of bacteriological media

  3. Definition • Cultivation • Process of allowing bacteria to multiply in artificial food providing optimum environment • Culture Medium/media • Artificial food for bacteria for in vitro growth

  4. Types of Culture • Inanimate • Using nutritional ingredients but no living cells or tissues • Used for culture of bacteria and fungus • Animate • Using nutritional ingredients and metabolic substrate for living cells or tissues to multiply (Tissue/Cell Culture) • Used for in vitro multiplication of virus, rickettsia, chlamydia

  5. Types of Bacteria as per ability to Culture • Some bacteria can multiply easily • ordinary • some with difficulties • fastidious • some cannot • uncultivable

  6. Conti…. • Fastidious • Neisseria gonorrhoea • Neisseria meningitides • Haemophilus influenzae • Uncultivable • Mycobacterium leprae • Treponema pallidum

  7. Culture technique

  8. Materials Needed for Culture • Specimen • Sterile Cotton Swab • Bacteriological Wire Loop • Suitable Culture Media • Incubator • Aerobic • CO2/Anaerobic

  9. Indication of Culture • Isolation- diagnosis • Identification- diagnosis • Antimicrobial susceptibility- treatment • Genomic study- characterization • Progressive research- up to date information

  10. Culture Media Classification A. On the basis of consistency • Liquid • Solid • Semi-solid (gel)

  11. Conti… B. On the basis of nutritional ingredients • Simple or basal • Enriched • Selective • Indicator • Differential

  12. Classification-contd C. On the basis of use • Primary • Subculture • Transport • preservative

  13. Important points • Liquid media is also called broth • Solid media • Liquid media + solidifying agent in appropriate concentration (5-10%) • Semisolid media • liquid media + solidifying agents at low concentration (study bacterial motility)

  14. Solidifying agents • Agar agar (sea weeds) • melt at high temperature (55-600 C) • solidified at low temperature (40-450 C) • Egg whole • Gelatin • Potatoes • Tomato powder • Serum

  15. According to ingredients • Simple/basal • contain basic nutrient support • Enriched • contain growth enhancing substances. e.g.- blood, serum, haemoglobin • Selective • inhibitory substance that do not inhibit one group/species, but inhibit all other • Semi-selective • if allow growth of one family-many members • Highly selective • allow only one species of a particular genus

  16. According to Ingredients (contd.) • Indicator • contain chemical substance that changes it’s colour with change of pH • indicate particular property of a genus of bacteria • Differential • substance with change of colour (black colour due metalic tellurium) or phenomenon (haemolysis) observed due to growth of a particular bacteria

  17. According to Use • Primary • first inoculation then transfer or not • Subculture • subsequent inoculation from primary media • Transport • Dissolve or mix clinical specimens or bacteria • allow little growth but no inhibition • transported from one location to another • Preservative • dehydrated media containing metabolically inactive bacteria • kept for prolonged period (lyophilized skimmed milk)

  18. Subculture

  19. How a medium can be made selective? • Adding inhibitory substance • bile salt in MacConckey agar • Adding antibiotic • Campybap for Campylobacter • Adding alkali/ Changing pH • Sodium bi carbonate in alkaline peptone water • Removing oxygen • by reducing chemicals or mechanically for anaerobic bacteria • Changing temperature • thermophiles grow at high temperature

  20. Advantages of solid media over liquid media • Discrete growth as separate unit (colony) • hazy or opaque appearance in liquid • Clear colony morphology • Easy to pick-up for subculture • Sensitivity test or further identification tests

  21. Differential media

  22. Haemolysis in blood agar

  23. Blood agar

  24. Thank You

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