Bacteriological culture media for artificial growth of bacteria

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

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

3. Definition
• Cultivation/Culture
– 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

16. According to ingredients
• Semi-selective
– if allow growth of one family-many members
• Highly selective
– allow only one species of a particular genus

17. 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

18. 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)

19. Subculture

20. 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

21. 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

26. Differential media

27. Haemolysis in blood agar

28. Blood agar

29. Thank You