Culture Media use in microbiology

1. Culture Media use
in microbiology
By:Assist.Prof.Chaital Kalamkar.S
Arihant COP, Ahmadnagar

2. Content....
• Definition
• Silent features
• History
• Classification

3. Microbiological Culture
• Microbiological culture
A microbiological culture, or microbial culture, is a method
multiplying microbial organisms by letting them reproduce in
predetermined culture medium under controlled laboratory
conditions.
• Culture media
The base where microorganisms can grow with the help of
nutrients and under the influence of physical growth
parameters.
All microorganisms cannot grow in a single culture medium .
• Obligate parasite
Some organisms cannot grow in artificial culture medium are
known as obligate parasites.
Examples: Mycobacterium leprae, Rickettsias, Chlamydias,
Treponema pallidum

4. Silent feature of Bacterial culture...
• Bacteria have to be grown (cultured) for them to be subsequent
clinical diagnosis.
• Culturing bacteria is also the initial step in studying its
morphology and it’s identification.
• By appropriate procedure they have to be grown separately
(isolated)on culture media and obtained as pure for study.
• Bacteria have to be cultured in order to obtain antigens from
developing serological assay for vaccines.
• Certain genetic studies and manipulation of the cells also
need that bacteria be cultured in vitro.
• Culturing on solid media is another convention way of
separating bacteria in mixture.

5. History
• Louis Pasteur used simple broths made up of urine or meat extract.
• Robert Koch realized the importance of solid Media and used potato
pieces to grow Bacteria
• It was on the suggestion of Fannie Eilshemius,wife of Walther
Hesse(who was an assistant to Robert Koch) that agar was used to
solidify culture media.
• Before the use of agar , attempt were made to use gelatin as solidify
agent.
• Gelatin had some inherent problem.
• It existed as liquid at normal incubating temperature (35-37°C)
• Digested by certain Bacteria

6. Classification

7. A.Culture media based on consistency
• Solid media:
Solid media contains agar (1.5-2.0%) as solidifying agent and suitable for isolation
of bacteria and determination of colony characteristics.
Examples: Nutrient agar, BAP etc.
• Semi-solid media
Semi-solid media also contains agar but the percentage content is less (0.5%). This
media is useful for determination of motility of bacteria and cultivation of
microaerophilic bacteria.

8. A.Culture media based on consistency
• Liquid media
This media is useful for
determination of motility of bacteria
and cultivation of microaerophilic
bacteria.
Liquid media that do not contains
agar except for required amount of
nutrients.
This media is useful for propagation
of large number of organisms,
fermentation studies and various
tests (Sugar fermentation test).

9. B. Culture media based on composition
• Synthetic medium:
• Chemically defined
• Contain Pure organic and inorganic
compounds
• Exact formula (little variation)
• Example: Peptone water(1%of Peptone
and 0.5% Nacl in water)
• Non synthetic
• Complex Media
• Containn at least one ingredients that is
not chemically defined(extract from plant
and animal)
• No exact formula/tend to be general and
grow wide variety of organisms.
• Example: Blood agar,yeast extract
broth,milk agar

10. C.Culture media based on applications
1. General purpose media/Basic media:
Basal media are simple media that supports
most non-fastidious bacteria and are used for
the isolation of primary microorganisms.
Examples:Peptone water, nutrient broth and
nutrient agar are considered as basal medium.
2. Enriched medium:
Addition of extra nutrients in the basal
medium in form of blood, serum, egg yolk etc.
to make the medium enriched.
They are used to grow nutritionally exacting
bacteria.
Examples: Blood agar, chocolate agar etc.

11. C.Culture media based on applications
3.Selective media:
• They are designed to inhibit unwanted
contaminating bacteria and help to recover
pathogen from a mixture of bacteria.
• Selective media are agar based and
enrichment media are liquid in consistency.
• Addition of antibiotics, dyes, chemicals,
alteration of pH etc. and makes a medium
selective.

12. C.Culture media based on applications
3.Selective media
• They are of various types like:
1. Thayer Martin Agar: It is used to
recover Neisseria gonorrhoeae contains
antibiotics; vancomycin, colistin and
nystatin.
2. Mannitol salt agar and salt milk agar:
They are used to recover S. aureus; contains
10% NaCl.
3. Potassium tellurite: This medium is
used to recover C. diphtheriae; contains
0.04% potassium tellurite.
4. Mac Conkey’s Agar: It is used for
Enterobacteriaceae members contains bile
salt that inhibits commonly gram positive
bacteria.

13. C.Culture media based on applications
3.Selective media
5. Pseudosel Agar or Cetrimide
Agar: It is used to recover
Pseudomonas aeruginosa
contains cetrimide (antiseptic
agent).
6. Crystal Violet Blood Agar: It
is used to recover Streptococcus
pyogenes contains 0.0002%
crystal violet.

14. C.Culture media based on applications
3.Selective and enrichment
media
7. Lowenstein Jensen: This
medium is used to recover
M. tuberculosis is made selective
by incorporating malachite green.
8. Wilson and Blair’s Agar: It is
used for recovering Salmonella
typhi is rendered selective by the
addition of dye brilliant green.

15. C.Culture media based on applications
4.Enrichment Culture Medium:
• Enrichment medium, is liquid
media, used to increase the
relative concentration of certain
microorganisms in the culture prior
to plating on solid selective
medium. It is mainly used as broth
medium.
• Example: Selenite F broth,
tetrathionate broth, alkaline peptone
water are used to recover pathogens
from fecal specimens.

16. C.Culture media based on applications
5.Differential/Indicator Medium:
• In this medium dyes, metabolic
substrates etc. are added so that
the bacteria that utilize them
appear as differently colored
colonies. Such media are called
differential media or indicator
media.
• Differential media allow the
growth of more than one
microorganism but with
morphologically
distinguishable colonies.

17. C.Culture media based on applications
5.Differential/Indicator
Medium:
• Examples:
1. Mannitol Salt agar(mannitol
fermentation = Gram positive bacteria
Staphylococcus aureus produces
yellow colonies with yellow zones.
2. Blood agar (various kinds of
hemolysis i.e. α, β and γ hemolysis).
3. Mac Conkey Agar (lactose
fermenters, pink colonies whereas
non-lactose fermenter produces pale or
colourless colonies.
4. TCBS (Vibrio cholerae produces
yellow colonies due to fermentation of
sucrose).

18. C.Culture media based on applications
6.Transport media:
• These media are used when specimen cannot be
cultured soon after collection. This media
prevent drying (desiccation) of specimen,
maintain the pathogen to commensal ratio and
inhibit overgrowth of unwanted bacteria.
• Example: Cary Blair medium, Amie’s medium,
stuart’s medium etc. Stuart’s and Amie’s media are
semi-solid media in consistency.
• Addition of charcoal serves to neutralize inhibitory
factors. Cary Blair transport medium is used to
transport feces from suspected cholera patients.
• Pike’s medium is used to transport streptococcii
from throat specimens.

19. C.Culture media based on applications
7.Anaerobic media:
• Anaerobic media is mainly supplemented with hemin and
vitamin K where bacteria need Low oxygen content,
reduced oxidation–reduction potential and extra nutrients for
their growth.
• The media is also contains 1% glucose, 0.1% thioglycollate,
0.1% ascorbic acid, 0.05% cysteine or red hot iron filings.
• Before use the medium is to be boiled in water bath to
expel any dissolved oxygen and then sealed with sterile
liquid paraffin.
• Example: Robertson Cooked Meat (RCM) medium is
commonly used to grow Clostridium spps. contains a 2.5 cm
column of bullock heart meat and 15 ml of nutrient broth.
• Thioglycollate broth contains sodium thioglycollate, glucose,
cystine, yeast extract and casein hydrolysate.

20. C.Culture media based on applications
8.Assay Media:
• These media is used for assay of
amino acids, vitamins and
other antibiotics.
• Antibiotic assay media are used
for determination of antibiotic
potency (by microbial assay).