1. TYPES OF culture MEDIA
SUBMITTED TO:- SUBMITTED BY:-
Dr. Suman Upadhyaya Anikesh Kr. Singh
M.Sc. FMT (1stSem)
DEM - BBAU
2. CULTURE MEDIUM
The food material on which microorganisms
are grown in the laboratory is known as
medium (pl. media) and the growth itself is
called a culture.
3. Types of culture media
Culture media can be classified on the basis of
following characterstics:
I. Consistency
II. Composition
III. Purpose
4. I. ON THE BASIS OF consistency
1. Solid medium
2. Semi-solid medium and
3. Liquid medium
5. 1. SOLID MEDIum
'Agar' is most commonly used to prepare
solid medium.
Solid medium contains agar at a
concentration of 1.5-2.0%.
Agar is golden-yellow granular
powder obtained from seaweed.
6. CONT…
It is basically a polysaccharide extract.
Agar is an ideal solidifying agent as it is :
• Bacteriologically inert, i.e. no influence on
bacterial growth.
• It remains solid at 37°C.
• It is transparent.
7. Cont…
Solid medium has physical structure and allows
bacteria to grow in physically informative or
useful ways (e.g. as colonies or in streaks).
Advantages of solid media:
• Bacteria may be identified by studying the colony
character.
• Mixed bacteria can be separated.
• Solid media is used for the isolation of bacteria as
pure culture.
8. 2. Semi-solid medium
They are prepared with agar at concentrations
of 0.5% or less.
They have soft custard like consistency.
They are useful in demonstrating bacterial
motility and separating motile from non-
motile strains.
9.
10. 3. Liquid medium
They are sometimes referred as “ broth”.
These media contains specific amounts of
nutrients but don’t have any trace of gelling
agents such as gelatin or agar.
Broth medium serves various purposes such
as propagation of large number of organisms,
fermentation studies, and various other tests.
e.g. sugar fermentation tests.
11. Cont…
It is difficult to identify all type of
microorganisms in liquid medium.
Suitable for the isolation of bacteria from
blood culturing and water analysis.
12. II. ON THE BASIS OF COMPOSITION
1. Synthetic or chemically defined medium:-
A chemically defined medium is one
prepared from purified ingredients and
whose exact composition is known.
It provides trace elements and vitamins
required by the microbe and especially a
defined carbon and nitrogen source.
13. CONT…
Glucose or glycerol are often used as carbon
sources, and ammonium salts or nitrates as
inorganic nitrogen sources.
eg: peptone water –
1% peptone + 0.5% NaCl in water.
14. 2. Non synthetic or chemically undefined medium:-
Non-synthetic medium contains at least one
component that is neither purified nor completely
characterized.
Undefined medium has some complex ingredients,
such as yeast extract, which consists of a mixture of
many, many chemical species in unknown
proportions.
For example- Nutrient broth, is derived from
cultures of yeasts
15.
16. III. ON THE BASIS OF PURPOSE
1. General purpose media/ Basal Media.
2. Enriched medium.
3. Selective medium.
4. Differential/ indicator medium.
5. Transport media.
6. Anaerobic media.
7. Assay media.
17. 1. Basal media
Basal media are basically simple media that
supports most non-fastidious bacteria.
Peptone water, nutrient broth and nutrient
agar are considered as basal medium.
These media are generally used for the
primary isolation of microorganisms.
19. 2. Enriched medium
Addition of extra nutrients in the form of
blood, serum, egg yolk etc, to basal medium
makes them enriched media.
Enriched media are used to grow nutritionally
exacting (fastidious) bacteria.
20. Cont…
Blood agar, chocolate agar, Loeffler’s serum
slope etc., are few of the enriched media.
Blood agar is prepared by adding 5-10% (by
volume) blood to a blood agar base.
Choclate agar is also known as heated blood
agar or lysed blood agar.
22. 3. Selective medium
Selective and enrichment media are designed
to inhibit unwanted commensal or
contaminating bacteria and help to recover
pathogen from a mixture of bacteria.
While selective media are agar based,
enrichment media and are liquid in
consistency.
23. Cont…
Any agar media can be made selective by
addition of certain inhibitory agents that don’t
affect the pathogen of interest.
Various approaches to make a medium
selective include addition of antibiotics, dyes,
chemicals, alteration of pH or a combination
of these.
24. Cont…
Examples of selective media include:
• Thayer Martin Agar used to recover N.gonorrhoeae.
• It usually contains the following combination of
antibiotics:
Vancomycin: which is able to kill most Gram-positive
organisms.
Colistin,: which is added to kill most Gram-negative
organisms except Neisseria.
Nystatin,: which can kill most fungi.
Trimethoprim: which inhibits Gram-negative
organisms.
25. Cont…
• Eosin methylene blue: selective for gram
negative bacteria
The dye methylene blue in the medium inhibit
the growth of gram positive bacteria
26. Cont…
• Lowenstein –Jenson medium is a
solid medium used for
Mycobacterium tuberculosis.
It contain penicillin, nalidixic
acid and malachite green to
inhibit growth of gram positive
and gram negative bacteria, in
order to limit growth to
Mycobacteria species only.
27. Cont…
• Mannitol Salt Agar and Salt Milk Agar used to
recover S.aureus contains 10% NaCl.
• Selective media such as TCBS Agar used for
isolating V. cholerae from fecal specimens
have elevated pH (8.5-8.6), which inhibits
most other bacteria.
28. Cont…
• MacConkey’s Agar used
for Enterobacteriaceae members contains bile
salt that inhibits most gram positive bacteria.
• Wilson and Blair’s Agar for recovering S.
typhi is rendered selective by the addition of
dye brilliant green.
29. 4. Differential/ indicator medium
Certain media are designed in such a way that
different bacteria can be recognized on the basis
of their colony colour.
Various approaches include incorporation of
dyes, metabolic substrates etc, so that those
bacteria that utilize them appear as differently
coloured colonies.
Differential media allow the growth of more than
one microorganism of interest but with
morphologically distinguishable colonies.
30. Cont…
Examples of selective media include:
a) MacConkey medium: Distinguish between
lactose fermenters & non lactose fermenters.
• Lactose fermenters – Pink colonies
• Non lactose fermenters – colorless colonies
31. Cont…
b) Xylose Lysine Deoxycholate Agar(XLD): Used
for the recovery of Salmonella and Shigella
species.
32. Cont…
c) Cysteine Lactose Electrolyte Deficient
Agar(CLED): For cultivation of pathogen from
urine specimen, inhibit swarming of proteus sp.
CLED, serratia
33. 5. Transport media
Transport media is used for transporting the
samples.
Clinical specimens must be transported to the
laboratory immediately after collection to
prevent overgrowth of contaminating
organisms or commensals.
This can be achieved by using transport
media.
34. Cont…
Such media prevent drying (desiccation) of
specimen, maintain the pathogen to
commensal ratio and inhibit overgrowth of
unwanted bacteria.
Eg:
– Stuart’s medium
– Buffered glycerol saline
35. Cont…
Cary Blair transport medium and
VenkatramanRamakrishnan (VR) medium are
used to transport feces from suspected
cholera patients.
Sach’s buffered glycerol saline is used to
transport feces from patients suspected to be
suffering from bacillary dysentery.
Pike’s medium is used to transport
streptococci from throat specimens.
36. 6. Anaerobic media
These media are used to grow anaerobic
organisms.
Anaerobic bacteria need special media for
growth because they need low oxygen
content, reduced oxidation –reduction
potential and extra nutrients.
Media for anaerobes may have to be
supplemented with nutrients like hemin and
vitamin K.
37. Cont…
Such media may also have to be reduced by
physical or chemical means.
Addition of 1% glucose, 0.1% thioglycollate,
0.1% ascorbic acid, 0.05% cysteine or red hot
iron filings can reduce dissolve oxygen.
Before use the medium must be boiled in
water bath to expel any dissolved oxygen and
then sealed with sterile liquid paraffin.
38. Cont…
Example of anaerobic media are:
Robertson Cooked Meat (RCM) medium is
commonly used to grow Clostridium spps.
Thioglycollate broth contains sodium
thioglycollate, glucose, cystine, yeast extract and
casein hydrolysate.