pathology

1. CULTURE MEDIA

2. Bacteria have to be
grown [cultured] for
them to be identified.

3. Study of bacteria
involve the study of
bacterial
populations.

4. Louis paster –Original
media
Earliest solid medium-
cooked cut potato-
Robert Koch.

5. Disadvantages of liquid
media
1.Bacteria growing in
liquid media may not
exhibit specific
characteristics for their

6. 2.Difficult to isolate
different types of
bacteria from
mixed populations.

7. 3.Bacteria grow
diffusely in liquids
they produce
discrete visible
growth in solid
media.

8. Uses of liquid media
1.obtained bacterial
growth from blood on
water when large
volumes have to be
tested.

9. 2.For preparing bulk
cultures for antigens
or vaccines.

10. Solid media
Distinct colony morphology
exhibit may other
characteristic features

11. 1.Agar
Universaly used for
preparing solid media.

12. Chief constituents:
Long chain poly
saccaharide.
Inorganic salts.
Protein like
substance.

13. not affected by
growth of
bacteria.

14. Agar is
hydrolysed at high
temperatures at
high acid/alkaline
pH.

15. It melts at 98.C and
usually sets at 42.C.
depending on agar
concentration : 2%
agar is used for solid
media.

16. The jellifying
property varies in
difference brand.
It manufactured
powder.

17. 2.Peptone media –
Universaly used common
media.
Complete mixture of
partially digested proteins.

18. Its constituents :
Proteoses
Poly peptides
Aminoacids
Inorganic salts –
Phosphates, K+, Mg+

19. Accessary growth
factors-
Riboflavin
Difficult brands show
appreciable differences
in composition of
growth promoting

20. Special brands:
oNeopeptone
oProteose peptone
oDigest broth
oMeat extract – Lab-Lemco
oBlood,Serum and yeast
extract

21. TYPES
1.
•Solid media
•Liquid media
•Semisolid media

22. 2.
Simple media
Complex media
Synthetic media /
Defined media
Semi defined media

23. Special media
-Enriched media
-Enrichment media
-Selective media
-Indigator /
Differential media
-Super media
-Transport media

24. 3.
Aerobic media
Anaerobic media

25. 1.Simple media
[Basal media]
Eg: Nutrient broth
It consist of
peptone.

26. Meat extract, NaCl and
H2O
Nutrient agar made by
adding 2% agar
 Most common
medium in routine
diagnostic laboratories.

27. Agar concentration is 0.2-
0.5% - semisolid /sloppy agar
is obtained which enables
motile organisms to spread.
6% agar concentration –
prevents spreading by
organisms.
Eg:Proteus

28. 2.Complex media
These use for special
purposes / certain
characteristics / providing
special nutrients required
for the bacterial growth
under study.

29. 3.Synthetic /defined
media
These prepared from
pure chemical
substances.
It was for special study
like metabolic

30. Eg:Simple peptone
water medium – 1%
peptone with 0.5%
NaCl in H2O may be
considered a semi
defined medium.

31. 4.Enriched media
In these media
substances such as
blood or egg added
to a basal media.

32. They are used to grow
bacteria which are
exactly in their
nutritional needs.
Eg: Blood agar,
chocolate agar,egg
media.

33. 5.Enrichment media
In mixed cultures / in
materials containing >1
bacterium, the bacterium to
be isolated.

34. Usually non pathogenic /
commensal bacteria tend
to over grow the
pathogens
Eg:Typhi being overgrown
by E.Coli in cultures from
faeces.

35. In this situations
substances which have a
stimulates effect on the
bacteria to be grown or
an inhibitory effect on
those to be suppressed
are added to a liquid
medium.

36. Such substances are
added to a liquid
medium.
Results-Absolute
increase in the numbers
of the wanted bacterium

37. Eg:Tetrathionate broth –
Tetrathionate inhibits
coliforms which allowing
typhoid, parathyphoid
bacilli to grow freely.
Selenite F broth –
dysentery bailli

38. 6.Selective media
As in the entrichment
media, if the inhibiting
substance is added to a
solid media.
Eg:Desoxycholate citrate
media – for dysentery

39. 7.Indicator media
It contain an
indicator which
changes colour when
a bacterium grows in
them.

40. Eg: Incorporation
of sulphite in
Wilson and Blair
media.

41. 8.Differential media
The media enabling it
to bring out difference
characteristics of
bacteria and helping to
distinguish between
them.

42. Eg: Mac Conkey’s media-
Peptone, Lactose, Agar,
Nutral red and taurocholate.
Shows up lactose
fermenters as pink colour
while non lactose
fermenters are
colourless/pale.

43. Eg:
Nagler’s media-to view
lecithinase activity.

44. 9.Sugarmedia
The term sugar-In
microbiology denotes
any fermentable
substance.

45. 1.Monosaccharides : Pentose-
Arabinose,Xylose
Hexoses-Dextrose,Mannose
2.Di saccharides-Saccharose,
Lactose
3.Poly saccharides-Starch,
Insulin
4.Tri saccharides-Raffinose
5.Alcohols-Glycerol, Sorbitol
6.Glucosides-Salicin

46. Usual sugar media
1% sugar in peptone water
along with an appropriate
indicator.
A small tube [Durham’s
tube] is kept invertes in the
sugar tube to detect gas

47. For organism which
are exacting in their
growth requirements.
Eg:Pneumo cocci-Hiss
serum sugars are
used-3% serum.

48. 10.Transport media
In the case of delicate
organisms
Eg: Gono cocci which may
not survive the taken for
transporting the specimen
to the lab or may be over
grown by non pathogens

49. Eg:Dysentry/Choler
a organism in
faeces
Special media are
used to transport
specimens.

50. Eg: Stuart’s media
-Non nutrient soft agar
gel
-Reducing agent to
prevent oxidation and
charcoal to neutrilise
certain bacterial
inhibitors.

51. 11.Anaerobic media
Used to grow the
anaerobic organisms
Eg:Robertson’s
cooked meat media

52. Indications for culture
•Isolate bacteria in pure
culture
•Demonstrate their
properties.
•Obtain sufficient growth
for preparation of Antigens
for other tests.

53. •Determine sensitivity to
antibiotics.
•Estimate viable count.
•Maintain stock cultures.