What is medical microbiology ? And technique how to play with microorganisms.

1. Submitted T o : Presented by :
Rinki mishra Ankit sharma
B.Sc. IIyr
Dr. B. Lal Institute of Biotechnology

2.  Medical microbiology is both a branch of medicine and microbiology .
 The branch of microbiology which deals with the characterization, prevention &
control of disease-producing microorganisms in human beings is called Medical
Microbiology.
It deals with the infectious agents which cause diseases in man. It explain the bodily
mechanisms that help fight disease.

3. INSTRUMENTS
 INCUBATOR
Incubator Digital Weighing Balance Laminar Air FLow
Autoclave PH Meter

4. Preparation of Culture Media
Isolation of Microorganism form clinical sample
1. Serial Dilution
2. Pour plate
3. Spread Plate
4. Streaking
Characterization & Identification
Morphological
Microscopic
Biochemical
Antibiotic susceptibility test

5.  COMPLEX :– contains ingredients of unknown
chemical composition.
e.g. Potato dextrose agar.
 DEFINED :– All chemical compositions are known.
e.g. Czapek dox medium
 SELECTIVE: - suppress unwanted microbes or
encourage desired microbes.
e.g. Endo agar, EMB, Mac Conkey agar
TYPES OF MEDIA
Culture Media :
Contains all the nutrients required for the growth of microbes.
Mac conkey agar
Nutrient agar

6. SELECTIVE :-
Suppress unwanted microbes or encourage desired microbes.
e.g. BLOOD AGAR
DIFFERENTIAL MEDIA: –
Distinguish colonies of specific microbes from others.
e.g. Endo agar, EMB, Mac Conkey agar.
ENRICHED MEDIA :–
Designed to increase the number of desired microbes to a detectable level.
e.g. Blood agar.

7. AIM:– To obtain pure colonies of microbes
SERIAL DILUTION METHOD – Inoculum subjected to serial dilution in
normal saline , then spreading is done on agar plates.

8.  POUR - PLATE METHOD –
 In this, successive dilutions of
inoculum is added to molten agar in
respective petriplates.
 Individual colonies are picked for sub
culturing.
SPREAD – PLATE METHOD –
 In this, dilute sample is placed onto
solidified agar and is spread uniformly
with sterile ,bent glass rod.

9. streak plate method.
Principle:
The streak plate methods often a most practical method of obtaining a discrete colonies and pure culture. It
was originally developed by two Bacteriologist LOE LUEFF LOEFFLAR and GAFFKY in the laboratory
of Robert Koch. In this method the satirized loop or transfer needle is dipped into a suitable diluted
suspension of organisms which is already solidified in agar plate to make a series of parallel non-overlapping
streaking.
There are two type of Streaking
1) With Intermediate heat 2) Without Intermediate heat
A) Radial streaking A) Continuous Streaking
Results:-
A confluent growth was seen where the initial streak was made, the
growth is less dense away from the streak & discrete colonies farthest
away from the streak (i.e. end of the streak)
Figure: Streaking

10. When grown on a variety of media, microorganism will exhibits differences in the
macroscopic appearance of their growth. These differences called cultural
characterstics are used as a basis for separating microorganisms into taxonomic
groups.
Morphological Characteristics of Microorganism
Irregular
circular

11. • Gram Staining :
 Used to differentiate b/w gram +ve & gram –ve bacteria.
 Based on the difference in the composition of bacterial cell
walls.
• Primary Stain – Crystal Violet
• Mordant - Iodine
• Secondary Stain - Saffranin
 Result :- gram +ve cell appears purple colour & gram –ve
appearing pink colour.
 Purple color : gram positive
 (Staphylococcus)
 Pink color : gram negative
(E. coli)
• Negative Staining
 The acidic dye - INDIA INK OR NIGROSINE
(acidic dye)
• Does not stain the bacteria but stains the
background.
• Result :- spherical cells of staphylococcus aureus
occurring single as well as cluster appear.
Transparent (color less) against blue background
Negative Stain
Gram positive

12.  IMViC TEST
This includes : -
1. INDOLE TEST :
a) Medium : TRYPTONE BROTH
Tryptophan + tryptophanase = indole +
pyruvic acid
b) Interpretation : Cultural tube +
Kovac’s reagent
Red layer : positive test (E.coli)
Yellow or brown : negative
test(Klebsiella Psuedomonas)
2.METHYL RED TEST:
a) Medium : MRVP Broth
It is based on the fermentation
product of glucose .
b) Interpretation :-
Cultural broth + methyl red
red layer : positive test
(Pseudomonas)
yellow layer : negative test
(Klebseilla)
3.VOGES - PROSKAUER TEST
Identifies bacteria that ferment
glucose into 2,3 –
butanediol.
Medium : MRVP Broth
Interpretation : cultural broth
+ Barritt’s reagent ; if
cherry red : positive test
(Klebseilla)
if colour absent :- negative
test (Pseudomonas)
Figure: Voges – Proskauer
Figure: Methyl Red TestFigure: Indole test

13. Citrate Utilisation Test
 Based on the ability to use citrate as
source of energy.
 Medium : SIMMON’S CITRATE AGAR
 Interpretation : -
Blue : positive test ( Pseudomonas) No
color change : negative test (E.coli).
Catalase test :

Based on the ability to use catalase as source of
energy.
Medium: Hydrogen peroxide
 Interpretation: –
Air bubbles = +ve test (staphylococcus sp.)
Figure: - Catalase testFigure: -Citrate Utilisation test

14.  Antibiotics susceptibility testing
 Principle:This test determines the susceptibility of a microbial species against different antibiotic
agents.
The test is performed by the commonly used Agar Diffusion Method which is designed to determine
the smallest amount of the antibiotic needed to inhibit the growth of micro-organism
Figure: - Testing of anti-biotics activity Disk Diffusion Method
Erythromycin E
Vancomycin VA
Levofloxacin LE
Penicillin P
Ampicillin AMP

15. THANK YOU…