UNIT 2 STAINING TECHNIQUES, IMViC tests, METHODS OF STERILIZN, EVALUATION OF METHODS, STERILITY INDICATORS - Copy.pptx
1. UNIT 2
a) Identification of Bacteria using
staining techniques
(Simple, Grams staining, Acid-fast staining)
b) IMViC Tests
- By Ms. Christina V
PHARMACEUTICAL MICROBIOLOGY
9. PRINCIPLE
In this staining two stains are used, the first stain (Crystal violet) is called primary
stain and the second one is called counter stain (safranin).
In gram negative bacteria, the cell wall is thin , multi layered containing high
lipid contents. The crystal violet will stain the entire microbial cells
After Crystal violet, Grams iodine is smeared so that a complex is formed (CV-I
Complex)
After that, alcohol is put and the lipid contents are readily dissolved by alcohol,
resulting in pore formation in the cell wall
This leads to the leakage of the crystal violet iodine complex (CV-I Complex) and
resulting in discoloration of gram negative bacteria (So, now they are colorless)
After this, the counterstain is applied (Safranin) and the cells now appear red/pink
In case of gram positive bacteria, the cell wall is thick, so after decolorization
the cell wall retain the CV-I COMPLEX and appear blue in color
9
24. b) IMViC TESTS
(INDOLE-METHYL RED-VP-CITRATE)
IMViC tests is a series of test which is performed to
identify and differentiate bacteria belonging to family
Enterobacteriaceae
Enterobacteriaceae family contains a large number of
genera that are biochemically related to one another.
E.g. Escherichia, Shigella, Salmonella, Enterobacter,
Proteus, etc
24
88. Z-value or Thermal Reduction Time
It is the measure of change in death rate with change in temperature.
88
89. F-value
It is widely used in food industry
Also called as Unit of LETHALITY but now it is called as “F-
value”
F-value is time in minutes required to kill micro-organisms in a
given food under specified conditions
This value is also used to calculate the probable number of
bacteria that remain after the processing done in food products
89
98. Biological Indicators
They are also known as bio indicators
They are used as potential tool or natural indicator to monitor the
changes in the environment
These are tested in support of sterilization validations and routine
product release of EO sterilization and steam sterilization
98
