Prof.Mr.Kiran K. Shinde (M.Pharm), Assistant professor (VNIPRC) Pharmaceutical microbiology (Second year b.pharm) (3rd semester) Introduction Classification & mode of action of disinfectant Factors affecting disinfectant, antiseptics & their evaluation Evaluation of bacteriostatic & bactericidal

1. DISINFECTANT
• Introduction
• Classification & mode of action of disinfectant
• Factors affecting disinfectant, antiseptics & their
evaluation
• Evaluation of bacteriostatic & bactericidal
Prepared by,
Prof. Shinde Kiran (M.Pharm)
Assistant Professor (VNIPRC)
Pharmaceutical Microbiology-I
Second Year B.Pharm
IIIrd Semester
Vidya Niketan Institute
Of Pharmacy & Research
Centre, Bota

2. Introduction
 Disinfection: It is the process of destruction or removal of micro-organisms and reducing
them to a level not harmful to health.
 Disinfection generally kills the sensitive vegetative cells but not the heat – resistance
endospores.
 Disinfectants are usually bactericidal but occasionally they may be bacteriostatic.
 It plays an important role in control of microbial contamination and prevention of infection.
 If the object is lifeless like the areas, dishes, floor, etc the chemical agent is used and called
is disinfectant.

3.  Ideal disinfectant should have following properties:
1. Broad spectrum
2. Non toxic
3. Odourless
4. Fast acting
5. Economical
6. Surface compatibility
7. Easy to use
8. Solubility and miscibility
9. Stable on storage
10.Not affected by physical factors

4. 1. Acids & Alkalis
2. Halogens
3. Heavy metals
4. Phenol & its derivatives
5. Alcohols
6. Aldehydes
7. Dyes
8. Detergents & Soaps
9. Quaternary ammonium compounds
Classification & Mode of Disinfection

14. Factors affecting disinfectant action
1. Concentration of disinfectants
2. Temperature
3. Time of contact
4. pH of the environment
5. Surface tension
6. Formulation of the disinfectant
7. Chemical structure of disinfectant
8. Type & number of micro-organisms present
9. Interacting substances in the environment
10. Potentiation synergism & antagonism of disinfectants

15. 1. Concentration of disinfectant: The rate of killing of micro-organisms varies
directly with the concentration of the disinfectant. Concentration exponent
or dilution coefficient is an important characteristic of each disinfectant and is useful in
determining the effect of dilution on the disinfectant.
Where, n is conc. Exponent / dilution coefficient for disinfectant
t1 is death time with conc. C1
t2 is death time with conc. C2
2. Temperature: The rate of disinfection normally increases with the
temperature. This bactericidal activity may be expressed by temperature coefficient .the
rise in temperature is denoted by q where, 10 ‘C per rise in temp. is q 10 or Q 10
Where, t1 & t2 are two temperature
differing 10 ‘C

16. 3. Time of contact: Sufficient time of contact must be allowed for the disinfectant
4. pH of environment: A change of pH during the disinfection process can affect the rate of
growth of inoculum
5. Surface tension: The contact between aqueous solutions of disinfectant is facilitated if they
have surfactant properties. This helps in adsorption of surface active disinfectants
on the surfaces of cells
6. Formulation of the disinfectant: This may be important for the effective use of disinfectants.
7. Type & no. of micro-organisms present: The efficiency of disinfection greatly depends on the
nature & no. of containing microorganisms & specially on the presence or absence of bacterial
spores.

17. 8. Chemical structure of disinfectant: Chemical structure of compounds affects the disinfectant
activity.
9. Interfering substances in the environment: Material such as blood, body fluids, pus, milk, food
residues or colloidal proteins may reduce the
effectiveness of disinfectant. This may be due to adsorption or chemical interaction from adequate
contact with germicide.
10. Potentiation, synergism & antagonism of disinfectant: Potentiation of a disinfectant leads to
enhanced antimicrobial activity.
Synergistic effects are often shown by 2 antimicrobial agents which is giving an increased activity.
Antagonism leads to decreased antimicrobial activity and use is made of antagonism in the
elimination of antimicrobial properties of materials.

18. Factors affecting Antimicrobial Agent
1. Properties of chemical agents
2. Environment
3. Types of micro-organisms
4. Intended application
5. Toxicity of agents
6. Cultural state

19. Evaluation of Antimicrobial agents & Disinfectants
[Bacteriostatic & Bactericidal]
Methods or Techniques used in evaluation
of disinfectant
2. Filter paper
and cup plate
method
1. Tube Dilution
and agar plate
method
5. Kelsey Sykes
method
3. Ditch – plate
method
4. Phenol
coefficient
method
Bacteriostatic: Kills the organism
It includes Serial fluid & solid media method
Cup plate method
Ditch plate method, etc.
Bactericidal: Inhibits the growth
It includes Phenol Co-efficient method, etc.

24. Advantages Disadvantages
1. They are inexpensive can be
performed easily
2. They supply standards for crude
properties.
3. they give reproducible results in the
hands of experienced workers.
1. These tests do not give any
information related to tissue toxicity
2. Sampling errors are large in phenol
coefficient tests.
3. Phenols coefficient test do not give
any indication of the effects of
dilution on the activity of
disinfectant

26. Thank-you