This file will tell how chemical agents control microbial growth?

1. CONTROL BY THE CHEMICAL AGENTS
(PHENOL AND PHENOLIC COMPOUNDS)
Presenter Name : Muhammad ISMAEEL
Roll no : 873 (023791)
Supervisor Name :Professor Fazal Elahi Butt
Subject : Microbiology

2. (1) Sterilization. The process of destroying all forms of microbial
life. A sterile object, in the microbiological sense, is free of living
microorganisms. The term ssterile, sterilize, and sterilization
therefore refer to the complete absence or destruction of all
microorganisms and should dnot be used in a relative sense. An
object or subssubstance sterile or nonsterile; it can never be
semisemisterile almost sterile.
(2) Disinfectant. An agent, usually a chemical, that kills the growing
forms but not necessarily the resistant spore forms of isease-
producing mmicroorganisms.The term is commonly applied to
substances used on inanimate objects. Disinfect is the process of
destroying infectious agents.
(3) Bactericide. An agent that kills bacteria (adjective, bactericidal).
Similarly, the terms fungicide, virucide, and sporicide refer to
agents that kill fungi, viruses, and spores, respectively.
DEFINITION OF IMPORTANT TERMS

3. (4) Antiseptic. A substance that opposes sepsis, i.e., prevents the
growth or action of microorganisms either by destroying
microorganisms or by inhibiting their growth and metabolism.
Usually associated with substances applied to the body.
(5) Germicide (Microbicide). An agent that kills the growing forms
but not necessarily the resistant spore forms of germs; in practice a
germicide is almost the same thing as a disinfectant, but germicides
are commonly used for all kinds of germs (microbes) for any
appapplication.
(6) Sanitizer. An agent that reduces the microbial population to safe
levels as judged by public health requirements. Usually it is a
chemical agent that kills 999. percent of the growing bacteria.
Sanitizers arecommonly applied to ininanimate objects and are
generally employed in the daily care of equipment and uteutens in
dairies and food plants and for glasses, dishes, and utensils in
restaurants.

4. (7) Bacteriostasis. A condition in which the growth of bacteria is
prevented (adjective, bacteriostatic). Similarly, fungistatic
describes an agent that stops the growth of fungi. Agents that
have in common the ability to inhibit growth of microorganisms
are collectively designated microbistatic agents.
(8)Antimicrobial Agent.One that interferes with the growth and
metabolism of microbes. In common usage the term denotes
inhibition of growth, and with reference to specific groups of
organisms such terms as antibacterial or antifungal are frequently
employed. Some antimicrobial agents are used to treat infec tions,
and they are called chemotherapeutic agents.

5. THE SELECTINS OF A CHEMICAL AGENT FOR
PRACTICALAPPLICATIONS
(1) Nature of the material to be treated. To cite an extreme example, a
chemical agent used to disinfect contaminated utensils might be quite
unsatisfactory for application to the skin; i.e., it might do serious injury to
the tissue cells. Consequently, the substance selected must be compatible
with the material to which itis applied.
(2) Types of microorganisms . Chemical agents are not all equally effective
against bacteria, fungi, viruses, and other microorganisms. Spores are more
resistant than vegetative cells. Differences exist between Gram-positive and
Gram-negative bacteria; Escherichia coil is much more resistant to cationic
disinfectants than Staphylococcus oureus. Differences in action also exist
between strains of the sams species. Therefore, the agent selected must be
known to be effective against the type of organism to be destroyed

6. 3 Environmental conditions. The factors temperature,
pH, time, concentration, and presence of extraneous
organic material, may all lhave a bearing on the rate and
efficiency of antimicrobial action. The successful use of an
antimicrobial agent requires an understanding of the
influence of these conditions on the particular agent, so it
can be employed under the most favorable circumstances.

7. MAJOR GROUPS OF CHEMICAL ANTIMICROBIAL
AGENTS
The major antimicrobial agents can be grouped as shown below. We will
discuss representative examples from each of these groups.
1. Phenol and phenolic compounds
2. Alcohols
3. Halogens
4. Heavy metals and their compounds
5. Dyes
6. Detergents
7. Quaternary ammonium compounds
8. Aldehydes
9. Gaseous agents

8. • Phenol has the distinction of being used successfully in the
1880s by Joseph Compounds Lister, a surgeon, to reduce
infection of surgical incisions and surgical wounds.
• Accordingly, he instituted the practice of applying a solution
of phenol (carbolic acid) to surgical incisions and wounds.
• The reduction in infections was striking. Later he developed
the practice of spraying phenol iint the operating room area
to control infection.
PHENOL AND PHENOLIC COMPOUNDS

9. • Phenol and phenolic compounds are very effective disinfectants. A 5%
aqueous solution of phenol rapidly kills the vegetative cells of microorganisms
spores are much momo resistant.
• Many derivatives of phenol have been prepared and evaluated for their
antimicrobial activity. The chemical structures of phenol and a few phenol
derivatives are as follows.
o-Pnenylphenol

10. • Hexylresorcinol, a derivative of phenol, is marketed in a
solution of glycerin and water.
• It is a strong surface-tension reductant, which may
account in papar for its high bactericidal acactivity.
commercial product containing hexyresorinol, ST.37, is so
named because of its surface-tension value.
• Hexyiresorcinol preparations preparations are employed
as general antiseptics.
Hexylresorcinal
Hexachlorophene

11. PRACTICAL APPLICATIONS
• Phenolic substances may be either bactericidal or bacte-
• riostatic, depending upon the concentration used.
• Some phenolics are highly fungicidal. The antimicrobial activity of phenolics is
reduced at aa alkaline pH and by organic material. Low temperatures and the
presence of soap also reduce antimicrobial activity.
• Aqueous solutions of from 2 to 5% can be employed tt disinfect such materials
as sputum, urine, feces, and contaminated instruments or utensils
• However, derivatives of phenol diluted in detergents or some other carrier find
use in many commercial antiseptic and disinfectant preparations.
• One of the widely used phenolic derivatives is o-phenylphenol. Combination of
compounds of this class with detergents results in products with good
disinfectant as well as detergent properties.

12. MODE OF ACTION
• Exposure of microbial cells to phenolic compounds produces a variety of
effects.
• Depending upon the concentration of the phenolic compound to which
microbial cells were exposed, researchers have described results such as
disruption of cells, precipitation of cell protein, inactivation of enzymes,
and leakage of amino acids from the cells.
• Although the specific mode of action is not clear, there is a consensus
that the lethal effect is associated with physical damage to the membrane
structures in the cell surface, which initiates further deterioration.

13. ANY QUESTION OR
Comment

14. THANKS FOR
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