Question

For the following agents indicate their mode of action to control microbial growth and what the agent is used for?

            Phenolics

            Iodine

            Soaps

            Chlorine

            Ethylene gas

            Ozone

            quats

Answer 1

1. Phenolics : A compound that have phenols ( a benzene ring with an -OH group) as a part of their chemical structure.

Mode of action : Phenolics inhibit microbial growth by a variety of means like denaturing protein , disrupting membrane, precipitation of cellular protein, inactivation of enzyme and leakage of cellular material.

Some naturally occuring phenolics in plants are thymol and eucalyptol.

uses:

Some of the application of phenolic compound are:

i. Cresol (methyl phenol) : used in lysol to sterilize glasswares and to mop the floor in hospital rooms.

ii. Chloroxylenol (dimethyl phenol) : used in dettol as anteseptic.

iii. Hexachlorophane : it is insoluble in water. Used in soap.

2. Iodine: Iodine posses sporicidal activity and is effective against all kind of bacteria. It is also highly fungicidal. As iodine causes skin irritation or staining ,Iodophore ( iodine complexed with organic molecule) is used.

Mode of action: Iodine being a powerful oxidizing agent oxidises the cellular material of microbes. It also causes halogination of tyrosine residues on protein and enzyme thereby imactivating it.

uses: A common iodophore is povidone-iodine . Betadine is commonly used as a hand scrub by medical personell before surgery and also as a tropical antisepsis of patient skin before incission.

3. Soaps: Soaps are salts of long chain fatty acids having both polar and non-polar region.Soaps do not kill or inhibit microbial growth and henace are not considered antiseptic or disinfectant.

Mode of action: Soaps interact with non polar oil and greese to create emulsion in water, loosening and lifting away dirt and microbes from the surface ond skin.

uses: soap mechanically carries away micro-organism ,degerming a surface. Some soaps conatins added bacteriostatic agent, giving the soap an antiseptic or disinfectant property.

4. Chlorine: It is used as a disinfectant and is in the form of Hypochlorite and chloramine.

Mode of action: Hypochlorous acid is formed when hypochlorite or chloramine is added on water due to the excessive release of free chlorine.This hypochlorous acid then decomposes to release nascent oxygen which is a very powerful oxidizing agent and kills the micro-organism by oxidizing the cellular component. It also inactivates the protein and enzymes by direct chlorination.

uses:

a) commonly used as a water disinfectant.

b) calcium hypochlorite is used as a sanitizer in cooking utensils.

c) Bleach is used in swimming pool for disinfectant and also for household purpose.

5.Ethylene Gas: Ethylene oxide is used for gaseous sterilization.

Mode of action: The antimicrobial activity of Ethylene is due to the property of alkylation. It causes alkylation (replacement of hydrogen with alkyl group) of protein, DNA and RNA within cells and as a result preventing normal cellular metabolism and replication.

Uses:

It is used in sterilization of heat sensitive material such as spices, oil and plastics.

6. Ozone: It is a peroxygen- a very powerful oxidizing agent .

Mode of actio : Ozone oxidizes the organic material in bacterial membrane thereby weakening the cell wall leading to cell rupture and killing .

Uses:

a) Ozone is used in drinking water treatment and also municipal water treatment.

b) Food storage and disinfection.

c) Air -borne and Water-borne pathogen treatment.

7. Quats: These are quaternery ammonium salts- a cationic detergent.

Mode of action: They have the ability to insert into the bacterial phospholipid bilayer and disrupt membrane integrity. The antimicrobial property of quats is due to the cationic charge .

uses:

a) Quats are used as anteseptic or to disinfect surfaces.

b) Mixture of quats are also found in house hold cleaners.

c) Thay are also used in skin antiseptic, mouth wash , oral rinses.