Disinfectants
Classify disinfectants and name the chemical agents used for skin antisepsis. Describe the steps of performing
hand hygiene
Definition
Chemical agents designed to inactivate or destroy microorganisms on inert surfaces.
Classification
Air disinfectants
Alcohols
Aldehydes
Oxidizing agents
Peroxy and peroxo acids
Phenolics
Quaternary ammonium compounds
Inorganic compounds
Chlorine
Iodine
Acids and bases
Metals
Terpenes
Other
Non-chemical
Chemical Agents
The chemical agents are classified as
- Acids and alkalies
Strong acids and alkali kill the bacteria but weakorganic acids injibit their growth
- Halogens
Chlorine, fluorine, bromine and iodine in the free state as well as their compounds strongly act as germicidal
- Heavy metals
The most widely used heavy metals are those of mercury, silver and copper. High concentration of salts of heavy metals like mercury copper and silver coagulate cytoplasmic proteins, resulting in the damage or death of cell
- Phenol and its derivatives
Phenol is thechief products obtained by the distillation of the coal tar.
Phenol 1% has bactericidal action.
Many derivatives of phenol are more effective and less costly.
- Alcohols
Alcohols have fairly rapid bactericidal action against vegetative bacteria when diluted to the concentration of 60% to 70% v/v with water.
Ethanol 60 to 70 % and isopropanol 50 to 60 % v/v are used as skin disinfectants while methanol vapour has been used as fungicide.
The higher alcohols (propyl, butyl, amyl etc. ) are more germicidal than ethyl alcohol.
Alcohols are used as preservatives in some vaccines.
- Aldehydes
Formaldehyde (HCHO) is the main aldehyde used for disinfection.
Formaldehyde in solution is useful for sterilization of certain instruments.
- Quaternary ammonium compounds are widely used for the control of microorganisms on floors, walls, nursing homes and other public places.
They are also used as skin antiseptic and as sanitizing agents in dairy, egg and fishing industries.
- Dyes
Basic dyes are more effective batericides than acidic dyes
Acridine and triphenylmethane dyes are commonly used as antimicrobial agents.
- Detergents and soaps
They are widely used as surface active agents, wetting agents and emulsifiers.
They are classified into four main groups such as anionic, cationic, non-ionic and amphoteric
The most important agents : the cationic surface active agents eg: Cetrimide, Benzalkonium chloride etc.
Soaps and sodium lauryl sulfate are anionic compounds: those from saturated fatty acids are for gram negative bacilli and those from unsaturated fatty acids are for gram positive organisms
Nonionic detergents : no significant anti-microbial activity
Amphoteric compounds : properties of anionic surfactants as well as properties of cationic surfactants eg. Tego compounds
Characteristics
Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores;
It is less effective than sterilization, which is an extreme physical or chemical process that kills all types of life.
Mode of Action
Disinfectants work by causing the proteins in the cell wall of the organisms to become damaged and outer layers of the bacteria cell to rupture. The DNA material subsequently leaks out.
By destroying the cell wall of microbes or interfering with their metabolism.
Disinfectants kill more germs than sanitizers.
Factors affecting disinfection
Concentration of disinfectant
Temperature
Time of contact
pH of environment
Surface tension
Formulation of disinfectant
Chemical structure of disinfectant
Types and number of micro-organsisms present
Interfering substances in the environment
Potentiation , synergism, and antagonism of disinvactants
Uses
Disinfectants are used to rapidly kill bacteria. They kill off the bacteria
Disinfectants are frequently used in hospitals, dental surgeries, kitchens, and bathrooms to kill infectious organisms.
Disinfectants are concentrated and are used to clean surfaces like floors and building premises.
Disadvantages
Bacterial endospores are most resistant to disinfectants
Skin Antisepsis
The most commonly used agents :-
Alcohol-based solutions, chlorhexidine gluconate
Iodophors such as povidone-iodine.
Alcohol is an excellent germicidal against bacteria, viruses, and fungi; however it lacks residual germicidal activity.
Hand Hygiene
Key Times to Wash Hands:-
Before, during, and after preparing food
Before and after eating food
Before and after caring for someone at home who is sick with vomiting or diarrhea
Before and after treating a cut or wound
After using the toilet
After changing diapers or cleaning up a child who has used the toilet
After blowing your nose, coughing, or sneezing
After touching an animal, animal feed, or animal waste
After handling pet food or pet treats
After touching garbage
Follow Five Steps to Wash Hands
Wet the hands with clean, running water (warm or cold), turn off the tap, and apply soap.
Lather the hands by rubbing them together with the soap. Lather the backs of hands, between fingers, and under nails.
Scrub hands for at least 20 seconds.
Rinse the hands well under clean, running water.
Dry the hands using a clean towel or air dry them.
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