CLASSES OF ANTIMICROBIAL AGENTS

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  • Antiseptics: Antiseptics are antimicrobial agents which inhibits the growth and development of microorganisms on the body surface of living things. They are routinely used as topical agents on wounds, and for application to skin, and mucous membranes of living things. They are used on the body surfaces of animates because of their anti-infective effects. Unlike, a disinfectant which may have a harsh effect on the human skin, antiseptics has a milder effect on the body. The spectrum of activity of antiseptics may be either bacteriocidal or bacteriostatic. They are applied on the surfaces of wounds after injury and routinely used on the skin prior to injection or surgical operations. Antiseptics can sometimes be used on inanimate objects such as furniture for disinfection. Typical examples of antiseptics include water, boric acid, hydrogen peroxide, alcohol such as ethanol or isopropanol, iodine, benzalkonium chloride, chlorhexidine, hexachlorophene and mercury compounds. Generally, antiseptics are used to prevent the growth of microbes near burns, cuts and wounds; and they keep germs from growing on animate things. Antiseptics do not destroy resistant bacteria spores. They are used to achieve antisepsis on animate tissues.  
  • Disinfectants: Disinfectants are antimicrobial agents that are used on the surface of inanimate objects such as furniture, table, floor and door handles to kill or inhibit the growth of microbes on them. Antimicrobial agents that are disinfectants only destroy some organisms and not necessarily all forms of microbes. They do not destroy resistant bacterial spores. Disinfectants are used to achieve disinfection on inanimate objects. The mode of action of disinfectants is basically based on their ability to destroy the cell wall of microbes. They also interfere with the metabolism and/or metabolic processes of microorganisms, thereby disrupting their growth. The mechanism of action of disinfectants is also akin to the mechanisms of action of antiseptics. Disinfectants are frequently used in hospitals to disinfect the floors, bed linings, door handles, toilets and other equipment used in the hospital environment. They are also used in the home to disinfect utensils, floors, and furniture. Typical examples of disinfectants include formaldehyde, phenolic compounds, sodium hypochlorite (bleach).
  • Preservatives: Preservatives are antimicrobial agents that are added to food, beverages, drugs/medications, cosmetics and other biological agents in order to either prevent their spoilage due to microbial growth in them or to prevent undesirable change in their composition or quality. They are added to these products during their production. Preservatives possess no health benefits. They only prevent or slow the growth of microbes in food products and medications as well as in any other products they are incorporated. Preservatives prevent food degradation by microbes such as bacteria and fungi in canned food products. Preservatives can either be naturally sourced or synthetically produced. Examples of preservatives include lactic acid, citric acid and ascorbic acid.
  • Sterilants: Sterilants are antimicrobial agents that kill microbes on the surface of inanimate objects. They have a broader spectrum of activity than preservatives. A sterilant is a chemical or physical process that is applied to inanimate objects to kill all microorganisms as well as spores. Examples of sterilants are ethylene oxide (EtO) and glutaraldehyde. Sterilants are capable of completely eliminating or destroying of all forms of microbial life, including spores.EtO is mainly used to sterilize moisture and heat-sensitive instrument in hospitals and in the industry. However, the use of EtO should be done with caution since the gas poses several health hazards that requires special training, handling and disposal of the chemical in its use. EtO is a potential human carcinogen with a plethora of acute and chronic health effects. Glutaraldehyde is not a human carcinogenbut it also posessome untoward effects that are more benign than the EtO gas.

FURTHER READING

Ashutosh Kar (2008). Pharmaceutical Microbiology, 1st edition. New Age International Publishers: New Delhi, India. 

Block S.S (2001). Disinfection, sterilization and preservation. 5th edition. Lippincott Williams & Wilkins, Philadelphia and London.

Courvalin P, Leclercq R and Rice L.B (2010). Antibiogram. ESKA Publishing, ASM Press, Canada.

Denyer S.P., Hodges N.A and Gorman S.P (2004). Hugo & Russell’s Pharmaceutical Microbiology. 7th ed. Blackwell Publishing Company, USA. Pp.152-172.

Ejikeugwu Chika, Iroha Ifeanyichukwu, Adikwu Michael and Esimone Charles (2013). Susceptibility and Detection of Extended Spectrum β-Lactamase Enzymes from Otitis Media Pathogens. American Journal of Infectious Diseases. 9(1):24-29.

Finch R.G, Greenwood D, Norrby R and Whitley R (2002). Antibiotic and chemotherapy, 8th edition. Churchill Livingstone, London and Edinburg.

Russell A.D and Chopra I (1996). Understanding antibacterial action and resistance. 2nd edition. Ellis Horwood Publishers, New York, USA.

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