Top 8 Antiseptics Used to Destroy Microorganisms | Microbiology

The following points highlight the top eight antiseptics which are used to destroy microorganisms. The antiseptics are: 1. Alcohols 2. Iodine 3. Phenolics and Related Compounds 4. Peroxides 5. Dyes 6. Heavy Metals 7. Quaternary Ammonium Compounds 8. Acids.

Antiseptic # 1. Alcohols:

Alcohols, such as isopropanol and ethanol, probably are the most widely used antiseptics. Alcohols are used to reduce the numbers of microorganisms on the skin surface in the area of a wound, as well as for the disinfection of various contaminated objects. Alcohol denatures proteins, extracts membrane lipids, and acts as a dehydrating agent, all of which contribute to its effectiveness as an antiseptic. Even viruses are inactivated by alcohol.

Alcohol is far more effective than soap and water in reducing the numbers of microorganisms on the skin surface. On the skin, 70 percent ethanol kills nearly 90 percent of the cutaneous bacterial population within 2 minutes. Before puncturing the skin with a hypodermic syringe, the area is generally wiped with alcohol.

Oral thermometers also are often wiped with alcohol to kill disease-causing microorganisms that otherwise might be transmitted from one patient to another. Even though brief exposure to alcohol is not sufficient to achieve sterility, it does reduce the numbers of microorganisms to levels the make infection unlikely.

Antiseptic # 2. Iodine:

Iodine is a very effective antiseptic agent. It is bactericidal and sporicidal; that is, it kills all types of bacteria including endospores. It is also effective against many protozoa. Iodine is used in alcohol solution (tincture of iodine) and in combination with organic molecules (an iodophor).

Iodine combined with polymers such as polyvinylpyrolidone is a particularly effective antiseptic because the iodine is released slowly. Iodine is frequently applied to minor wounds to kill microorganisms on the skin, thereby preventing infection of the wound. Normally it does not seriously harm human tissues, but tincture of iodine stains tissue and may cause local skin irritation and occasional allergic reactions.

Iodophors are less irritating than tincture of iodine and do not stain the skin surface. Antiseptic iodophors are used routinely for preoperative skin cleansing and disinfection. In surgical procedures, the surgical staff often scrubs with soap impregnated with iodine, and the patient’s skin in the area of the incision is normally treated with iodine before beginning the surgical procedure.

Betadine and Isodine are frequently used for this purpose. A standard surgical scrub with a 10 percent solution (1 percent available iodine) decreases the cutaneous bacterial population by 85 percent and is particularly effective against any Gram negative bacteria that may be present.

Antiseptic # 3. Phenolics and Related Compounds:

Although phenol was perhaps the first antiseptic used to treat wounds, it is no longer used for this purpose because of its toxicity to human tissues. However, several phenolic compounds are widely used antiseptics. Resorcinol (meta-dihydroxybenzene) is only about one third as active as phenol, but it is both bactericidal and fungicidal.

Resorcinol is used in the treatment of acne, ringworm, eczema, psoriasis, dermatitis, and other cutaneous lesions. It is usually applied as a 10 percent ointment or lotion. Hexylresorcinol is commonly used in mouthwashes and in over-the-counter-drugs used for treating sore throats. Thymol is used in vaginal deodorants at a concentration of 1 percent because of its antibacterial and antifungal activities.

Hexachlorophene is one of the most useful of the phenol derivatives. Combined with a soap it is a highly effective skin disinfectant. Unlike most phenolic compounds, hexachlorophene has no irritating odor and has a high residual action. Hexachlorophene is more effective against Gram positive than against Gram negative bacteria.

A 3 percent solution of hexachlorophene will kill Staphylococcus within 30 seconds, but up to 24 hours may be required to kill Gram negative bacteria. Because most bacteria found on the skin are Gram positive, hexachlorophene once was commonly used by surgeons, physicians, and other health care workers. It was also used in the 1960s for daily bathing of newborns to prevent fatal Staphylococcus infections.

However, it was found that extended bathing of these infants could lead to neurological damage and therefore this practice was largely discontinued. Over-the-counter preparations of hexachlorophene were banned in the United States by the Food and Drug Administration, but it is still used for limited purposes in hospitals.

The use of pHisoHex as a surgical scrub has largely been replaced by the use of providone iodine (scrub soap form of betadine) and Hibiclens (chlorhexidine gluconate). These two scrubs are effective against a wide range of microorganisms commonly encountered in hospitals. The antimicrobial action of iodine has already been discussed.

Hibiclens is chemically different from other antimicrobials that are commonly used in the United States; chemically it is a biguanide. It maintains a high level of antimicrobial activity in the presence of organic matter, such as blood, and does not irritate or dry the skin.

Antiseptic # 4. Peroxides:

Hydrogen peroxide (H₂O₂) is an effective and nontoxic antiseptic. The molecule is unstable and degrades into water and oxygen. During the decomposition of peroxides a reactive form of oxygen-the superoxide radical-is formed, which is highly toxic to microorganisms. Anaerobic bacteria are particularly sensitive to peroxides. Hydrogen peroxide concentrations of 0.3 to 6.0 percent are used as antiseptics. A 3 percent solution is often used to cleanse and disinfect wounds.

Although its germicidal action is brief, the effectiveness of hydrogen peroxide against anaerobic bacteria is important because several deadly anaerobic bacteria often are associated with soils that may contaminate wounds. Higher concentrations of 6.0 to 25.0 percent can be used in sterilization. Such treatment is useful for surgical implants and contact lenses because it leaves no residual toxicity after a few minutes of exposure.

Antiseptic # 5. Dyes:

A variety of dyes that are bacteriostatic or bactericidal are widely used as antiseptics. For example, crystal violet, which is also called gentian violet, is a potent bacteriostatic agent for Gram positive bacteria and is bactericidal at concentrations of less than 1:10,000. The mechanism of action of this compound against Gram positive bacteria appears to be very similar to that of penicillin, blocking a final step in the synthesis of cell wall material.

Crystal violet has been used for the treatment of vaginal tract infections because both the protozoan Trichomonas and the fungus Candida albicans, two common etiologic agents of vaginitis, are very sensitive to this dye.

Antiseptic # 6. Heavy Metals:

Heavy metals are also used in antiseptic formulations. Mercury, zinc, and silver are examples of heavy metals used to kill microorganisms. The inhibitory effect of heavy metals is termed oligodynamic action.

Silver nitrate, for example, has classically been applied to the eyes of newborn human infants to kill possible microbial contaminants, in particular to prevent the transmission of gonococcal infections from mother to newborn. Silver combines with proteins and disrupts bacterial surface structures. Silver nitrate and silver sulfadizine are used to treat severe burns. Preventing infections of tissues exposed by burns is critical to the recovery of the patient.

Organic mercury compounds are effective antiseptics for the treatment of minor wounds and as preservatives in serums and vaccines. The organic mercurials are bacteriostatic and relatively nontoxic. Mercurachrome (merbromin) was the first organic mercurial antiseptic to be introduced. Actually mercurachrome has limited bacteriostatic action and the lowest therapeutic index of the commercial mercurial antiseptics. Metaphen and Merthiolate are more effective.

Salts of zinc are employed as mild antiseptics. Calamine lotion for example contains zinc oxide. Calamine lotion is used in the treatment of ringworm, impetigo, and various other cutaneous diseases. White lotion, which contains zinc sulfate at a concentration of 4 percent, is also used to treat skin diseases and infections.

A mixture of a long chain fatty acid and the zinc salt of the acid is commonly used as an antifungal powder or ointment. It is particularly effective in the treatment of athlete’s foot. The zinc salt also acts as an astringent and aids in healing superficial lesions, as does zinc oxide paste, which is commonly recommended for treating diaper rash and its concurrent bacterial or fungal infections.

Antiseptic # 7. Quaternary Ammonium Compounds:

Several quaternary ammonium cationic detergents are used as antiseptic agents. These compounds are relatively non-irritating to human tissues at concentrations that are inhibitory to microorganisms. However, they act slowly and are inactivated by soaps.

They are also adsorbed by cotton and other porous materials, which can severely interfere with their effectiveness as antiseptics. Zephiran, Phemerol, Cepacol and Bradosol are examples of quats that are used as antiseptics. Cepacol and Bradosol, for example, are used in throat lozenges.

Antiseptic # 8. Acids:

Several acids are used as antiseptics. Acetic acid at a concentration of 5 percent is bactericidal and at lower concentrations is bacteriostatic. It is occasionally used at a concentration of 1 percent in surgical dressings. Pseudomonas aeruginosa is particularly susceptible to acetic acid, and this acid may be employed in burn therapy. It is used in vaginal douches and to suppress fungal and protozoan infections of the vaginal tract.

Undecylenic acid is active against a variety of fungi, including the fungi that cause superficial mycoses. It is usually compounded with zinc but may also be used alone. Compound undecylenic acid contains 2-5 percent undecylenic acid and 20 percent zinc undecylenate. This antiseptic agent is very useful for the treatment of ringworm.

Undecylenic acid is the active ingredient in Desenex, which is used to treat athelete’s foot and other fungus infections of the skin. Benzoic acid and salicylic acid used in combination also inhibit fungal growth. Whitfield’s ointment contains benzoic acid and salicylic acid in a ratio of 2:1. This ointment is used to prevent fungal growth on the feet as occurs in athlete’s foot.