Disinfectants and Antiseptics: Types, Properties, and Classification - Prof. Noor, Slides of Pharmaceutical Microbiology

Download Disinfectants and Antiseptics: Types, Properties, and Classification - Prof. Noor and more Slides Pharmaceutical Microbiology in PDF only on Docsity! Disinfectants and antiseptics Pharm 229B By Humaira Binte Noor Lecturer University of Asia Pacific Germicide: the chemical used for the purpose of non-selective killing or inhibiting growth of microbes (bacteria, virus, fungi and protozoa) on contact are called germicide. Germicides are of two types: a. Antiseptic- are the germicide applied on living surface . b. Disinfectant- are usually applied to the surface of inanimate objects and eliminate all pathogenic microorganisms excluding spores. An ideal disinfectant or antiseptic should have the following properties: • It should be able to kill all kinds of microbes in a very diluted form and relatively short time. • Its efficacy should not be reduced in presence of blood, feces or other organic matters. • It should be non- toxic to animals or humans, non-staining and non- offensive. • It should be soluble in water and have a reasonable shelf -life. • It should have good wetting and penetrating properties (i.e., it should be a good surface tension reducer). • It should not separate on standing, should penetrate well and should not corrode instruments. • Finally, it should be cheap and easily available. Types of disinfection • Concurrent disinfection is carried out during the course of patient's illness. • Terminal disinfection is disinfection of infected material after removal of patient to hospital, after recovery or death. • Prophylactic disinfection includes the processes of pasteurization of milk and water purification by chlorination etc. Classification of disinfectants • Natural: air and sun light prevent the growth of microorganisms. • Physical: dry heat, moist heat, and radiations. • Chemical: solid, liquid and gaseous. • Halogen is believed to cause the release of atomic oxygen, which combines with and inactivates certain cytoplasmic enzymes in microorganisms. • According to another theory chlorine changes the structure of cell membranes thus leading to leakage. • Chlorine and iodine are the two amongst halogens that are used in disinfection. • Chlorine is available in organic, inorganic and gaseous forms mainly employed to keep bacterial population at low levels in municipal water supply. It combines readily with numerous ions in water and the residue of chlorine is usually about 0.2 to 1.0 ppm. • Chlorine is effective against a variety of organisms including most gram- positive, Gram-negative bacteria, many viruses, fungi, and protozoa, but it is not sporicidal. Halogens • Iodine is more reactive and more germicidal. It acts by halogenating tyrosine portions of protein molecules. • Tincture iodine is commonly used antiseptic for wounds. Iodine compounds are also valuable sanitizers for restaurant eating utensils and equipment. • Iodophors (iodine-detergent complexes) is used to eliminate the side effects of iodine while retaining its antimicrobial activity. Iodophors (iodo meaning iodine and phor meaning carrier) may also be combined with non-detergent carrier molecules e.g. povidone, which stabilizes the iodine and releases it slowly. • In addition to chlorine and iodine, the elements and compounds of bromine and fluorine are also useful disinfectants, but they are too toxic at the effective concentrations to be used as antiseptics. Phenols and Phenolic Compounds • The disinfectants of phenolics family are rapidly bactericidal, but their activity is markedly diminished by dilution and is also reduced by organic matter. Phenol and its derivative are active against cytoplasmic membrane of bacteria. They denature protein and act as cytoplasmic poison. In viruses they damage viral lipid. • The main disadvantages of phenols are their caustic effect on skin and tissues and their systemic toxicity. • Phenol (carbolic acid) is expensive, has pungent odor, and is caustic to the skin. It is believed that phenol and its derivatives act by coagulating proteins, especially in cell membrane. • Substituted phenol obtained by introducing various chemical groups into phenol nucleus possess bactericidal activity e.g. cresols (methyl phenols), xylenols (dimethyl phenols) and the chloroxylenols. Heavy Metals • Greeks and Romans used mercury as mercuric chloride (HgCl2) as antiseptic for treating skin diseases. Mercuric chloride and oxycyanide are very toxic and inactivated by organic matter. They are largely bacteriostatic, and their bactericidal activity is negligible under most conditions. • In certain organic compounds such as thiomersal, mercurochrome, merthiolate and metaphen, mercury is combined with carrier compounds and is less toxic, but they too have very slight bactericidal activity. • Copper is a potent inhibitor of algae and hence copper sulphate is incorporated in algaecides. • Silver in the form of silver nitrate and silver sulphadiazine cream is used in the treatment of burns, Silver nitrate is useful as disinfectant not antiseptic. Alcohols • The aliphatic alcohols e.g. ethanol and isopropanol used for disinfection are bactericidal against vegetative forms but are not sporicidal. • Ethyl alcohol kills vegetative bacteria, including Mycobacterium tuberculosis and some viruses fairly rapidly if used at a concentration of about 70%. It has poor penetrating power and is not much useful in the presence of such organic matter. • lt denatures proteins and dissolves lipids, which may lead to disinfection of cell membrane. Pure ethanol has no antibacterial activity. Ethyl alcohol is used for preparing the skin prior to injections and disinfection of trolley tops and other clear surfaces in high-risk areas. • Isopropyl alcohol or rubbing alcohol has greater activity. At a concentration of 70%, it is used for disinfecting the skin, thermometers, trolley tops and other work surfaces. Aldehyde- Formaldehyde • Formaldehyde a solid at room temperature and gas at high temperature. This irritant gas is effective against bacteria(including M. tuberculosis), fungi, viruses and more slowly spores. • Formalin is a 37% aqueous solution of formaldehyde used for incorporating viruses in certain vaccines and producing toxoids from toxins. Dilute solutions kill motile bacteria but preserve their H antigen. • Formaldehyde in combination with low temperature steam, can be used to sterilize surgical equipment. Formaldehyde is the most satisfactory agent for disinfecting clothing, blankets, pillows, mattresses, toys and similar articles but the process is not reliable. • Formaldehyde kills microorganisms through its action as alkylating agent, on amino and hydroxyl groups of nucleic acids and proteins, and with carboxyl and sulphydryl groups in proteins. Potassium permanganate (KMnO4) • It is popular in tropics for disinfecting drinking water, fruits and vegetables. Ozone • It is a powerful germicidal agent, but it is highly toxic, too expensive and inconvenient for routine use. It can be used for disinfecting water and for preserving food. Soaps and detergents • Soaps cause microbial destruction due to the alkaline conditions and act as degerming agent for the mechanical removal of microorganisms from the skin surface. • Anionic detergents have little germicidal activity but can be used in combination with phenolic disinfectants in operating theatres and other high-risk areas. • Cationic detergents e.g. cetrimide (cetyl tri methyl ammonium bromide) are bacteriostatic on a broad range of bacteria, spores and viruses are highly resistant. Their ability is reduced in presence of organic matter. They are useful for disinfection of hospital walls and floors as sanitizing agents, mouthwashes and storage solution for contact lenses. • Nonionic detergents such as ethylene oxide condensates, have almost no germicidal activity but they are excellent cleansing agents and can be used in conjunction with many disinfectants • Dyes: Triphenylmethane dyes e.g. crystal violet and malachite green are useful as antiseptics against species of Bacillus and Staphylococcus. Crystal violet is bactericidal at very weak dilute solution of less than 0.01%. • Acids: Certain acids e.g. benzoic, salicylic acids are useful as antiseptics and disinfectants. Vinegar (acetic acid), benzoic acid and lactic acid are used for preserving foods. Propionic acid is added to bakery products to minimize microbial population. • Nitrofurazone: A nitrofuran derivative is bacteriocidal to both gram positive and gram negative, aerobic and anaerobic bacteria. It acts by inhibiting enzyme of carbohydrate metabolism in bacteria. It is highly efficacious topically as 0.2% cream in burns and skin infections. • Surface tension: The contact between aqueous solutions of disinfectants is facilitated if they have surfactant properties. This helps in adsorption of surfactant disinfectants on the surfaces of cells as well as in wetting and spreading properties of the solutions. Thank You