Antiseptics and Disinfectants

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Transcript of Antiseptics and Disinfectants

INTRODUCTONAntiseptics and disinfectants are used extensively in hospitals and other health care settings for a variety of topical and hard-surface applications. In particular, they are an essential part of infection control practices and aid in the prevention of nosocomial infections (1). Mounting concerns over the potential for microbial contamination and infection risks in the food and general consumer markets have also led to increased use of antiseptics and disinfectants by the general public. A wide variety of active chemical agents (or biocides) are found in these products, many of which have been used for hundreds of years for antisepsis, disinfection, and preservation (2).

DEFINITIONSBiocide is a general term describing a chemical agent, usually broad spectrum that inactivates microorganisms. Antibiotics are defined as naturally occurring orsynthetic organic substances which inhibit or destroy selective bacteria or other microorganisms, generally at low concentrations. -In general, biocides have a broader spectrum of activity than antibiotics, and, while antibiotics tend to have specific intracellular targets, biocides may have multiple targets.

Disinfectants are products or biocides that are used on inanimate objects orsurfaces such as in hospitals, clinics, homes and schools. They are used to clean surfaces such as toilets, floors, drains, door knobs and garbage cans. Disinfectants aid in maintaining a clean environment to help prevent the spread of harmful bacteria that may cause infections.

Antiseptics are applied to the skin either to sterilize a cut or used for handwashing such as before a surgical procedure or contact with those who are at a high risk of infection such as newborn babies. Antiseptics destroy and inhibit the growth of microorganisms on the skin or mucous membranes. They are not as strong as disinfectants, so they shouldn't be used to clean objects and surfaces (3).

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Although biocides are important chemicals used for a variety of purposes such as killing different types of germs which may cause all kinds of diseases. They may be hazardous waste, irritants and can be harmful to humans, particularly in strong concentrations. Some disinfectants are used to kill crop bacteria and other microorganisms. Some of these disinfectants are capable of causing danger to humans. There is an ongoing controversy over using some disinfectants on crops. Glutaraldehyde is used to kill microorganisms on crops and vegetables. Stronger (4) concentrations could be harmful to humans .

An ideal antiseptic or disinfectant should have following properties: Should have wide spectrum of activity. Should be able to destroy microbes within practical period of time. Should be active in the presence of organic matter. Should make effective contact and be wettable. Should be active in any pH. Should be stable. Should have long shelf life. Should be speedy. Should have high penetrating power. Should be non-toxic, non-allergenic, non-irritative or non-corrosive. Should not have bad odour. Should not leave non-volatile residue or stain. Should not be expensive and must be available easily. Controlling biofilms.

Such an ideal disinfectant is not yet available. The level of disinfection achieved depends on contact time, temperature, type and concentration of the active ingredient, the presence of organic matter, the type and quantum of microbial load. The chemical disinfectants at working concentrations rapidly lose their strength on standing (5).

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Mechanisms of antibacterial action of antiseptics and disinfectants according to target side:A- Cell wall (Membrane active agent).1Glutaraldehyde (CH2CHO)2 is an important dialdehyde that has found usage as a disinfectant and sterilant, in particular for low-temperature disinfection and sterilization of endoscopes and surgical equipment and as a fixative in electron microscope. Glutaraldehyde has a broad spectrum of activity against bacteria and their spores, fungi, and viruses (6). - Glutaraldehyde is strongly binding to outer layers of organisms, specifically with unprotonated amines on the cell surface such as E. coli and Staphylococcus aureus. It inhibits dehydrogenase activity and periplasmic enzymes and inhibits spheroplast and protoplast lysis in hypotonic media. It forms protein-DNA crosslinks and inhibit RNA, DNA, and protein synthesis (7, 8).

Mechanism of antimicrobial action of GlutaraldehydeTarget microorganism Bacterial spores Glutaraldehyde action Low concentrations inhibit germination; High concentrations are sporicidal, probably as a consequence of strong interaction with outer cell layers. Action unknown, but probably involves mycobacterial cell wall. Strong association with outer layers of grampositive and gram-negative bacteria; crosslinking of amino groups in protein; inhibition of transport processes into cell. Fungal cell wall appears to be a primary target site, with postulated interaction with chitin. Actual mechanisms unknown, but involve protein-DNA cross-links and capsid changes.Page | 3


Other non-sporulating bacteria

Fungi Viruses

2Formaldehyde (methanal, CH2O) is a monoaldehyde that exists as a freely water-soluble gas. Its clinical use is generally as a disinfectant and sterilant in liquid or in combination with low-temperature steam. Formaldehyde is bactericidal, sporicidal, and virucidal, but it works more slowly than glutaraldehyde (7, 8). Formaldehyde is an extremely reactive chemical that interacts with protein, DNA, and RNA in vitro. It has long been considered to be sporicidal by virtue of its ability to penetrate into the interior of bacterial spores. The interaction with protein results from a combination with the primary amide as well as with the amino groups. Formaldehyde also reacts extensively with nucleic acid (e.g., the DNA of bacteriophage T2). It forms protein-DNA cross-links in SV40 (Simian Vacuolating Virus 40 T-Ag) , thereby inhibiting DNA synthesis. Low concentrations of formaldehyde are sporostatic and inhibit germination.

B- Cytoplasmic (inner) membrane.1Chlorhexidine probably the most widely used biocide in antiseptic products (e.g. Cyteal*), in particular in handwashing and oral products (e.g. EZ-care*) but also as a disinfectant and preservative. This is due in particular to its broadspectrum efficacy, persistence on the skin, and low irritation. Despite the advantages of chlorhexidine, its activity is pH dependent and is greatly reduced in the presence of organic matter (9). Chlorhexidine is a bactericidal agent. Its interaction and uptake by bacteria were studied initially by Hugo et al., who found that the uptake of chlorhexidine by E. coli and S. aureus was very rapid and depended on the chlorhexidine concentration (10). -At low concentration, Chlorhexidine damaged to the outer cell layers takes place; the agent then crosses the cell wall or outer membrane by passive diffusion, and attacks the bacterial cytoplasmic or inner membrane or the yeast plasma membrane. Damage to the delicate semipermeable membrane is followed by leakage of intracellular constituents and then cell death (11).Page | 4

-High concentrations of chlorhexidine cause coagulation of intracellular constituents. As a result, the cytoplasm becomes congealed, with a consequent reduction in leakage, so there is a biphasic effect on membrane permeability (12).

Mechanism of antimicrobial action of ChlorhexidineType of microorganism Bacterial spores Mycobacteria Other non-sporulating bacteria Chlorhexidine action Not sporicidal but prevents development of spores. Inhibits spore outgrowth but not germination (the emergence of cells from resting spores). Mycobacteristatic but not mycobactericidal. Membrane-active agent, causing protoplast and spheroplast lyses. High concentrations cause precipitation of proteins and nucleic acids Membrane-active agent, causing protoplast lysis and intracellular leakage; high concentrations cause intracellular coagulation. Low activity against many viruses; lipidenveloped viruses more sensitive than nonenveloped viruses (Rota and polio viruses); effect possibly on viral envelope, perhaps the lipid moieties.



2- The diamidines salts of two compounds, propamidine and dibromopropamidine have been used as antibacterial agents. They are used for the topical treatment of wounds (13). The exact mechanism of action of diamidines is unknown, but they have been shown to inhibit oxygen uptake, generalized membrane damage and induce leakage of amino acids (14).Page | 5

3The cationic surfactant agents, as exemplified by quaternary ammonium compounds (QACs), are the most useful antiseptics and disinfectants. They are sometimes known as cationic detergents. QACs have been used for a variety of clinical purposes (e.g., preoperative disinfection of unbroken skin- Salvon* and application to mucous membranes). In addition to having antimicrobial properties and used as eye drop preservative. QACs are also excellent for hard-surface cleaning and deodorization (15). They are not corrosive except at high concentrations cause skin burn; they are stable even in diluted solutions and concentrates, can be stored for a long time without losing their antimicrobial activity(15). Salton proposed the following sequence of events with microorganisms exposed to cationic agents: (i) Adsorption and penetration of the agent into the cell wall. (ii) Reaction with the cytoplasmic membrane (lipid or protein) followed by membrane disorganization (iii) Leakage of intracellular low-molecular-weight material. (iv) Degradation of proteins and nucleic acids. There is thus a loss of structural organization and integrity of the cytoplasmic membrane in bacteria (16). QACs are sporostatic; they inhibit the outgrowth of spores (the development of a veg