Antisepsis - The search for antiseptics
Antisepsis is the prevention or inhibition of an infection by either killing the organism responsible for the infection, or weakening the organism so that it is unable to cause the infection or survive. This is usually achieved by application of an antiseptic or germicidal preparation.
An antiseptic differs from an antibiotic. An antibiotic is specifically directed to a target bacterium or different types of bacteria. There are many different classes of antibiotics, some of which can kill only a few types of bacteria; others are effective against many types of bacteria.
An antiseptic is a chemical compound that is "broad spectrum" in its activity; that is, it kills a wide variety of bacteria and other microorganisms. Because many antiseptics are used on the skin (e.g., "swabbing" the skin with iodine before an injection), antiseptics tend to be non-irritating.
The search for antiseptics
The search for antiseptic agents is as old as humanity. In a hieroglyphic prescription dating from c. 1500 B.C., an Egyptian is depicted ordering a mixture of grease and honey for treatment of a wound. While infections and their causes were not known at that time, the relief provided by antiseptic compounds was recognized.
Other historical "cures" for infections include plant extracts, broths of animal or plant materials, and poultices of moss, mud, or dung, Not until the eighteenth century did progress begin to be made toward conquering everyday infections.
As late as the beginning of the nineteenth century, physicians had no knowledge of the septic (infectious) process or its prevention. Although surgery had developed steadily, the mortality rate among patients was high. Whether the patient would die from an infected organ or from the surgery to remove it often was a moot point. Surgeons went from one patient to the next without washing their hands or changing aprons. Thus, the bacteria from one patient were readily passed to the next and sepsis was an accepted fact.
In the middle of the nineteenth century, the Hungarian obstetrician Ignaz Semmelweiss (1818–1865) proposed that the infectious agent of puerperal fever, which was fatal to many women during childbirth (hence its other name, childbed fever), could be spread by the attending physician. Semmelweiss further suggested that washing hands between patients could prevent the infection. At first he was ridiculed, but when his rate of fatal puerperal fever infections declined rapidly with his practice of washing his hands, other obstetricians soon adopted the practice. This was the first introduction of antisepsis into medical practice.
In the latter half of the nineteenth century, British physician Joseph Lister (1827–1912) introduced the practice of spraying carbolic acid over patients during operations. This reduced the contamination of the open wound from airborne microorganisms and microbes on the doctor's clothing or gloves. Lister's innovation brought aseptic technique into the operating theatre.
The early antiseptics were based on mercury (mercurochrome, merthiolate), but have fallen into disuse. Although mercury poses a serious health hazard if absorbed into the body, the small amounts of mercury in the mercury-based antiseptics posed little threat. They were discontinued because they were relatively ineffective. Although mercury-based antiseptics readily stopped bacteria from reproducing and spreading, they did not kill the microorganism. Once the merthiolate was washed away, the bacteria revived and resumed their invasion of the tissues.
Now, the innovations of Semmelweiss and Lister are an accepted part of medicine. Modern antisepsis is both preventive and therapeutic. Examples of preventive measures include hand washing by the surgeon, use of sterile surgical gowns, masks, gloves and equipment, and the preparation of the patient's skin with antiseptic. Therapeutic antisepsis is the application of a bactericidal agent to an infected area to kill the infectious agent.
Antiseptics have also found their way into the home. Various powders, liquids, or ointments are applied to the surface of the skin to prevent infection of a cut, splinter, or other superficial wound. These antiseptics are for external use only and each is effective against only one type of bacterium (e.g., gram positive bacteria).
Newer antiseptics are based on the quaternary ammonium compounds (such as benzalkonium chloride and benzethonium chloride). "Quats" are longstanding and powerful antiseptics. Other common antiseptics include alcohols (e.g., ethyl or isopropyl alcohol), hydrogen peroxide, and phenol. Each is effective against a narrow range of bacterial infections, but none is effective against viruses. These antiseptics often are mixed to provide a wider range of antibacterial activity. They are applied externally on a cut or scrape to prevent infection and, when incorporated into mouthwash, can be gargled to kill bacteria that may cause a sore throat.
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