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SNC4M Pathogens and Disease Unit An introduction to disinfectants, antiseptics and antibiotics Disinfectants and antiseptics do the same thing – they kill bacteria very rapidly on contact. A distinction between the two types of agent is made because disinfectants generally kill bacteria on surfaces, floors and non-living objects whereas antiseptics are used to kill bacteria on the skin of people or animals. Neither should be confused with antibiotics, drugs that are given to people or animals to kill bacteria inside the body. Disinfectants A wide range of different substances are used as disinfectants, including alcohols (also used as antiseptics), aldehydes, such as ortho-phthalaldehyde, bleaches based on chlorine compounds, hydrogen peroxide and also iodine (also another traditional antiseptic) and potassium permanganate solution. Phenolic compounds also have anti-bacterial activity and are often used in disinfectants bought for use in the home, and in disinfectant hand-washes and soaps. Different disinfectants work in different ways. Hydrogen peroxide, which reacts to produce free oxygen radicals and bleaches that are based on chlorine compounds are very powerful oxidising agents. They oxidise the complex molecules present on the surface of bacteria, causing their cell walls and cell membranes to disrupt. The proteins on the surface become irreversibly damaged and start to stick together forming clumps. This happens very quickly – a strong solution of sodium hypochlorite solution that is used to disinfect a toilet, for example, kills bacteria within seconds. The bacterial cell cannot respond to the damage quickly enough and the whole cell simply splits open and dies. Recent research has shown that bacteria do have some capacity to resist an attack by bleach. Contact with hypochlorous acid was found to switch on a gene in some bacteria that is part of the pathway that bugs use to cope with heat stress and bleach-like substances that cells of the immune system produce to fight off infection. If the concentration of bleach solution is low, bacteria with genes that resist this sort of cellular attack might be able to survive cleaning. Antiseptics Antiseptics are placed on the skin, usually in an area where the skin has been damaged, such as a cut or a graze. They are also used to clean the skin before intentional cuts are made in surgical operations. Those that kill bacteria outright are described as bactericidal. Other antiseptics, described as bacteriostatic, stop bacteria from growing or dividing, but do not kill them. Common antiseptics used during the last 150 years or so include alcohol, boric acid, hydrogen peroxide, iodine, carbolic acid and other phenol compounds, chlorohexadine, sodium chloride, sodium hypochlorite and calcium hypochlorite. The latter is also known as chlorinated lime and was used by Ignaz Semmelweis in the 1840s when he tried to prevent puerperal fever spreading in a maternity ward in Vienna. SNC4M Pathogens and Disease Unit The widespread use of antiseptics did not really begin until the 1870s, due mainly to the work and publications of the English surgeon Joseph Lister. The link between bacteria and disease was made around that time and Lister pioneered the use of antiseptics before, during and after surgery, which was also a new technique at the time. Modern Use Disinfectants and antiseptics are now used extensively in hospitals and other medical treatment centres, where they help to maintain a clean environment that can prevent the spread of bacteria from person to person. Disinfectants and antiseptics used properly are still able to kill bacterial strains that have become resistant to antibiotic treatment. In the last 20 years, the use of disinfectants such as anti-bacterial sprays has increased in the home but this may not necessarily be a good thing. The vast majority of bacteria in our home environment are friendly bacteria and do not cause disease. Using anti-bacterial products all over the home is probably unnecessary. Cleaning danger areas such as toilets, drains and rubbish bins with a suitable disinfectant or bleach solution is very likely to be sufficient. Antibiotics Introduction The word antibiotic comes from the Greek anti meaning 'against' and bios meaning 'life' (a bacterium is a life form).' Antibiotics are also known as antibacterials, and they are drugs used to treat infections caused by bacteria. Bacteria are tiny organisms that can sometimes cause illness to humans and animals. The singular word for bacteria is bacterium. Such illnesses as tuberculosis, salmonella, syphilis and some forms of meningitis are caused by bacteria. Some bacteria are not harmful, while others are good for us. Before bacteria can multiply and cause symptoms our immune system can usually destroy them. We have special white blood cells that attack harmful bacteria. Even if symptoms do occur, our immune system can usually cope and fight off the infection. There are occasions, however, when it is all too much and our bodies need some help - from antibiotics. The first antibiotic was penicillin. Such penicillin-related antibiotics as ampicillin, amoxicillin and benzylpenicilllin are widely used today to treat a variety of infections - these antibiotics have been around for a long time. There are several different types of modern antibiotics and they are only available with a doctor's prescription in industrialized countries. SNC4M Pathogens and Disease Unit How do antibiotics work? Although there are a number of different types of antibiotic they all work in one of two ways: A bactericidal antibiotic kills the bacteria. Penicillin is a bactericidal. A bactericidal usually either interferes with the formation of the bacterium's cell wall or its cell contents. A bacteriostatic stops bacteria from multiplying. What are antibiotics for? An antibiotic is given for the treatment of an infection caused by bacteria. Antibiotics target microorganisms such as bacteria, fungi and parasites. However, they are not effective against viruses because viruses are not microorganisms. If you have an infection it is important to know whether it is caused by bacteria or a virus. Most upper respiratory tract infections, such as the common cold and sore throats are generally caused by viruses - antibiotics do not work against these viruses. If antibiotics are overused or used incorrectly there is a chance that the bacteria will become resistant - the antibiotic becomes less effective against that type of bacterium. A broad-spectrum antibiotic can be used to treat a wide range of infections. A narrow-spectrum antibiotic is only effective against a few types of bacteria. There are antibiotics that attack aerobic bacteria, while others work against anaerobic bacteria. Aerobic bacteria need oxygen, while anaerobic bacteria don't. Antibiotics are among the most frequently prescribed medications in modern medicine. Antibiotics cure disease by killing or injuring bacteria. The first antibiotic was penicillin, discovered accidentally from a mold culture. Today, over 100 different antibiotics are available to doctors to cure minor discomforts as well as life-threatening infections. Although antibiotics are useful in a wide variety of infections, it is important to realize that antibiotics only treat bacterial infections. Antibiotics are useless against viral infections (for example, the common cold) and fungal infections (such as ringworm). Your doctor can best determine if an antibiotic is right for your condition.