, who was awarded the Nobel Prize in Medicine for developing 22 antibiotics—most notably
Streptomycin Antibacterials Antibacterials are used to treat
bacterial infections. Antibiotics are classified generally as
beta-lactams,
macrolides,
quinolones,
tetracyclines or
aminoglycosides. Their classification within these categories depends on their antimicrobial spectra, pharmacodynamics and chemical composition. Prolonged use of certain antibacterials can decrease the number of
enteric bacteria, which may have a negative impact on
health. Consumption of
probiotics and healthy eating may help to replace destroyed gut
flora.
Stool transplants may be considered however for patients who are having difficulty recovering from prolonged antibiotic treatment, such as recurrent
Clostridioides difficile infections. The discovery, development and use of antibacterials during the 20th century have reduced mortality from bacterial infections. The antibiotic era began with the therapeutic application of sulfonamide drugs in 1936, followed by a "golden" period of discovery from about 1945 to 1970, when a number of structurally diverse and highly effective agents were discovered and developed. Since 1980, the introduction of new antimicrobial agents for clinical use has declined, in part because of the enormous expense of developing and testing new drugs. In parallel, there has been an alarming increase in
antimicrobial resistance of bacteria, fungi, parasites and some viruses to multiple existing agents. Antibacterials are among the most commonly used and misused drugs by physicians, for example, in viral
respiratory tract infections. As a consequence of widespread and injudicious use of antibacterials, there has been an accelerated emergence of antibiotic-resistant pathogens, resulting in a serious threat to global public health. The resistance problem demands that a renewed effort be made to seek antibacterial agents effective against pathogenic bacteria resistant to current antibacterials. Possible strategies towards this objective include increased sampling from diverse environments and application of
metagenomics to identify bioactive compounds produced by currently unknown and uncultured microorganisms as well as the development of small-molecule libraries customized for bacterial targets.
Antifungals Antifungals are used to kill or prevent further growth of
fungi. In medicine, they are used as a treatment for infections such as
athlete's foot,
ringworm and
thrush and work by exploiting differences between mammalian and fungal cells. Unlike bacteria, both fungi and humans are
eukaryotes. Thus, fungal and human
cells are similar at the molecular level, making it more difficult to find a target for an antifungal drug to attack that does not also exist in the host organism. Consequently, there are often
side effects to some of these drugs. Some of these side effects can be life-threatening if the drug is not used properly. As well as their use in medicine, antifungals are frequently sought after to control
indoor mold in damp or wet home materials.
Sodium bicarbonate (baking soda) blasted on to surfaces acts as an antifungal. Another antifungal solution applied after or without blasting by soda is a mix of
hydrogen peroxide and a thin surface coating that neutralizes mold and encapsulates the surface to prevent spore release. Some paints are also manufactured with an added antifungal agent for use in high humidity areas such as bathrooms or kitchens. Other antifungal surface treatments typically contain variants of metals known to suppress mold growth e.g. pigments or solutions containing
copper,
silver or
zinc. These solutions are not usually available to the general public because of their toxicity.
Antivirals Antiviral drugs are a class of medication used specifically for treating
viral infections. Like antibiotics, specific antivirals are used for specific viruses. They should be distinguished from
viricides, which actively deactivate virus particles outside the body. Many antiviral drugs are designed to treat infections by
retroviruses, including
HIV. Important
antiretroviral drugs include the class of
protease inhibitors.
Herpes viruses, best known for causing
cold sores and
genital herpes, are usually treated with the
nucleoside analogue acyclovir.
Viral hepatitis is caused by five unrelated hepatotropic viruses (A-E) and may be treated with antiviral drugs depending on the type of infection. Some
influenza A and
B viruses have become resistant to
neuraminidase inhibitors such as
oseltamivir, and the search for new substances continues.
Antiparasitics Antiparasitics are a class of medications indicated for the treatment of infectious diseases such as
leishmaniasis,
malaria and
Chagas disease, which are caused by
parasites such as
nematodes,
cestodes,
trematodes and infectious
protozoa. Antiparasitic medications include
metronidazole,
iodoquinol and
albendazole.
Broad-spectrum therapeutics Broad-spectrum therapeutics are active against multiple classes of pathogens. Such therapeutics have been suggested as potential emergency treatments for
pandemics.
Non-pharmaceutical A wide range of chemical and natural compounds are used as antimicrobials.
Organic acids and their salts are used widely in food products, e.g.
lactic acid,
citric acid,
acetic acid, either as ingredients or as disinfectants. For example, beef carcasses often are sprayed with acids, and then rinsed or steamed, to reduce the prevalence of
Escherichia coli. Heavy metal cations such as
Hg2+ and
Pb2+ have antimicrobial activities, but can be toxic. In recent years, the antimicrobial activity of coordination compounds has been investigated. Traditional herbalists used plants to treat infectious disease. Many of these plants have been investigated scientifically for antimicrobial activity, and some plant products have been shown to inhibit the growth of pathogenic microorganisms. A number of these agents appear to have structures and modes of action that are distinct from those of the antibiotics in current use, suggesting that
cross-resistance with agents already in use may be minimal.
Copper Copper-alloy surfaces have natural intrinsic antimicrobial properties and can kill microorganisms such as
E. coli and
Staphylococcus. The
United States Environmental Protection Agency approved the registration of
antimicrobial copper alloy surfaces for use in addition to regular cleaning and disinfection to control infections. Antimicrobial copper alloys are being installed in some healthcare facilities and subway transit systems as a public hygienic measure.
Essential oils Many
essential oils included in
herbal pharmacopoeias are claimed to possess antimicrobial activity in vitro, with the oils of
bay,
cinnamon,
clove and
thyme reported to be the most potent in studies with
foodborne bacterial pathogens. While 25 to 50% of pharmaceutical compounds are plant-derived, none are used as antimicrobials, though there has been increased research in this direction. Barriers to increased usage in mainstream medicine include poor regulatory oversight and quality control, evidence only from in vitro studies, mislabeled or misidentified products, and limited modes of delivery.
Antimicrobial pesticides According to the
U.S. Environmental Protection Agency (EPA), and defined by the
Federal Insecticide, Fungicide, and Rodenticide Act, antimicrobial pesticides are used to control growth of microbes through disinfection, sanitation, or reduction of development and to protect inanimate objects, industrial processes or systems, surfaces, water, or other chemical substances from contamination, fouling, or deterioration caused by bacteria, viruses, fungi, protozoa, algae, or slime. The EPA monitors products, such as disinfectants/sanitizers for use in hospitals or homes, to ascertain efficacy. Products that are meant for public health are therefore under this monitoring system, including products used for drinking water, swimming pools, food sanitation, and other environmental surfaces. These pesticide products are registered under the premise that, when used properly, they do not demonstrate unreasonable side effects to humans or the environment. Even once certain products are on the market, the EPA continues to monitor and evaluate them to make sure they maintain efficacy in protecting public health. Public health products regulated by the EPA are divided into three categories: Organizations such as the
World Health Organization call for significant reduction in their use globally to combat this. According to a 2010
Centers for Disease Control and Prevention report, health-care workers can take steps to improve their safety measures against antimicrobial pesticide exposure. Workers are advised to minimize exposure to these agents by wearing
personal protective equipment such as gloves and safety glasses. Additionally, it is important to follow the handling instructions properly, as that is how the EPA has deemed them as safe to use. Employees should be educated about the health hazards and encouraged to seek medical care if exposure occurs.
Ozone Ozone can kill microorganisms in air, water and process equipment and has been used in settings such as kitchen exhaust ventilation, garbage rooms, grease traps,
biogas plants,
wastewater treatment plants, textile production,
breweries,
dairies, food and hygiene production,
pharmaceutical industries, bottling plants, zoos, municipal drinking-water systems,
swimming pools and spas, and in the laundering of clothes and treatment of in–house mold and odors.
Antimicrobial scrubs Antimicrobial
scrubs can reduce the accumulation of odors and stains on scrubs, which in turn improves their longevity. These scrubs also come in a variety of colors and styles. As antimicrobial technology develops at a rapid pace, these scrubs are readily available, with more advanced versions hitting the market every year. These bacteria could then be spread to office desks, break rooms, computers, and other shared technology. This can lead to outbreaks and infections like
methicillin-resistant staphylococcus aureus, treatments for which cost the healthcare industry $20 billion a year.
Halogens Elements such as chlorine, iodine, fluorine, and bromine are nonmetallic in nature and constitute the
halogen family. Each of these halogens have a different antimicrobial effect that is influenced by various factors such as pH, temperature, contact time, and type of microorganism. Chlorine and iodine are the two most commonly used antimicrobials. Chlorine is extensively used as a disinfectant in the water treatment plants, drug, and food industries. In wastewater treatment plants, chlorine is widely used as a disinfectant. It oxidizes soluble contaminants and kills bacteria and viruses. It is also highly effective against bacterial spores. The mode of action is by breaking the bonds present in these microorganisms. When a bacterial enzyme comes in contact with a compound containing chlorine, the hydrogen atom in that molecule gets displaced and is replaced with chlorine. This in turn changes the enzyme function which ultimately leads to the death of the bacterium. Iodine is most commonly used for sterilization and wound cleaning. The three major antimicrobial compounds containing iodine are alcohol-iodine solution, an aqueous solution of iodine, and iodophors. Iodophors are more bactericidal and are used as antiseptics as they are less irritating when applied to the skin. Bacterial spores on the other hand cannot be killed by iodine, but they can be inhibited by iodophors. The growth of microorganisms is inhibited when iodine penetrates into the cells and oxidizes proteins, genetic material, and fatty acids. Bromine is also an effective antimicrobial that is used in water treatment plants. When mixed with chlorine it is highly effective against bacterial spores such as
S. faecalis. Alcohols Alcohols are commonly used as disinfectants and antiseptics. Alcohols kill vegetative bacteria, most viruses and fungi. Ethyl alcohol, n-propanol and isopropyl alcohol are the most commonly used antimicrobial agents. Methanol is also a disinfecting agent but is not generally used as it is highly poisonous.
Escherichia coli,
Salmonella, and
Staphylococcus aureus are a few bacteria whose growth can be inhibited by alcohols. Alcohols have a high efficiency against enveloped viruses (60–70% ethyl alcohol) 70% isopropyl alcohol or ethanol are highly effective as an antimicrobial agent. In the presence of water, 70% alcohol causes coagulation of the proteins thus inhibiting microbial growth. Alcohols are not quite efficient when it comes to spores. The mode of action is by denaturing the proteins. Alcohols interfere with the hydrogen bonds present in the protein structure. Alcohols also dissolve the lipid membranes that are present in microorganisms. Disruption of the cell membrane is another property of alcohols that aids in cell death. Alcohols are cheap and effective antimicrobials. They are widely used in the pharmaceutical industry. Alcohols are commonly used in hand sanitizers, antiseptics, and disinfectants.
Phenol Phenol, also known as carbolic acid, was one of the first chemicals was used as an antimicrobial agent. It has high antiseptic properties. It is bacteriostatic at concentrations of 0.1%–1% and is bactericidal and fungicidal at 1%–2%. A 5% solution kills anthrax spores in 48 hr. Phenols are most commonly used in oral mouth washes and household cleaning agents. They are active against a wide range of bacteria, fungi and viruses. Phenol derivatives, such as thymol and cresol, are used because they are less toxic compared to phenol. These phenolic compounds have a benzene ring along with the –OH group incorporated into their structures. They have a higher antimicrobial activity. These compounds inhibit microbial growth by precipitating proteins which lead to their denaturation and by penetrating into the cell membrane of microorganisms and disrupting it. Hexachlorophene (
bisphenol) is used as a surfactant. It is widely used in soaps, handwashes, and skin products because of its antiseptic properties. It is also used as a sterilizing agent. Cresol is an effective antimicrobial and is widely used in mouthwashes and cough drops.
Aldehydes Aldehydes are highly effective against bacteria, fungi, and viruses. Aldehydes inhibit bacterial growth by disrupting the outer membrane. They are used in the disinfection and sterilization of surgical instruments. As they are highly toxic, they are not used in antiseptics. Currently, only three aldehyde compounds are of widespread practical use as disinfectant biocides, namely glutaraldehyde, formaldehyde, and ortho-phthalaldehyde (OPA) despite the demonstration that many other aldehydes possess good antimicrobial activity. However, due to its long contact time other disinfectants are commonly preferred. ==Physical==