Antimicrobial

An antimicrobial is any agent that manages microorganisms. These agents function in two primary ways. A microbicide kills the microorganisms directly. A bacteriostatic agent stops the microorganisms from growing. Scientists group these medicines by the specific microbes they target. For example, antibiotics are used for bacteria. Antifungals are used for fungi. Antivirals treat viral infections. Antiparasitics are used for diseases caused by parasites. Some treatments are considered broad-spectrum because they are active against multiple classes of pathogens at once.

Antimicrobials are also classified by their intended function and application. Disinfectants are non-selective agents like bleach. They kill a wide range of microbes on surfaces to prevent illness. Antiseptics are applied to living tissue. These help reduce infection during surgical procedures. Antibiotics are used to destroy microorganisms inside the human body. While the term antibiotic once only described substances from living organisms, it now includes synthetic agents like sulfonamides or fluoroquinolones. Modern technology has even created porous media that kill microbes on contact.

Different classes of drugs target specific biological structures. Antibacterials are classified as beta-lactams, macrolides, quinolones, tetracyclines, or aminoglycosides. This classification depends on their chemical composition and pharmacodynamics. Antifungals exploit differences between mammalian and fungal cells. Because both humans and fungi are eukaryotes, their cells are similar at the molecular level. This makes it harder to find a target that does not harm the host. Consequently, antifungals can cause life-threatening side effects if used improperly. Antivirals are distinct from viricides, which deactivate virus particles outside the body. Some antivirals, like protease inhibitors, treat retroviruses such as HIV. Others, like acyclovir, treat herpes viruses.

Humanity has used antimicrobials for at least 2,000 years. Ancient Egyptians and Greeks used plant extracts and molds to treat infections. In the 19th century, Louis Pasteur observed antagonism between different bacteria. His work on fermentation helped distinguish between anaerobic and aerobic bacteria. This knowledge allowed Joseph Lister to implement antiseptic methods. Lister sterilized surgical tools and debrided wounds. These techniques drastically reduced deaths from surgical infections. Pasteur's microbiology also led to vaccines for rabies and anthrax.

On September 3, 1928, Alexander Fleming discovered penicillin. He noticed a fungus called Penicillium rubens separated bacteria colonies in a Petri dish. In 1942, Howard Florey, Ernst Chain, and Edward Abraham purified penicillin for medicine. They earned the Nobel Prize in Medicine in 1945. The antibiotic era began with sulfonamide drugs in 1936. A "golden" period of discovery followed from 1945 to 1970. During this time, many diverse and effective agents were developed. Selman Waksman also won a Nobel Prize for developing 22 antibiotics, including Streptomycin.

There are significant concerns regarding the misuse of these agents. Using antimicrobials too much in humans, animals, and plants drives antimicrobial resistance, or AMR. This happens when pathogens develop the ability to survive the drugs. AMR was directly responsible for 1.27 million global deaths in 2019. It also contributed to 4.95 million deaths. Since 1980, the introduction of new clinical antimicrobials has declined. This is partly due to the enormous expense of drug development. Physicians often misuse antibacterials for viral respiratory infections, which does not help.

Scientists are looking for new ways to combat resistant pathogens. One strategy involves using metagenomics to find compounds in unknown microorganisms. Another method is developing small-molecule libraries for specific bacterial targets. Non-pharmaceutical antimicrobials are also used. Organic acids like citric or acetic acid are used in food products. For instance, beef carcasses are sprayed with acids to reduce E. coli. Copper is another natural antimicrobial. Copper-alloy surfaces can kill E. coli and Staphylococcus. The EPA has approved these surfaces for use in subways and healthcare facilities.