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Medicine

Antibiotics

Antibiotics are medicines used to prevent and treat bacterial infections. They are ineffective against viruses, and their misuse has led to the global health threat of antimicrobial resistance.

1928
Discovery of penicillin
Year
~70%
of global antibiotic use is in agriculture
Estimate
1.27M
deaths directly caused by antibiotic-resistant infections in 2019
Deaths
1

Definition and mechanism of action

Antibiotics are a class of antimicrobial drugs that specifically target bacteria, either killing them (bactericidal) or inhibiting their growth (bacteriostatic). They work by interfering with essential bacterial processes such as cell wall synthesis, protein synthesis, DNA replication, or metabolic pathways. For example, penicillins and cephalosporins disrupt cell wall synthesis, while tetracyclines and macrolides inhibit protein synthesis.1

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History and discovery

The modern era of antibiotics began with Alexander Fleming's discovery of penicillin in 1928, but the term 'antibiotic' was coined by Selman Waksman in 1942. The first clinical use of penicillin was in the 1940s, revolutionizing medicine. However, the concept of using molds to treat infections dates back to ancient civilizations, such as the use of moldy bread in Egypt and China.2

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Types and classifications

Antibiotics are classified by their chemical structure, mechanism of action, and spectrum of activity. Major classes include beta-lactams (penicillins, cephalosporins), macrolides, tetracyclines, aminoglycosides, fluoroquinolones, and sulfonamides. They can be narrow-spectrum (targeting specific bacteria) or broad-spectrum (affecting a wide range).1

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Uses in medicine and agriculture

Antibiotics are used to treat bacterial infections in humans and animals. In agriculture, they are used for disease treatment and prevention, and as growth promoters in livestock. This agricultural use contributes significantly to the selection of resistant bacteria, which can spread to humans through the food chain and environment.3

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Antimicrobial resistance

Antimicrobial resistance (AMR) occurs when bacteria evolve to survive antibiotic exposure. Overuse and misuse of antibiotics accelerate this process. The WHO has declared AMR one of the top 10 global public health threats. In 2019, an estimated 1.27 million deaths were directly attributable to drug-resistant infections.4

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Lesser-known aspects

Beyond the well-known story of penicillin, there are many lesser-known facets of antibiotics. For instance, the first antibiotic used clinically was actually prontosil, a sulfonamide, in 1935. Also, some antibiotics are produced by bacteria themselves, not just fungi. The discovery of antibiotics from soil bacteria by Waksman led to streptomycin, the first treatment for tuberculosis. Additionally, antibiotics have been used as growth promoters in livestock since the 1940s, a practice now being phased out in many regions due to resistance concerns. Another niche area is the use of antibiotics in plant agriculture to combat bacterial plant diseases, such as fire blight in apples and pears.

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Future directions

To combat AMR, researchers are exploring new antibiotics, phage therapy, and alternative approaches like CRISPR-based antimicrobials. There is also a push for antibiotic stewardship programs to optimize use. The development of new drugs is challenging due to economic and regulatory hurdles, but initiatives like the Global Antibiotic Research and Development Partnership (GARDP) aim to address this.5

Glossary

Bactericidal
An agent that kills bacteria.
Bacteriostatic
An agent that inhibits bacterial growth.
Broad-spectrum antibiotic
An antibiotic effective against a wide range of bacteria.
Narrow-spectrum antibiotic
An antibiotic effective against specific types of bacteria.
Antimicrobial resistance (AMR)
The ability of microorganisms to resist the effects of drugs.

Antibiotics are a cornerstone of modern medicine, but their effectiveness is threatened by resistance. Responsible use and continued research are essential.

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