Understanding Antibiotics and Knowing When to Use Them

Tasmin Tabassum

Freshman

School of Life Sciences

Independent University, Bangladesh

March 27th, 2017

Antibiotics are drugs used to treat infections that are caused by bacteria. They are also often referred to as antibacterials, as they only work on bacterial infections and have no effect on viral infections such as the common cold, measles, and the flu. Bacteria are single-celled microscopic organisms that are present everywhere, and only some of them cause disease.

Early on, Selman Waksman used the term "antibiotic" to describe chemicals or small molecules produced by microbes that inhibited or stopped the growth of other microbes. While the first antibiotics were all derived from bacteria and fungi, many existing ones were developed synthetically. Antibiotics drove a revolution in the history of medicine, and have since been used to save millions of lives. Before the discovery of antibiotics, people had to wait for the infection to recover on its own, rely on untested and often inefficient traditional cures, or cut out the infectious part out of the body

Like with all therapeutic drugs, antibiotics owe much of their success to specificity. Antibiotics affect bacterial cells, leaving human cells (as well as the cells of any other organism they are used to treat) undamaged. They target bacterial cells by binding to structures unique to bacteria. For instance, penicillin, the first discovered antibiotic, blocks formation of the thick cell wall of a certain kind of bacteria, and thereby kills the cell. Antibiotics can be bacteriostatic or bacteriocidal. Bacteriostatic antibiotics stop the bacteria from multiplying by interfering with metabolic processes associated with growth. Bacteriocidal antibiotics kill the bacteria by targeting a structure necessary for its survival, such as the cell wall or cell membrane. In the case of both bacteriocidal and bacteriostatic antibiotics, the rapid decrease in the number of bacteria helps the host immune system cope more effectively with the remaining bacteria.

Scott Alexander, based on Nature Review by Kim Lewis

Not all antibiotics are effective against all bacterial infections. Antibiotics that kill or inhibit only a specific few species of bacteria are known as narrow-spectrum antibiotics (for instance, penicillin), while antibiotics that affect a wide range of bacteria (for instance, quinolones, which block bacterial DNA replication) are called broad-spectrum antibiotics.

While antibiotics have greatly enhanced our ability to deal with bacterial infections, their use must be regulated for several reasons. It is important to realize that our bodies are home to trillions of bacteria that have important roles in our function and metabolism. Overuse of antibiotics often affects these bacteria as collateral damage, which in turn affects our health; broad-spectrum antibiotics, for instance, can cause diarrhea by inadvertently killing the beneficial bacteria present in our gut.

Bacteria are among the oldest living organisms to inhabit our planet, and are masters of adaptation. As we have discovered countless times since they were first used, bacteria become resistant to antibiotics. Resistance arises through mutations – changes in the genetic material of organisms, which are bacteria in this case – that result in changes in the structures targeted by an antibiotic, or cause the bacteria to neutralize or eject the antibiotic. While resistance occurs randomly, frequent and unregulated use of antibiotics selects for the multiplication of resistant strains by killing off competing, non-resistant strains of bacteria. These antibiotic resistant bacteria can be passed on to others from any healthy or ill person, and this resistance can spread between different bacteria living in our body by a process known as horizontal gene transfer. Antibiotics should therefore be used when absolutely necessary. Antibiotic courses should be seen through to completion to reduce the chances of resistance, if it arises, spreading through surviving bacterial populations.

To prevent antibiotic resistance from becoming more common, a balance must be struck between dosage, duration, and frequency of use. Antibiotics should not be prescribed or taken for viral infections, or in cases where a bacterial infection has not been verified by tests. Their use in farming and the food industry should be tightly regulated and minimized. Do you know how long it took for resistance to appear after penicillin was first mass-produced? Four years.

Tasmin is an enthusiastic science learner.