What Are Antibiotics And How Do They Kill Bacteria?

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Antibiotics are substances that are used to kill or inhibit the growth of bacteria. They work by either preventing the bacteria from developing new cells, damaging its DNA, or causing the bacterial cells to rupture. Antibiotics are not effective against viruses, and many people still confuse the idea of antibacterial with antimicrobial.

We all know the feeling… our head is aching, our mouth is dry, and our stomach is tied up in knots. We’re starting to get sick, so we make our way to the doctor’s office in the hopes that he can figure out what’s wrong.


For thousands of years, getting sick was extremely dangerous, as medical science wasn’t nearly as advanced as it is now. If you fell ill, there was a good chance that you could die, simply because diagnosing particular illnesses was difficult enough, let alone curing them. Fortunately, less than a century ago, humanity discovered a new weapon in the constant struggle for survival.

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The Accidental Discovery

The year was 1928, and a man named Alexander Fleming was returning to his laboratory after a long weekend. Perhaps he had been in a rush before he left, but he hadn’t properly stored his petri dishes, in which he was studying a Staphylococcus strain of bacteria. However, what he found was that mold had begun to grow in the dishes, and strangely enough, it had completely halted the growth and spread of the bacteria sample.


Penicillin notatum was the mold that had grown and led to that discovery, and it remains one of the most important Eureka moments in scientific history. Penicillin remains the most famous type of antibiotic in the world, and is used for a wide range of conditions, including Streptococcus, Meningococcus, and many others.

However, antibiotics are not effective against viruses, and many people still confuse the idea of antibacterial with antimicrobial. Antibiotics use in the 20th century revolutionized medicine around the world, and led to the production of vaccines for many deadly diseases that had ravaged populations for centuries.

Now, while penicillin was the first material known to have antibiotic properties, it was not effective against all types of bacterial infections, so other antibiotics had to be developed and studied. This led to the rise of everything from polymyxins and tetracyclines to quinolones and carbapenems. Antibiotic substances have been tailored to successfully treat hundreds of different bacterial infections over the years, and have become quite complex as we’ve learned more about bacteria itself.

Also Read: What Is Antibiotic Resistance And Why Is It Happening So Quickly?

Positive Or Negative? It Makes A Difference!

Bacteria tend to fall in one of two categories: gram-positive or gram-negative. Gram-positive bacteria have thin, single-layer cell walls that are relatively easy to permeate. Gram-negative bacteria boast tougher walls that are two layers, thus making it more difficult to enter. If you want an antibiotic substance to work, it needs to be able to breach one or both of these bacterial walls.


Antibiotics had to be understood before being customized to battle different bacterial strains, and developing an attack plan was essential. Antibiotic materials neutralize bacteria either by preventing it from developing new cells, damaging its DNA, or causing the bacterial cells to rupture. However, not every antibiotic can do those things, and not every bacterial cell will respond to the same pharmaceutical tactics.

There are broad-spectrum and narrow-spectrum antibiotics on the market, and you will be prescribed one of these varieties depending on your diagnosis. Broad-spectrum antibiotics can safely eliminate gram-positive and gram-negative bacteria, making them the heavy hitters of the antibacterial world. Narrow-spectrum are able to treat specific types of bacterial infection, either gram-positive or gram-negative, but not both. Broad-spectrum antibiotics treat urinary tract infections, ulcers, acne, pneumonia, and anthrax, among others, while narrow-spectrum antibiotics handle middle ear infections, sinusitis, chlamydia and pertussis.


Clearly, both varieties are crucial for protecting our immune system, but what happens when the antibiotics STOP working?

Also Read: What Is A Bacteriophage?

The Tragic Problem Of Antibiotics

As explained above, the rise in popularity of antibiotics substances was incredible, and antibiotics were soon being used all around the world, trusted as a reliable solution to hundreds of medical conditions, some of which weren’t even bacterial in origin. Furthermore, doctors began prescribing powerful antibiotics at the drop of a hat, while agriculture experts began treating livestock with antibiotics to keep them healthier.

Essentially, the world and its food supply was being flooded with antibiotics, which meant two things: bacterial infections were declining, but the ability of bacteria to adapt and evolve was increasing. Antibiotic-resistant bacteria remains one of the major threats to the human population, and the problem is only going to get worse. When antibiotics are improperly used, such as using them when not necessary or not taking all of the prescribed medication, bacteria have an ability to react to that antibiotic substance and adapt. When that bacteria is then passed on to someone else, and the same antibiotic is prescribed, it will be less effective.


While this seems like a small problem, it has already killed tens of thousands of people. Bacteria that has become immune to antibiotics are hugely dangerous, and an outbreak of that variety is treated very seriously. One of the most commonly referenced instances of this is MRSA (Methicillin-resistant Staphylococcus aureus), which commonly affects patients in hospitals and is labeled a “superbug”. It kills about 20,000 people every year, many of which are children. Gonorrhea and certain other infections have also developed immunity to certain antibiotic strains. Roughly 2 million people suffer from antibiotic-resistant bacterial infections every year, but that number is expected to grow as antibiotic resistance increases.

Furthermore, antibiotics can often neutralize or destroy the beneficial bacteria in the human body while destroying the dangerous strains, thus leaving the gut and other parts of the body unprotected. Before that beneficial bacteria can be replaced (probiotics, healthy diet etc.) the body is even more susceptible to other infections, perhaps those that are already resistant to the medication. It’s never a good thing when the medication kills the good guys and leaves the bad ones standing!

Where Do We Go From Here?

There are a number of ways that we can improve humanity’s chances and avoid being wiped off the face of the earth by a bacterial superbug. First of all, doctors need to stop prescribing antibiotics unless the case is absolutely necessary, and should try to use narrow-spectrum antibiotics whenever possible, which are customized to a specific bacterial strain instead of “blanket” coverage of broad-spectrum varieties.

Hygiene is always key, as well as sanitation in parts of the world where infections are common and medical facilities are few and far between. Food derived from livestock animals that are given long-term, low-dose antibiotics should be avoided, and greater regulation should be put in place to ensure that we aren’t making entire populations susceptible to antibiotic-resistant strains.


The real danger is that launching a new antibiotic is a long and costly process, taking a decade, on average, and upwards of $250 million. We have only developed a limited number, and only produce one or two new types of antibiotic every year. We’ve basically gotten into an arms race with bacterial agents around the world.

Can we curb our use of antibiotics and prevent the spread of dangerous infections? Or will bacteria continue to adapt and evolve against us until a superbug emerges that causes a global pandemic? Only time will tell!

References (click to expand)
  1. Antibiotic - Wikipedia. Wikipedia
  2. Pinpointing how antibiotics work | MIT News. news.mit.edu
  3. How Antibiotics Work - www.nd.edu:80
  4. What is an Antibiotic? - Learn Genetics Utah. The University of Utah
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John Staughton is a traveling writer, editor, publisher and photographer who earned his English and Integrative Biology degrees from the University of Illinois. He is the co-founder of a literary journal, Sheriff Nottingham, and the Content Director for Stain’d Arts, an arts nonprofit based in Denver. On a perpetual journey towards the idea of home, he uses words to educate, inspire, uplift and evolve.