Press Centre

Bacteria and Antibiotics Backgrounder

What are bacteria?

Bacteria are among the most abundant organisms on earth. We interface with millions of them each day. They are present in the air we breathe and the food we eat, and they also live on most surfaces we routinely touch.

Bacteria are single-celled, living organisms containing a single strand of DNA. They typically reproduce by simply dividing into two new daughter cells, each containing an exact copy of the parent cell's DNA. Each daughter cell, in turn, gives rise to two new daughter cells, and so on. Under the right environmental conditions, a given population of bacteria can double in size in as little as 20 minutes.

Are all bacteria harmful?

No. The presence of bacteria in the body does not mean you will get a disease. Our bodies are full of bacteria that generally do not cause any harm. It is the strains of bacteria which produce harmful toxins and other chemical substances that make us ill. "Disease" occurs when these dangerous strains gain entry into the body. Our bodies are simply reacting to the presence of these noxious toxins.

What is an antibiotic?

An antibiotic is any substance that interferes with the ability of bacteria to function normally (remember, bacteria are living organisms). It may either inhibit their growth (bacteristatic antibiotic) or kill the bacteria (bactericidal antibiotic).

Antibiotics are used to treat bacterial infections ranging from life-threatening meningitis to common problems like acne and strep throat. Antibiotics will not help cure illnesses caused by viruses, such as colds or flu.

How do antibiotics work?

Different antibiotics have different ways of fighting bacteria. For example, they can work by:

Changing the cell wall structure of bacteria - The bacteria literally rupture due to the penetration of fluids through the cell wall.
Examples: penicillin (and its derivatives ampicillin and cloxacillin), cephalosporins (e.g., cefoxitin), vancomycin
Interfering with protein production - Proteins are needed to ensure the manufacture of new bacteria to replace old, dying bacteria. Some antibiotics interfere with the ability of bacteria to make proteins that are used to build important parts of the cell.
Examples: tetracycline, aminoglycosides (e.g., gentamicin, tobramycin), macrolides (e.g., erythromycin, azithromycin, clarithromycin)
Interfering with DNA synthesis - These antibiotics interfere with the production of new chromosomes, the cell's genetic information.
Examples: quinolones (ciprofloxacin)

What is antibiotic resistance?

When bacteria develop the ability to defend themselves against the effect of an antibiotic, then they are said to have acquired antibiotic resistance.

How do bacteria develop resistance to antibiotics?

Over the years, common antibiotics have been used so extensively that many of the bacteria that cause disease have grown resistant to them.

Bacteria are very good at re-inventing themselves. They are constantly mutating and adapting their genetic structure to their environment. In the presence of antibiotics, the more susceptible bacteria are killed off, but the resistant ones that survive are given the chance to grow. These resistant bacteria can cause infections that are harder to treat, which means that antibiotics won't work as well when they are really needed to fight life-threatening infections.