Learn about antibiotics

What are antibiotics?

Antibiotics are substances that kill or slow the growth of bacteria. Bactericidal antibiotics kill bacteria, while bacteriostatic antibiotics stop them from multiplying.


What are bacteria?

Bacteria are microscopic, single-celled organisms. Bacteria usually come in one of three basic shapes: rod-shaped (bacilli), spherical (cocci) and helical (spirilla). Bacteria may also be classified as Gram-negative (such as E. coli) or Gram-positive (such as Staph. aureus). Gram-negative bacteria have two membranes, while Gram-positive bacteria have only one. This extra membrane makes it harder for drugs to penetrate Gram-negative bacteria. There are thus fewer treatment options for infections caused by Gram-negative bacteria.


Bacteria live in and on every environment including the soil, ocean, plants, animals and human body. Most bacteria in our body are harmless, or serve an important purpose, such as digesting food. They also help to prevent disease by making the body less hospitable to harmful bacteria (pathogens). When bacteria break through the body’s defences and begin to multiply, they cause an infection.


Why can’t antibiotics treat viruses?

Viruses are smaller than bacteria and are not cells. They are parasites and grow within cells, and so they need a host human or animal cell to multiply. Antibiotics cannot kill viruses because they work on bacterial systems that viruses do not have. Using antibiotics when they are not needed, including against viral infections like commons colds and the flu, contributes to antibiotic resistance.


What is antibiotic resistance?

Bacteria, not people’s immune systems, develop resistance to antibiotics. Bacteria reproduce quickly and some can double their numbers every 20 minutes. A very small number of bacteria may naturally evolve to develop resistance to certain drugs. However, when repeatedly exposed to antibiotics, the vulnerable bacteria die, leaving behind the drug-resistant bacteria, so-called “superbugs,” to multiply. Inappropriate use of antibiotics creates a favourable environment for drug-resistant bacteria to grow.

Which bacterial infections are becoming resistant?

Antibiotic resistant bacteria are found in all parts of the world. A growing list of infections – such as pneumonia, bloodstream infections, gonorrhoea, urinary tract infections, skin disorders and foodborne disease – are becoming harder, and sometimes impossible, to treat. The World Health Organization has identified a list of drug-resistant priority pathogens for which new drugs are needed and that represent the greatest threat to health. 


Why have so few new antibiotics been developed?

Most pharmaceutical companies are no longer developing new antibiotics. Half of all antibiotics used today were discovered during the 1950s. Since that time, the discovery and development of antibiotics has become more complex, time-consuming and expensive. It can take over a decade and $1.5 billion to develop a new antibiotic treatment with an overall success rate of just 10%. Moreover, because new antibiotics are restricted to “last resort” cases to slow the emergence of resistance, sales opportunities are limited. These factors limit the profitability of antibiotics and thus disincentivize development.


How can I prevent antibiotic resistance?

Antibiotic resistance is fostered by the inappropriate use of antibiotics, as well as poor infection prevention and control in the environment, homes and hospitals. WHO has published recommendations for individuals, healthcare workers, policymakers and the healthcare industry to limit the spread of drug-resistant bacteria.