Antibiotic Resistance

Antibiotics and similar drugs, together called antimicrobial agents, have been used for over 70 years to treat people who have infectious diseases.  Since the 1940s, antibiotic use has changed medical care and public health by decreasing the amount of illness and death from infectious diseases.  When prescribed and taken correctly, antibiotics are of great value. 

Over years of use, bacteria have adapted to the antibiotics developed to kill them, making the drugs less effective.  Antibiotic resistance means that the bacteria are able to resist the effects of an antibiotic so the antibiotic will no longer prevent or cure the infection.  Some bacteria have developed resistance to a single antibiotic or related class of antibiotics.  Others have developed resistance to several antibiotics or classes; these organisms are often referred to as multidrug-resistant, or MDR, strains.  In some cases, the microorganisms have become so resistant that no available antibiotics are effective against them.

How much do you know about antibiotics?  Take this quiz to find out!  

How Does the Use of Antibiotics Lead to Antibiotic Resistance?

There are several ways that bacteria and other microorganisms can become resistant to drugs; one is the use of antibiotics.  Every time a person takes antibiotics, the susceptible bacteria are killed, but some bacteria are resistant to the antibiotics and survive.  Those that survive multiply and take over.  This is an example of natural selection or "survival of the fittest."  Repeated and improper uses of antibiotics are primary causes of the increase in drug-resistant bacteria. If antibiotics were not killing the susceptible bacteria, the resistant bacteria would not have the selective advantage to survive and might even die off.

To learn about the other ways that antibiotic resistance occurs, see the Food and Drug Administration's Center for Veterinary Medicine's nine-minute video explaining how antimicrobial resistance both emerges and proliferates among bacteria.

To learn which organisms are associated with antimicrobial resistance, visit the Centers for Disease Control and Prevention (CDC)’s website on diseases and pathogens associated with antimicrobial resistance.