Definition of Terms, Antimicrobial (Drug) Resistance


Microbes are living organisms that multiply frequently and spread rapidly. They include bacteria (e.g., Staphylococcus aureus, which causes some staph infections), viruses (e.g., influenza, which causes the flu), fungi (e.g., Candida albicans, which causes some yeast infections), and parasites (e.g., Plasmodium falciparum, which causes malaria). Some microbes cause disease and others exist in the body without causing harm and may actually be beneficial.

Antimicrobial (Drug) Resistance

Microbes are constantly evolving enabling them to efficiently adapt to new environments. Antimicrobial resistance is the ability of microbes to grow in the presence of a chemical (drug) that would normally kill them or limit their growth.

Antimicrobial resistance makes it harder to eliminate infections from the body as existing drugs become less effective. As a result, some infectious diseases are now more difficult to treat than they were just a few decades ago. As more microbes become resistant to antimicrobials, the protective value of these medicines is reduced. Overuse and misuse of antimicrobial medicines are among the factors that have contributed to the development of drug-resistant microbes.

View the illustration: What is drug resistance?

Examples of Antimicrobial (Drug) Resistance

Examples of Antimicrobials

  • Tetracycline, an antibiotic that treats urinary tract infections
  • Oseltamivir, also known as Tamiflu, an antiviral that treats the flu
  • Terbinafine, also known as Lamisil, an antifungal that treats athlete’s foot
Content last reviewed on February 18, 2009