Facts about antimicrobial resistance

Treatment with antimicrobials is intended to kill pathogenic bacteria. Unfortunately, antimicrobials also cause the bacteria to protect themselves by developing resistance to the type of antimicrobials that are used to treat them. Bacteria that are resistant to several types of antimicrobials are called multiresistant.

Resistant bacteria can be transmitted between humans, and bacteria can infect each other with resistance. However, resistant bacteria are poor at surviving if antimicrobials are not present. Therefore, it is important to have an overall focus on using as few antimicrobials as possible in the treatment of both animals and humans.

Bacteria know no borders. Therefore antimicrobial resistance in one country can cause problems outside of its borders. As such the use of antimicrobials in both animals and humans is a global problem. The World Health Organization, WHO, considers antimicrobial resistance to be one of the biggest threats against human health.

Not all antimicrobials are the same. Some are narrow spectrum and affect only individual groups of bacteria. They are used when you know which bacteria are causing the disease. Others are broad spectrum and affect numerous groups of bacteria at the same time. They can therefore be used to treat a disease before it is known which bacteria is the cause. However, they often also kill useful and harmless bacteria such as bacteria in the intestine, which may lead to the emergence of resistant bacteria.

Not all antimicrobials are equally important in the treatment of humans. WHO has declared a number of antimicrobials to be ’critically important’, because they are the only or one of only a few antimicrobials, which can be used to treat serious or life-threatening infections in humans. These types include carbapenems, third and fourth-generation cephalosporins, fluoroquinolones and macrolides.


Frank Møller Aarestrup
Professor, Head of Research Group
National Food Institute
+45 35 88 62 81