Causes and Spread of AMR

Antimicrobial Resistance and Health

Consistent misuse and overuse of antibiotics in the community and in hospital settings has allowed antimicrobial resistance to become a global health threat. Moreover, experience has shown that uncontrolled introduction and prescribing of new drugs has the effect of worsening the problem by rendering bacteria resistant to more than one antimicrobial agent.

Examples of how antibiotics are misused:

In treating human infections

Taking antibiotics when they are not the appropriate course of treatment. The US Centers for Disease Control and Prevention (CDC) estimates that more than 30% of outpatient antibiotic prescriptions are provided unnecessarily e.g., to patients with viral infections.
Patients demanding antibiotics even when they are not needed
Taking antibiotics incorrectly - e.g.,

Not completing the full course of treatment
Skipping or missing doses
Saving antibiotics for a future infection
Taking antibiotics that were prescribed for someone else

Health-care providers using broad-spectrum antibiotics in cases where narrow-spectrum antibiotics would work equally well

In agricultural use

Adding of low levels of antibiotics in the diets of chicken and pigs as growth promoters even when the animals are not infected (Carpenter 1950)
Using antibiotics to manage infections in unsanitary animal husbandry and unhygienic farming practices

How does resistance spread?

In addition to antibiotic misuse and overuse, poor infection prevention is increasing challenges due to antibacterial resistance. It is also crucial to remember that antibacterial resistance is a global health issue, and sanitation infrastructure is not the same worldwide. In low-income countries, the lack of potable water sources, where pathogenic microbes may be found, and effective sanitation practices are also aggravating the resistance crisis. For example:

Unhygienic food preparation, incomplete cooking of meats, ingestion of raw fish and other seafood all increase the likelihood of acquiring a bacterial infection
Lack of proper handwashing and poor sanitation allows bacterial infections to easily spread from person to person in the community, thereby increasing the spread of drug-resistant infections.
In the hospital environment, drug resistance may spread if carabapenem resistant Enterobacterales (CRE) infections can easily spread directly to other patients through contact, or indirectly on the unwashed hands of physicians and other health care providers.

As antibacterial drugs continue to be misused and overused, development of resistance to these agents is accelerating. Learn more about antibiotic resistance mechanisms.

References

Antibiotic Resistance Threats in the United States, 2013. (2013). Retrieved from https://www.cdc.gov/antimicrobial-resistance/media/pdfs/ar-threats-2013-508.pdf?CDC_AAref_Val=https://www.cdc.gov/drugresistance/pdf/ar-threats-2013-508.pdf

Carpenter, L.E. (1950) Effect of aureomycin on the growth of weaned pigs. Arch Biochem. 27(2):469-71. PMID: 14771917.

Infection Prevention, Control, and Surveillance. (2016). Retrieved from https://amr-review.org/sites/default/files/Health infrastructure and surveillance final version_LR_NO CROPS.pdf

Tackling Drug-Resistant Infections Globally. (2016). Retrieved from https://amr-review.org/sites/default/files/160525_Final paper_with cover.pdf

March 2025, Gauri Patel; Reviewed by Dr. Tanaya Bhowmick
https://doi.org/10.2210/rcsb_pdb/GH/AMR/about/cause-spread