What Drives the Spread of Antimicrobial Resistance?

Did you know that 1 in 5 resistant infections are caused by microbes from food and animals? That's more than 400,000 illnesses each year! While humans and animals do not become resistant to antimicrobial drugs, the microbes carried by humans and animals can. Antimicrobial resistance is spread through people, animals, and the environment. Learn more below. 

Antimicrobial use in animals can spread resistance

Animals treated with antimicrobials can carry resistant microbes. Food animals, like humans, are given antibiotics to treat infections, which will kill most bacteria. However, just like in humans, resistant bacteria can survive. Then, when food animals are slaughtered and processed, the resistant bacteria can contaminate the meat or other animal products. These resistant bacteria can also get into the environment, like our water and soil, from animal manure. When animal manure or contaminated water are used on fruits, vegetables, or other produce as fertilizer or irrigation, this can spread the resistant bacteria. 

There is also a longstanding practice of giving low doses of antibiotics to animals to promote their growth or increase feed efficiency. In fact, 70% of antibiotic use in the United States is in animals. While these animals grow bigger faster, the bacteria they carry are exposed to these low doses of antibiotics over a long period of time. This practice sets up the perfect breeding ground for resistant bacteria to develop. In the United States, as of 2017, medically important drugs (drugs we use for human health), are no longer allowed to be used for this practice.

People can still get sick from foodborne infections or having contact with food animals, which can be caused by resistant microbes. This can happen from eating/touching meat or seafood that is raw/undercooked and contaminated with resistant microbes or fruit or vegetables contaminated with resistant microbes. Touching or caring for animals without proper handwashing, or contact with animal poop when it gets into drinking water, water for growing crops, or swimming water can also lead to infections.

Antibiotics have been introduced to or spread to almost every ecosystem on earth

The environment is a huge source of antibiotic resistance. In fact, long before humans discovered and began to use antibiotics they were already present in the environment. Microbes produce antibiotics to gain a growth advantage and to defend themselves against competing organisms.The level of resistance genes detected in agricultural soil and in surface water is increasing. Recent work has even detected resistance genes in the air.

The life cycle of an antibiotic does not end when livestock are treated or a patient swallows a pill. In most cases, the antibiotic is excreted into urine or feces, ranging from 10-90% of still active compounds. These then go through the sewage system to waste-water treatment plants, but the treatment does not remove all the antibiotics. Antibiotics either leave the plant in treated water, or they become part of the sewar sludge and are introduced into the environment when the sludge is used as fertilizer or a filling material. Similarly, animal feces end up in manure storage tanks/lagoons, and the manure is used as fertilizer. When humans eat crops grown in manured soils or produce irrigated with contaminated water, they are exposed. Antibiotics also enter the water directly from pharmaceutical production facilities.

Human behaviors spread antimicrobial resistance too

The importance of frequently washing your hands

Resistant microbes spread directly on unclean hands, or from surfaces that unclean hands have touched, such as door handles and door knobs.

We have a supply and demand problem. The supply of new drugs is insufficient to keep pace with the increase in drug resistance caused by wide use of these drugs and microbes evolving resistance to them. The demand for these drugs is also badly managed - huge quantities of antibiotics are wasted globally on patients who do not need them. For example, a study found that in the United States, 40 million people are given antibiotics for respiratory issues annually. More than two-thirds, or 27 million of these patients are getting antibiotics unnecessarily - the infection was caused by a virus (which an antibiotic will do nothing for) or the condition was not an infection at all. In fact, up to one-half of all antibiotics prescribed in human medicine are not needed or are not prescribed appropriately. Doctors also prescribe the newer, more powerful antibiotics in cases that could be treated with older drugs, instead of keeping them in reserve for the drug-resistant infections where they are absolutely needed. For example the treatment of gonorrhea is done with the world's "last line" treatment to almost all patients, despite that 70-80% of cases would respond to the older drug. The number of multi drug-resistant gonorrhea cases are now increasing, which will lead to untreatable cases once this "last line" antibiotic fails.

AMR is a worldwide problem, requiring a global prospective on the problem in order to find viable solutions