antimicrobial-resistant staph bacteria


The Issue: Antibiotics and the Food Animal Industry

Since the 1940s, antibiotics have played a critical role in protecting the public’s health, and are responsible for saving millions of human lives. Unfortunately, inappropriate use of antibiotics is threatening their efficacy. The use of low doses of antibiotics by the modern food animal industry is responsible for drug-resistant bacteria emerging on farms which reach the general population through human or animal carriers, and through the food consumers eat. Because of the public health risks associated with antibiotic resistance, there is a push to end the use of low doses of medically important antibiotics in order to slow the development of antibiotic resistant bacterial strains.

What are Antibiotics?

Bacteria are everywhere, including on the skin and in the digestive system of humans. While bacteria are critical to normal bodily functions, some types can cause illness. In humans, antibiotics are used to treat health conditions caused by bacteria, including ear and skin infections, food poisoning, pneumonia, and meningitis. Antibiotics belong to a category of drugs called "antimicrobials," and include penicillin, tetracycline, amoxicillin and many other formulations that can kill or inhibit the growth of bacteria without causing significant harm to patients.

In the 1940s Penicillin was put into clinical use, and was one of the first drugs to prove widely effective against formerly untreatable bacterial infections. However, Penicillin’s efficacy against some common bacterial infections was short lived. By 1955, 13% of common Staphylococcus aureus infections were resistant to penicillin, and by 1988 this percentage was up to 91%.   1   Today, penicillin is no longer recommended as the first line of treatment of Staphylococcus infections because it is effective in less than 10% of new cases,   2   and the growing problem of antibiotic-resistant bacteria has compromised the efficacy of many other important antibiotics.

What are Antibiotic-Resistant Bacteria?

Similar to how immunization helps the human body fight disease by exposing the immune system to small amounts of a virus or bacteria, when bacteria are continually exposed to small amounts of antibiotics they can develop immunity to them. It’s a case of "survival of the fittest," with the strongest bacteria, that are least susceptible to a specific antibiotic, surviving, adapting and multiplying. These are called "resistant bacteria" because they have adapted to the point where antibiotics are no longer an effective means of killing them.   3   As a result, some antibiotics have lost their effectiveness against specific infectious diseases. The Centers for Disease Control estimates that each year in the US almost 2 million people acquire bacterial infections in hospitals, 70 percent of which are resistant to at least one commonly used antibiotic.   4

An example of antibiotic-resistant bacteria is staphylococcus aureus, a bacterium that is the most common cause of staph infections, and can also cause pneumonia, meningitis, toxic shock, skin abscesses, heart valve infections and other serious and deadly medical conditions.   5   Many strains of s. aureus are now resistant to the antibiotics oxacillin, penicillin and amoxicillin, and strains of the disease have begun developing resistance to newer drugs like methicillin and vancomycin, powerful drugs once considered ‘last resort' antibiotics for only the most serious infections.   6   7   The threat of prolonged illness or death from an S. aureus infection has increased as it has become more resistant and fewer drugs are able to effectively control or eliminate it. According to a recent study published in the Journal of the American Medical Association, approximately 19,000 deaths per year in the United States can be attributed to infection with Invasive Methicillin-resistant Staphylococcus aureus, a number greater than annual U.S. deaths from AIDS.   8

The problem of antibiotic resistance has accelerated through overuse of antibiotics in humans and animals. Over-prescribing antibiotics for conditions caused by viruses like the flu or common cold, which antibiotics cannot treat, contributes to antibiotic resistance. Even when antibiotics are used for bacterial infections, studies have shown that antibiotic resistance can still arise from their use.   9   10   Failure to complete the prescribed antibiotic regimen for a bacterial infection is another common contributor to the development of antibiotic resistance.   11

Antibiotics and the Animal Industry

Industrial farms  have been adding antibiotics to livestock feed since 1946, when studies showed that antibiotics caused animals to grow faster and put on weight more efficiently, increasing meat producers' profits.   13   Between 1985 and 2001, the use of antibiotics in feed for industrial livestock production rose a startling 50%.   14   Today, antibiotics are routinely fed to livestock, poultry, and fish on industrial farms to promote faster growth and to compensate for the unsanitary conditions in which they are raised.   15   According to a new report by the FDA, approximately 80 percent of all antibiotics used in the United States are fed to farm animals.   16   This means that in the United States only 20 percent of antibiotics, which were originally developed to protect human health, are actually used to treat infections in people.

Modern industrial farms are ideal breeding grounds for germs and disease. Animals live in close confinement, often standing or laying in their own waste, and are under constant stress that inhibits their immune systems and makes them more prone to infection.   17 When drug-resistant bacteria develop in industrial livestock facilities, they can reach the human population through food, the environment (i.e., water, soil, and air), or by direct human- animal contact.   18

One major way in which antibiotics and antibiotic resistant bacteria enter the environment is via animal manure. Industrial livestock operations produce an enormous amount of concentrated animal waste—over one billion tons annually—often laden with antibiotics and their residues, as well as antibiotic-resistant bacteria. It is estimated that approximately 75 percent of all antibiotics given to animals are not fully digested and eventually pass through the body and enter the environment,   19   where they can encounter new bacteria and create additional resistant strains.   20   With huge quantities of manure routinely sprayed onto fields surrounding CAFOs, antibiotic resistant bacteria can leech into surface and ground water, contaminating drinking wells and endangering the health of people living close to large livestock facilities.   21   Bacteria can also be spread by insects that come in contact with animal waste. A study conducted by researchers at Johns Hopkins University examined flies near broiler poultry operations and found that many of the flies living near these operations carried antibiotic resistant enterococci and staphylococci. If these flies travel to nearby homes, they could transport these drug resistant bacteria from the farm to neighboring communities.   22

Antibiotic Resistance and Public Health

Antibiotic-resistant bacteria are a growing public health crisis because infections from resistant bacteria are increasingly difficult and expensive to treat. The National Academy of Sciences calculates that increased health care costs associated with antibiotic-resistant bacteria exceed $4 billion each year in the United States alone—a figure that reflects the price of pharmaceuticals and longer hospital stays, but does not account for lost workdays, lost productivity or human suffering.   23

Dr. Margaret Chan, the Director-General of the World Health Organization, released a statement on World Health Day 2011 about the bleak future of treating bacterial infections if no steps are taken to slow the development of antibiotic resistant bacterial strains. She warned that “in the absence of urgent corrective and protective actions, the world is heading toward a post-antibiotic era, in which many common infections will no longer have a cure and, once again, kill unabated.”   24  Although everyone is at risk when antibiotics stop working, the threat is greatest for young children, the elderly, and people with weakened immune systems, including cancer patients undergoing chemotherapy, organ transplant patients and, in general, people whose health is compromised in some way.


In 2011, an amendment to the Federal Food, Drug, and Cosmetic Act called the Preservation of Antibiotics for Medical treatment, was introduced in the U.S. House of Representatives. The goal of the amendment is to create legislation that is focused on protecting the effectiveness of antibiotics used in treating human and animal diseases.   24   In early 2011, it was referred to the House Energy and Commerce Committee and the Subcommittee on Health, as well the House Committee on Rules. Following reports by these committees, the act will be sent back to the House for voting.   25   If the bill is passed, it will ban the use seven classes of antibiotics that are medically significant to humans for use by the food animal industry, as well as restrict the use of many other antibiotics in animal feed.

Sustainable Alternatives

Ending the routine use of antibiotics in animal agriculture is not only critical, it is possible and economically feasible. According to a study conducted by researchers at Johns Hopkins University, the increased selling price of chickens fed growth promoting antibiotics (or GPAs) did not offset the increased cost of the feed, resulting in a higher overall cost to the farmer. The study found that the use of GPAs resulted in an average loss in value per chicken of $0.0093, or about 0.45%. Along with expected decreases in health care costs that would stem from reducing the number of drug resistant infections, there is evidence to show that eliminating GPAs would be profitable for both farmers and the public as a whole.   26

Today, many animal farmers do not use antibiotics at all, in large part because they don’t have to compensate for unhealthy conditions associated with CAFO production systems. On these types of farms, animals are raised in clean environments with adequate space to reduce animal-stress and the likelihood of infections.   27   While these types of farms may use antibiotics, they only do so to treat acute infections in sick animals, just as they are used to treat infections in humans.

Federal standards prohibit antibiotic use in animals whose meat will be certified organic.   In Eat Well Guide, farms where antibiotics are never given to animals carry the label "no antibiotic use," while those where antibiotics are only used to treat a sick animal carry the label "no routine antibiotic use." In these instances, a suitable amount of time must pass after an animal is treated and before its meat, milk or eggs can enter the food supply.


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