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Obesity and antibiotic usage correlation, 2010
States with higher numbers of antibiotic prescriptions tend also to have populations with higher percentages of obesity. (Source: Annals of the American Thoracic Society 2014 & Martin Blaser, MD)

Better Antibiotic Stewardship Needed to Offset Resistance and Other Effects

November 9, 2015

The discovery of antibiotics was one of the most significant advances in medical care in the 20th century. However, more than seven decades after penicillin was first used to treat infections, the use of these medications has become extremely and, according to some, unnecessarily widespread both in patient care and livestock management. A coordinated strategy curtailing use of these drugs is necessary in order to ensure their long-term effectiveness and to offset other impacts of antibiotic use, according to many medical professionals.

A substantial part of the problem is that wide and relatively indiscriminate use of antibiotics has led to a rise in microbial strains resistant to the drugs. This has required using new classes of antibiotics, but research has not been able to keep up with the rise of resistance. All classes of antibiotics in use today were first discovered prior to the mid 1980s.

"At least 2 million people per year in the U.S. get infections that are resistant to antibiotics and 23,000 die as a result of these infections," said Tom Frieden, Director of the Centers for Disease Control, in a briefing discussing drug-resistant health threats. "We talk about a pre-antibiotic era and an antibiotic era. If we're not careful, we will soon be in a post antibiotic era."

Beyond the obvious problem of drug-resistant infections, however, doctors have come to understand that the widespread use of antibiotics may also be impacting our health and environment in other ways.

"The overuse of antibiotics may have permanently changed our microbiome," said Dr. Martin J. Blaser, Director of the Human Microbiome Program, NYU School of Medicine, who addressed the CCST Council on October 27. "There is a correlation between the amount of antibiotic use and the distribution of obesity."

Antibiotics are among the most frequently prescribed medications in the US; in 2010, five of the top eight prescriptions for children were antibiotics, including the top two (Amoxicillin and Azithromycin). Overall for all age groups, 258 million outpatient antibiotic prescriptions were dispensed in 2010.

"There is an association between childhood use of antibiotics and obesity," said Blaser. "Moreover, there's an association between antibiotic use by children and their mothers, while pregnant, with allergies to cow's milk. Antibiotic exposure also has been associated with increased risk for type 2 diabetes. The damage done to our own microbes with these treatments may be leading to severe health consequences."

The problem extends beyond human prescriptions, however, because antibiotics have become widely used in the beef, pork, and poultry industries to promote the growth of livestock.

"75% of antibiotics used for growth promotion are not absorbed by the animal body," said Dr. Lee W. Riley, Professor and Head, Division of Infectious Disease and Vaccinology School of Public Health, UC Berkeley, who also spoke at the Council meeting. "Between two and eighteen million pounds of antibiotics are released into the environment each year by animal waste alone."

Riley noted that this means humans receive substantial environmental exposure to antibiotics, especially in areas of the country where animal production is concentrated. Many antibiotics used in animals endure for a long time in the soil (Virginiamycin, used as a growth promoter, and Cyclosporin A, e.g.) or are simply not degradable in soil sediments (Quinolones, which have been used to prevent poultry disease). Moreover, antibiotics are not officially recognized as a form of pollution.

California policymakers have taken steps to address the issue. In 2014 the California Department of Public Health set in motion an Antimicrobial Stewardship Program Initiative; California is the first and, as of now, remains the only state to enact antimicrobial stewardship legislation. The initiative requires hospitals to adopt and implement an antimicrobial stewardship policy. Additional bills signed into law in 2015 expand the initiative to include veterinarians and skilled nursing facilities (SB 361) and require antimicrobials to be administered to livestock by prescription only, not for weight gain (SB 27). However, for many members of the healthcare community, such measures are only the beginning.

"We have demonstrated, with better infection control measures and better antimicrobial stewardship, that antimicrobial usage can be reduced while maintaining effective patient care," said Blaser. "Progress can be made. But there's much that needs to be done."