The Centers for Disease Control and Prevention (CDC) has issued a report examining the impact of antibiotic-resistant bacteria on human health. Titled Antibiotic Resistance Threats in the United States, 2013, the report categorizes bacterial strains as either urgent threats, serious threats or concerning threats according to their clinical and economic impacts, incidence, 10-year projection of incidence, transmissibility, availability of effective antibiotics, and barriers to prevention. Among the bacteria identified by CDC as serious threats are drug-resistant Campylobacter, drug-resistant non-typhoidal Salmonella, methicillin-resistant Staphylococcus aureus (MRSA), and drug-resistant tuberculosis.

In particular, the agency has noted that the "use of antibiotics in food-producing animals allows antibiotic-resistant bacteria to thrive while susceptible bacteria are suppressed or die." Warning that "much of antibiotic use in animals is unnecessary and inappropriate and makes everyone less safe," the report highlights CDC’s work with the Food and Drug Administration and U.S. Department of Agriculture to monitor trends in antibiotic resistance "among enteric bacteria from humans, retail meats, and food-producing animals." It also recommends that antibiotics only be used in food-producing animals "to manage and treat infectious diseases, not to promote growth."

"Perhaps the most important action needed to greatly slow down the development and spread of antibiotic-resistant infections is to change the way antibiotics are used," concludes the report, which estimates that at least 23,000 people die each year from antibiotic-resistant infections. "Stopping even some of the inappropriate and unnecessary use of antibiotics in people and animals would help greatly in slowing down the spread of resistant bacteria."

In a related development, a recent study has reportedly concluded that "the contributions of local animal populations to human drug-resistant Salmonella may previously have been overstated." A. E. Mather, et al., "Distinguishable Epidemics of Multidrug-Resistant Salmonella Typhimurium DT104 in Different Hosts," Science, September 2013. According to a recent press release, researchers with the Wellcome Trust Sanger Institute analyzed the genomes of 373 Salmonella Typhimurium samples taken from humans and animals, not only finding that the bacteria populations in these two hosts were distinguishable, but that humans tended to acquire infections from other humans while harboring a greater diversity of drug resistance.

"For the first time, we’ve determined in detail and on a large scale how Salmonella strains taken from humans and animals in the same setting and over the same time period relate to each other," explained the lead author. "Our genomic data reveal how the Salmonella bacteria spread during the course of a long-term epidemic. We found that people have a more diverse source of infection and antibiotic resistance than just the local animals, pointing towards alternative sources." See Wellcome Trust Sanger Institute Press Release, September 12, 2013.