Tools for Tracking Antibiotic Resistance
When a team of researchers from Sweden first started measuring chemicals in a river near Patancheru, India, they found shocking concentrations of drugs flowing downstream--for example, levels of the potent antibiotic ciprofloxacin greater than those found in the blood of humans taking the drug. A major source of these drugs was treated wastewater from pharmaceutical manufacturing plants that was discharged into the river and surrounding environs, as Joakim Larsson and his colleagues from the University of Gothenburg reported several years ago.(1) An update published in PLoS ONE2 now links the drugs with downstream development of microbes with genetic resistance to multiple antibiotics typically used to treat human illness.
The researchers found snippets of genetic material in bacteria from river sediments downstream of the treatment plant that confetted resistance not only to ciprofloxacin, a fluoroquinolone, but also to betalactams, aminoglycosides, sulfonamides, and other classes of antibiotics. Several genes that provide resistance to ciprofloxacin and have the ability to transfer between different bacteria were extremely common at some of the sampling sites. (2)
What if the bacteria in Patancheru could develop ways to survive the daily onslaught of ciprofloxacin, most likely over the course of years in their river environment, and ended up passing on their new genetic resistance to pathogenic bacteria that could be a threat to human health? Although Larsson's team has yet to catalog antibiotic resistance in the local population, people in the region are continually exposed to resistant microbes as they use the river water for agriculture and everyday home life. "This is a huge scary experiment in nature," Larsson says.
Just how isolated these kinds of drug "hot spots" are remains unknown, although researchers have pressed for global monitoring of antibiotic use and resistance for the past several decades, across disciplines as diverse as clinical medicine and ecotoxicity. Bringing together these fields reflects the breadth of challenges in tracking antibiotic resistance, but new technologies and ideas hold promise for the near future.
Overcoming a Lack of Coordination
"Misuse of antibiotics is obviously what creates the basic factors that produce drug resistance," says Mario Raviglione, director of the World Health Organization (WHO) department charged with tuberculosis control; this is true in both the developing and developed worlds. And despite educational campaigns by the U.S. Centers for Disease Control and Prevention (CDC) (3) and others aimed at improving clinicians' use of antibiotics, overprescribing remains a problem for multiple reasons. (4) Moreover, patient compliance--for example, taking the full course of prescribed antibiotics--can be lax, which leads to the evolution of more antibiotic-resistant pathogens.
Agricultural use of human drugs adds to the threat of drug resistance. After World War II, antibiotics started to be used for purposes such as growth promotion in livestock. Since then, antibiotics--and in some cases, the genes for resistance to multiple drugs--have been found on industrial cattle, swine, and shrimp farms, (5), (6), (7), (8), measured on chicken skins in grocery stores, (9) and even detected in apple orchards sprayed with drugs originally intended for human use. (10)
For World Health Day in April 2011 the WHO chose the theme of the global spread of antibiotic resistance, marking a little over a decade since the organization first called for patient and doctor guidelines to protect antibiotics from becoming obsolete. (11) A document issued by the WHO in 2001 put forth a series of recommendations for patients and the general community, prescribers and dispensers, hospitals, agricultural enterprises, national governments and health systems, and drug developers and promoters. (12) However, in general "very few countries, if any, have made a comprehensive effort to do any of the measures included in the older guidelines," says Raviglione, who led preparations for World Health Day 2011. …