Berlin Highlights—Antimicrobial Resistance in the Environment
Mark Montforts, Satoru Suzuki, Marko Virta, and Patricia Keen
As we look towards securing a sustainable future, two sessions at the SETAC Europe 22nd Annual Meeting brought together key people concerned with the science and policy of antibiotic resistance in the environment. The morning represented the union of two independently proposed sessions focused on a common theme: the role of the environment in human health and ecosystem health consequences resulting from the development of antibiotic resistance. Examples of an ever-growing body of evidence that underlines the importance of the environment in extending opportunities for selective pressure for resistance in important bacteria species were described in 12 platform presentations and 28 posters. Health issues associated with environmental dissemination of antimicrobial resistance in critical species of bacteria have now earned global attention in the scientific community – only a few years ago, a dozen abstracts would be submitted to a session dedicated to the topic but now, the total number of abstracts for the 2012 session has more than quadrupled.
The development and dissemination of bacterial resistance to antibiotics used in human medicine is a crucially important public health issue but is not restricted to clinical settings. The overwhelming evidence is that environmental organisms harbor a previously underappreciated density of antibiotic resistance genes, but only a fraction has been identified in pathogens and other bacteria. Proliferation of new resistance traits is an ongoing process, as is the continuous introduction of large numbers of antimicrobial-resistant (AMR) organisms into the environment together with both nutrients (waste) and stressors (antibiotics, metals, disinfectants).
People came from far regions of the world to the Thursday morning sessions with the common goal to share and learn the current knowledge concerning risks associated with antibiotics and antimicrobial resistance genes as environmental contaminants. With a diverse blend of disciplines represented including civil engineering, clinical microbiology, environmental chemistry, veterinary medicine and molecular ecology, papers discussed key elements of fate and effects of antibiotic resistant bacteria and genetic determinants of antimicrobial resistance in the environment. From Switzerland, we learned that despite use of streptomycin to treat fire blight in apple orchards, quantitative polymerase chain reaction (qPCR) measurement of selected resistance genes indicated that these levels were relatively low in apples at harvest. Research from Seattle, Washington has demonstrated that up to 50% of isolates of MRSA (frequently termed “Superbug”) collected from beaches and some high-touch public surfaces were not of human origin whereas isolates from student homes or community spaces were all human origin. Research conducted near fish cages in the Philippines and near aquaculture facilities in the Baltic Sea used molecular methods to determine that selected antibiotic resistance genes are higher in sediment under fish pens than in sediments collected from pristine sites. People with a shared interest in antimicrobial resistance in the environment gained information, inspiration and new friends.
As with all SETAC meetings, new scientific knowledge was the most important currency exchanged in platform sessions, poster presentations and over coffee. Antibiotics and antimicrobial resistance genes are now accepted as emerging contaminants in the environment that merit further scientific exploration. Antibiotic resistance of veterinary drugs have been identified as priority public health concerns in Germany, the Netherlands and several other nations. A number of the studies that investigated the occurrence of antimicrobial resistance from sources such as wastewater treatment plants, agricultural run-off from fertilized fields and aquaculture facilities found that certain antibiotic resistance genes can be elevated in the environment and disseminated through various environmental compartments. Molecular methods, specifically qPCR analyses, are now frequently used to estimate abundance of several antibiotic resistance genes and integrons in environmental samples. Studies with maize and other plants suggest that the root rhizosphere is an important hotspot for microbial activity that can lead to antimicrobial resistance in bacteria. Selection for antibiotic resistance in critical species of bacteria can result not only from exposure to antibiotic compounds but also from exposure to metals such as copper, zinc or mercury.
Regulatory action is developing within the EU and the USA, aligning research (www.cost-dare.eu) and regulatory instruments, while research from the UK demonstrated that the current exposure-based trigger value for veterinary medicines fails to protect against AMR. Indeed, very low concentrations of antibiotics should be evaluated against criteria such as selection, changing community structures and environmental risk. It should be investigated how "environmental" and "anthropogenic" compartments connect, not only to understand how resistance disperses from environment to humans, but also to see if resistance that is emitted into the environment as pollutants, might facilitate the environmental adaptation of pathogens, or alter the natural ecological adaptation of environmental organisms. Tools and approaches developed for ecotoxicology may be useful to understand the risk of resistance in clinical settings and vice versa. As Glasgow beckons, we look forward to next year’s session to expand our knowledge of health and environmental risks associated with antimicrobial resistance in the environment.
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