THIRD WORLD NETWORK BIOSAFETY INFORMATION SERVICE
Scientists have published a paper in the journal Environmental Science & Technology documenting the presence of antibiotic-selectable synthetic plasmid vectors in microbes from six Chinese rivers. These antibiotic resistance genes are routinely used in molecular biology and genetic engineering experiments.
Heavy use of antibiotics in hospitals and on farms has polluted the environment with bacteria carrying genes that confer resistance to the drugs. Once in the environment, the microbes can quickly transfer the genes to other bacteria, leading to antibiotic-resistant strains that can cause severe and sometimes untreatable infections.
This study provides definitive evidence that genetic constructs from the lab have reached the environment, compounding the situation of antibiotic resistance further. The authors say that while the study reveals environmental contamination of the synthetic antibiotic resistance genes, it also suggests that synthetic plasmid vectors may represent a source of antibiotic resistance in humans.
If genetic engineering lab experiments are to be conducted, they must be done under strictly contained conditions. It must be ensured that transgenes and synthetic genes do not reach the environment. Because of the concerns that the use of GM crops containing antibiotic resistance marker genes could compromise medical treatments due to the transfer of these genes to gut or soil bacteria, some jurisdictions have identified and phased out particular antibiotic resistance marker genes, and/or banned GM food and feed products containing antibiotic resistance marker genes.
In any case, the issue of antibiotic resistance genes should be taken into particular consideration when conducting risk assessment of GMOs containing such genes. Countries can and should subject GMOs destined for contained use to risk assessments and set standards for contained use within their jurisdiction, rights which the Cartagena Protocol on Biosafety recognizes.
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Item 1
http://www.ncbi.nlm.nih.gov/pubmed/23215020
Environ Sci Technol. 2012 Dec 18;46(24):13448-54. doi: 10.1021/es302760s. Epub 2012 Dec 6.
A survey of drug resistance bla genes originating from synthetic plasmid vectors in six Chinese rivers.
Chen J, Jin M, Qiu ZG, Guo C, Chen ZL, Shen ZQ, Wang XW, Li JW.
Source
College of Life Sciences, Sichuan University, Chengdu, Sichuan Province 610064, People’s Republic of China.
Abstract
Antibiotic resistance poses a significant challenge to human health and its rate continues to rise globally. While antibiotic-selectable synthetic plasmid vectors have proved invaluable tools of genetic engineering, this class of artificial recombinant DNA sequences with high expression of antibiotic resistance genes presents an unknown risk beyond the laboratory setting. Contamination of environmental microbes with synthetic plasmid vector-sourced antibiotic resistance genes may represent a yet unrecognized source of antibiotic resistance. In this study, PCR and real-time quantitative PCR were used to investigate the synthetic plasmid vector-originated ampicillin resistance gene, ?-lactam antibiotic (blá), in microbes from six Chinese rivers with significant human interactions. Various levels of blá were detected in all six rivers, with the highest levels in the Pearl and Haihe rivers. To validate the blá pollution, environmental plasmids in the river samples were captured by the E. coli transformants from the community plasmid metagenome. The resultant plasmid library of 205 ampicillin-resistant E. coli (transformants) showed a blá-positive rate of 27.3% by PCR. Sequencing results confirmed the synthetic plasmid vector sources. In addition, results of the Kirby-Bauer disc-diffusion test reinforced the ampicillin-resistant functions of the environmental plasmids. The resistance spectrum of transformants from the Pearl and Haihe rivers, in particular, had expanded to the third- and fourth-generation of cephalosporin drugs, while that of other transformants mainly involved first- and second-generation cephalosporins. This study not only reveals environmental contamination of synthetic plasmid vector-sourced blá drug resistance genes in Chinese rivers, but also suggests that synthetic plasmid vectors may represent a source of antibiotic resistance in humans.
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Item 2
Labs could contaminate rivers with antibiotic resistance genes
By Deirdre Lockwood
Chemical & Engineering News, USA
17 January 2013
http://cen.acs.org/articles/90/web/2012/12/Labs-Contaminate-Rivers-Antibiotic-Resistance.html
Environment: Researchers find evidence of antibiotic resistance genes used in molecular biology experiments in Chinese rivers
Researchers report that antibiotic resistance genes used in molecular biology and genetic engineering experiments may have reached the environment. In six Chinese rivers, researchers found bacterial DNA carrying these synthetic genes (Environ. Sci. Technol., DOI: 10.1021/es302760s). Still experts call for more studies to confirm the results and pinpoint specific sources of the genes.
Heavy use of antibiotics in hospitals and on farms has polluted the environment with bacteria carrying genes that confer resistance to the drugs. Once in the environment, the microbes can quickly transfer the genes to other bacteria, leading to antibiotic-resistant strains that can cause severe and sometimes untreatable infections.
But these resistance genes also are cheap, powerful tools for biologists. In so-called molecular cloning studies, researchers introduce the genes into synthetic versions of plasmids, which are small, circular molecules of DNA found in bacteria. The synthetic plasmids also include another gene that the scientists want to study. By treating the bacteria with the antibiotic, the researchers can ensure that the microbes that survive contain both the resistance gene and their gene of choice.
To make sure that the plasmids don’t escape the lab, academic institutions in the U.S. follow special procedures to treat waste from the experiments before disposing of it: They kill any remaining microbes with high heat and sometimes then incinerate the waste.
Industrial scientists have also used molecular cloning to engineer crops and bacteria for biofuel production and environmental remediation. To prevent the spread of antibiotic resistance, however, most genetically modified crops are now produced without these genes.
But because this technique is still commonly used in molecular biology labs, some researchers have been concerned that these experiments could release resistance genes into the environment. To search for antibiotic-resistance genes introduced by synthetic plasmids, Jun-Wen Li at the Institute of Health and Environmental Medicine, in Tianjin, China, and his colleagues took water samples from six Chinese rivers downstream of densely populated cities. They extracted plasmids from the samples and transferred the DNA into Escherichia coli. Then they screened the bacteria for a gene commonly used in academic and industrial labs that confers resistance to the antibiotic ampicillin. To determine if a gene in a sample came from a manmade source, they used polymerase chain reaction to look for sequences unique to several synthetic plasmids.
The researchers found synthetic resistance genes in all six rivers. Of all of the ampicillin-resistance plasmids they found in the rivers, about 27% had the synthetic vector-sourced gene.
Justin J. Donato, a biochemist at the University of St. Thomas, in St. Paul, Minn., says the study provides the first definitive evidence that genetic constructs from the lab have reached the environment. Given that no one previously had reported observing these synthetic plasmids in the environment, Donato is surprised by how prevalent they are. He says the study requires replication especially to rule out the possibility of sample contamination from plasmids already in Li’s laboratory.
Anders Janzon, a postdoctoral fellow in microbiology at Cornell University, is also cautious about how to interpret the study’s findings. He hopes subsequent studies will investigate pristine environments to ensure that the synthetic plasmid sequences don’t already exist there.
"If future studies support these findings, this will be a concern that scientists will have to seriously address during the design and implementation of their experiments," Donato says.