10. Antibiotic resistance

For medical professionals around the world, antibiotic-resistant bacteria are fast becoming a serious problem. In some hospitals the common pathogen Staphylococcus aureus is resistant to almost all known antibiotics.(1) The main causes suspected for the build-up of resistant bacteria are the overuse of antibiotics in medicine and animal feed. A study from East Germany demonstrates the speed at which resistance can spread:

In 1982, the antibiotic streptothricin began to be administered to pigs. By 1983, plasmids resistant to streptothricin were found in the pigs' gut bacteria. This resistance had spread to the gut bacteria of farm workers and their family members by 1984, and to the general public and pathogenic strains of bacteria the following year. The antibiotic was withdrawn in 1990, yet the prevalence of the resistant bacteria remained high when monitored in 1993.(2)

The marker genes used in genetic engineering confer resistance to antibiotics commonly used in human and veterinary medicine. Some scientists believe that eating GE food containing these marker genes could encourage gut bacteria or oral bacteria to develop antibiotic resistance.

• In 1996, the Advisory Committee on Novel Foods and Processes advised the UK government to vote against an authorisation being sought by Novartis (now Syngenta) for a GE maize containing a marker gene resistant to ampicillin. They felt that the presence of this intact marker gene, together with a bacterial promoter gene that would enable it to operate in bacteria, posed an unacceptable risk.(3)
  
  
• A study published in 1999 indicates that oral bacteria could pick up DNA released from food or other bacteria within the mouth.(4)

• In one experiment, genetically engineered rape, black mustard, thorn-apple and sweet peas all containing antibiotic-resistant genes were grown together in the laboratory with the fungus Aspergillus niger. In some cases their leaves were added to the soil. In each of the experiments, the genes for antibiotic resistance ended up being transferred to the fungus.(5)

References

1. 7th Report of the House of Lords Select Committee on Science and Technology (1998) Resistance to Antibiotics and other Antimicrobial Agents.
2. Tschäpe H. (1994) The spread of plasmids as a function of bacterial adaptability. FEMS Microbiology Ecology 15:23-32;
Ho M-W., Traavik T., Olsvik O., Tappeser B., Howard V., Weizsacker C., McGavin G. (1998) Gene Technology and Gene Ecology of Infectious Diseases. Microbial Ecology in Health and Disease, 10: 33-59
3. AgBiotech, News and Information 8 (9): 159N.
4. Mercer D., Scott K., Bruce-Johnson A., Glover L. and Flint H. (1999) Fate of Free DNA and Transformation of the Oral Bacterium Streptococcus gordonii DL1 by Plasmid DNA in Human Saliva. Applied and Environmental Microbiology, Vol 65, No. 1, p 6-10)
5. Hoffmann T., Golz C. and Schieder O. (1994) Foreign DNA sequences are received by a wild-type strain of Aspergillus niger after co-culture with transgenic higher plants. Current genetics 27: 70-76.
 

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