On 15 January, four major UK supermarkets withdrew meat-based products in the light of the Food Standards Agency Ireland (FSAI) findings into the contamination of beef with horse and other animal meats.
The highest content of equine DNA was 29% in one sample, with the vast majority of others tested below <0.2%. Many samples were also found to contain porcine DNA.
The scandal has resulted in one of the biggest food recalls in UK history, and multiple suppliers across the EU being implicated. To deal with the growing scandal over mislabelled horse-meat, the EU Health Commissioner today urged all members to carry out DNA tests on processed beef for traces of horse-meat for three months from 1 March. Furthermore, tests for the presence of the veterinary medicine phenylbutazone ("bute") were recommended.
We thought it may be interesting to look at some of the scientific challenges in authenticating presence of animal species in our meat. What types of horse-meat tests are out there? Further, how accurate are current tests in quantifying horse DNA? In fact, one food testing company in the UK this week has urged the food testing industry to not rush into horse DNA testing due to issues surrounding DNA quantification.
Currently, in the food testing industry there exist two main types of assays for detecting horse meat in beef – either protein-based or DNA-based.
The ELISA method tests for protein and has a 1-2% detection limit. Separate kits exist for testing either raw or cooked meat. However, due to the contamination being largely unknown, the ELISA method could possibly show inaccurate results.
With molecular-based testing of equine DNA using PCR, the detection limit is 1% but the limit of detection (i.e. sensitivity) can go down even lower. Both real-time PCR methods and end-point PCR (with subsequent RFLP analysis or sequencing) are suitable for DNA testing of equine DNA. PCR based methods amplify sequences from mitochondrial DNA (mtDNA) which is more highly conserved and widely found in animal species than nuclear DNA. Specific details of primer sequences are not always made available by different companies.
Due to the wide variation in the amount of mitochondria from cell to cell in different tissue types (varying from 1 mitochondria per cell to 1000’s), it is not possible to accurately quantify the amount of horse DNA in a sample. DNA testing therefore should be seen as being qualitative rather than quantitative, and limitations to their accuracy should be borne in mind when interpreting results or those quoted in the press.
Bioline high performance molecular biology products have been cited in recent papers investigating contamination of meat products by horse meat, as well as other types of contaminants detected in food-testing.
Useful further reading:
Australia Day traditionally marks the anniversary in 1788, when Captain Arthur Philip and the First Fleet arrived at Port Jackson, now part of Sydney, New South Wales, to establish the first European settlement. The holiday is an opportunity for Australians to celebrate the founding of the country and its culture.
Bioline is also privileged to call Sydney home. For 10 years, Bioline Australia has been proud to be a primary manufacturer and supplier of best-in-class molecular biology tools to the leading research universities and institutes in Australia. Bioline's new R&D facility in the Australian Technology Park in Sydney was officially opened by the Hon. Verity Firth MP (Minister for Science and Medical Research) in November 2007. For those interested, photos from the launch are available here.
We thought the Australia Day celebrations might be a good time to highlight some of the scientific achievements of our antipodean cousins, so this month's Bioline Scholar features a selection of interesting, recently published papers from scientists 'down under'.
Blyton M.D. et al. (2013). High temporal variability in commensal Escherichia coli strain communities of an herbivorous marsupial. Environ. Microbiol. doi: 10.1111/1462-2920.12088
In this study from The Australian National University in Canberra, commensal E. coli strains of mountain brushtail possums were quantified at both the host population level and within individuals. E. coli strains were identified using rep-PCR profiling and quadruplex PCR. A high level of temporal variability was found.
Luter, H.M. et al. (2012). Thermal and sedimentation stress are unlikely causes of brown spot syndrome in the coral reef sponge, Ianthella basta. PLoS ONE 7(6): e39779.
Brown spot lesions currently affect a large population of I. basta, an ecologically important sponge species on the Great Barrier Reef. Researchers from the Australian Institute of Marine Science at James Cook University found changes in the microbial community of I. basta to be stable. Thermal and sedimentation stress were not likely to be responsible for the syndrome.
Kelly, R.D. et al. (2013). Mitochondrial DNA haplotypes define gene expression patterns in pluripotent and differentiating embryonic stem cells. Stem Cells doi: 10.1002/stem.1313
In this paper from the Monash Institute of Medical Research in Melbourne, the effects of different mitochondrial DNA haplotypes on differentiation and development were studied using embryonic stem cell lines. In conclusion, mitochondrial DNA haplotypes play a pivotal role in the process of differentiation and mediate cell fate.
Roberts, T. et al. (2013). Subtype distribution of Blastocystis isolates from a variety of animals from New South Wales, Australia. Vet. Parasit. doi: 10.1016/j.vetpar.2013.01.011
Researchers from St Vincent's Hospital and the University of Technology, Sydney identified nine different genetic subtypes of Blastocytis, a genus of Protozoan parasite, in different animal species in NSW. Blastocystis was identified for the first-time from the eastern grey kangaroo, red kangaroo, wallaroo, snow leopard and ostrich. Further investigation into the genetic diversity of Blastocystis may help identify the zoonotic potential of Blastocystis.
Covelloa, J.M. et al. (2013). Isolation of RAG-1 and IgM transcripts from the striped trumpeter (Latris lineata), and their expression as markers for development of the adaptive immune response. Fish Shellfish Immun. doi: 10.1016/j.fsi.2012.12.015
In this work from the National Centre for Marine Conservation and Resource Sustainability, University of Tasmania, mRNA sequences from the RAG-1 and IgM heavy chain were analysed from the striped trumpeter (Latris lineata). The expression of the two genes was assessed throughout the early developmental stages of striped trumpeter larvae and used as markers to follow the ontogeny of the adaptive immune response.
That's it for this edition of Bioline Scholar! If you have published research using Bioline products, then get in touch, tell us and your paper could make it into a future edition of Bioline Scholar.