Nucleic acid approaches to toxin detection

Chatwell, Nicola (2013) Nucleic acid approaches to toxin detection. MPhil thesis, University of Nottingham.

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PCR is commonly used for detecting contamination of foods by toxigenic bacteria. However, it is unknown whether it is suitable for detecting toxins in samples which are unlikely to contain bacterial cells, such as purified biological weapons. Quantitative real-time PCR assays were developed for amplification of the genes encoding Clostridium botulinum neurotoxins A to F, Staphylococcal enteroxin B (SEB), ricin, and C. perfringens alpha toxin. Botulinum neurotoxins, alpha toxin, ricin and V antigen from Yersinia pestis were purified at Dstl using methods including precipitation, ion exchange, FPLC, affinity chromatography and gel filtration. Additionally, toxin samples of unknown purity were purchased from a commercial supplier. Q-PCR analysis showed that DNA was present in crudely prepared toxin samples. However, the majority of purified or commercially produced toxins were not detectable by PCR. Therefore, it is unlikely that PCR will serve as a primary toxin detection method in future.

Immuno-PCR was investigated as an alternative, more direct method of toxin detection. Several iterations of the method were investigated, each using a different way of labelling the secondary antibody with DNA. It was discovered that the way in which antibodies are labelled with DNA is crucial to the success of the method, as the DNA concentration must be optimised in order to fully take advantage of signal amplification without causing excessive background noise. In general terms immuno-PCR was demonstrated to offer increased sensitivity over conventional ELISA, once fully optimised, making it particularly useful for biological weapons analysis.

Finally, genetic methods for the differentiation of toxigenic Ricinus communis strains were examined, including SSR, RAPD, RFLP and SNP analysis using next generation sequencing. The results showed that the species has low genetic diversity, making genotyping a particularly difficult task, however SSR analysis was able to provide a degree of differentiation and 454 Sequencing™ identified six SNP targets that warrant further investigation in future.

Item Type: Thesis (University of Nottingham only) (MPhil)
Supervisors: Dodd, C.E.R.
Hill, P.J.
Subjects: Q Science > QP Physiology > QP501 Animal biochemistry
Faculties/Schools: UK Campuses > Faculty of Science > School of Biosciences
Item ID: 13666
Depositing User: EP, Services
Date Deposited: 24 Feb 2014 09:57
Last Modified: 15 Sep 2016 13:43

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