Advangates of simultaneously targeting multiple VMGs include the following:
(i) Specificity is the key attribute that is achieved by using the VMGs. Using multiple probes per amplicon or gene, we have achieved close to 100% specificity implying we do not make a call for presence or absence unless some 20 to 100 probes indicate positive or negative signals, respectively. Because the method exploits VMGs, it will also be capable of detecting organisms that may have been intentionally altered to become pathogens.
(ii) Accuracy has been assesed at both the probe and the gene level. At the gene level, the accuracy of our existing hybridization-based chips is close to 100%. In all the hybridizations carried out so far, we never observed a false positive signal implying the presence of a target gene or a false negative signal implying the absence of a gene when it was present.
(iii) Limit of Detection (LOD) and Limit of Quantification (LOQ). We have established the limit of detection and limit of quantification of our method at several levels from cells present in various environmental sample matrices to number of copies added to a known amount of genomic DNA as background. The limit of detection for our current DNA biochip is close to 0.001% of the target gene. This value reflects the detection limit obtained when 12 pathogens are simultaneously spiked and detected in a parallel fashion. A lower detection limit can be achieved when only a limited number of pathogens are present and targeted.
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