the unique RET mutations was not possible when the derivative curves overlapped. Although not all pathogenic RET mutations were available for analysis, a recent systematic study of high-resolution melting detection of heterozygous point mutations within a PCR amplicon found a sensitivity and specificity of 100% for amplicons Ͻ400 bp in size (15 ). High-resolution melting analysis for mutation scanning is a rapid (1-2 min after PCR), costeffective assay that requires no processing or separation steps. As applied to RET mutation scanning, accuracy of heterozygote detection appears to be 100%, and some (but not all) sequence variations can be distinguished from each other. Because samples are immediately available for further processing after high-resolution melting analysis, the detected variant samples can be sequenced for confirmation of genotype.

Abstract. We investigated the use of a TaqMan 5Ј nuclease assay (5NA) directed against the Francisella tularensis outer membrane protein (Fop) gene and a polymerase chain reaction-enzyme immunoassay (PCR-EIA) directed against the tul 4 gene for detection of this organism in experimentally infected mice and in field-collected tick vectors. We also evaluated the use of specially formulated filter paper (FTA) for rapid sample preparation. The 5NA had a detection limit of 1 pg of genomic DNA (Ͻ100 colony-forming units) and could be completed within several hours. The PCR-EIA could detect 1 pg of genomic DNA and 10 attograms (ag) (22 copies) of cloned insert, but takes longer to perform. Both assays were genus-specific, and successfully detected F. tularensis in mouse tissues (5NA) and in tick extracts (PCR-EIA). The FTA paper provided inexpensive, rapid, template preparation for the tick extracts, mouse tissues, and DNA obtained from clinical specimens. These probe-based assays have the potential to provide rapid, real-time/high-throughput molecular diagnostics in field situations.

The 5′ nuclease PCR assay uses a fluorescently labeled oligonucleotide probe (TaqMan) to rapidly detect and quantitate DNA templates in clinical samples. We developed a 5′ nuclease PCR assay targeting the plasminogen activator gene (pla) ofYersinia pestis. The assay is species specific, with a detection threshold of 2.1 × 105 copies of thepla target or 1.6 pg of total cell DNA. The assay detectedY. pestis in experimentally infected Xenopsylla cheopis fleas and in experimentally infected monkey blood and oropharyngeal swabs. The TaqMan assay is simple to perform and rapid and shows promise as a future field-adaptable technique.

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