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Appl. Environ. Microbiol., Oct 1995, 3724-3728, Vol 61, No. 10
HA Bassler, SJ Flood, KJ Livak, J Marmaro, R Knorr and CA Batt
A PCR-based assay for Listeria monocytogenes that uses the hydrolysis of an
internal fluorogenic probe to monitor the amplification of the target has
been formatted. The fluorogenic 5' nuclease PCR assay takes advantage of
the endogenous 5' --> 3' nuclease activity of Taq DNA polymerase to
digest a probe which is labelled with two fluorescent dyes and hybridizes
to the amplicon during PCR. When the probe is intact, the two fluorophores
interact such that the emission of the reporter dye is quenched. During
amplification, the probe is hydrolyzed, relieving the quenching of the
reporter and resulting in an increase in its fluorescence intensity. This
change in reporter dye fluorescence is quantitative for the amount of PCR
product and, under appropriate conditions, for the amount of template. We
have applied the fluorogenic 5' nuclease PCR assay to detect L.
monocytogenes, using an 858-bp amplicon of hemolysin (hlyA) as the target.
Maximum sensitivity was achieved by evaluating various fluorogenic probes
and then optimizing the assay components and cycling parameters. With crude
cell lysates, the total assay could be completed in 3 h with a detection
limit of approximately 50 CFU. Quantification was linear over a range of 5
x 10(1) to 5 x 10(5) CFU.
Copyright © 1995, American Society for Microbiology
Use of a fluorogenic probe in a PCR-based assay for the detection of Listeria monocytogenes
Department of Food Science, Cornell University, Ithaca, New York 14853, USA.
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