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Clinical and Diagnostic Laboratory Immunology, March 2000, p. 258-264, Vol. 7, No. 2
VA Medical Center and Department of Medicine,
University of Minnesota, Minneapolis, Minnesota
Received 12 July 1999/Returned for modification 5 November
1999/Accepted 24 November 1999
Modified thermal cycling conditions were explored in an effort to
improve the reproducibility and resolving power of repetitive-element PCR (rep-PCR) fingerprinting. Assay performance was rigorously evaluated under standard and modified cycling conditions, using as a
test set 12 strains putatively representing 12 serovars of Salmonella enterica. For all three fingerprint types
(ERIC2, BOXA1R, and composite fingerprints), the use of extremely
elevated annealing temperatures plus an initial "touchdown" cycling
routine yielded significant improvements in day-to-day reproducibility
and discriminating power despite the somewhat sparser appearance of the
fingerprints. Modified cycling conditions markedly reduced the
variability of fingerprints between cyclers, allowing fingerprints from
different cyclers to be analyzed together without the degradation of
assay performance that occurred with between-cycler analyses under
standard cycling conditions. With modified cycling, composite
fingerprints exhibited the lowest reproducibility but the highest net
discriminating power of the three fingerprint types. rep-PCR
fingerprints led to the discovery of a serotyping error involving one
of the 12 test strains. These data demonstrate that modified cycling
regimens that incorporate elevated annealing temperatures (with or
without an initial touchdown routine) may markedly improve the
performance of rep-PCR fingerprinting as a bacterial typing tool.
1071-412X/00/$04.00+0
Improved Repetitive-Element PCR Fingerprinting of
Salmonella enterica with the Use of Extremely Elevated
Annealing Temperatures
*
Corresponding author. Mailing address: Infectious
Diseases (111F), VA Medical Center, One Veterans Dr.,
Minneapolis, MN 55417. Phone: (612) 725-2000, ext. 4185. Fax: (612)
725-2273. E-mail: johns007{at}.tc.umn.edu.
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