CLINICAL CASES
59
§:
5
3
'
5
'
s*
Dénaturation and
^
annealing of the primers
^
Primers elongation
Figure 6-1. PCR reaction diagram.
PCR is also becoming the leading method for detection of the continuously
increasing number of human pathogens. Examples include herpes simplex
virus (HSV), human papillomavirus, human immunodeficiency virus (HIV),
human T lymphotropic virus type I and type II, cytomegalovirus (CMV),
Epstein-Barr virus, human herpesvirus-6 (HHV-6), hepatitis B virus, B16 par-
vovirus, JC and BK viruses, rubella virus, mycobacteria,
Toxoplasmosis gondii,
Trypanosoma cruzi,
and malaria, with many more to follow. PCR can be applied
as a detection method for virtually any pathogen for which even limited nucleotide
sequence information is known and for which a specimen of infected tissue
can be readily obtained. In most cases PCR assays are more discriminative
than conventional serology. For example, it is difficult to distinguish HSV-I
from HSV-II or HIV-1 from HIV-2 by serology, yet such distinctions can be
readily made on the basis of PCR amplification of type-specific genetic
sequences. PCR yields rapid results, typically in 1 to 2 days in a clinical setting.
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