Advanced Techniques in Diagnostic Microbiology

162 H. Li and Y-W. Tang
Currently, two diagnostic companies have their signal amplification products
available for diagnostic microbiology purposes. The Digene hybrid capture system
is widely used to determine human papillomavirus (HPV) infection and viral types
in cervical swabs or fresh cervical biopsy specimens as well as other diagnostic
targets (Brown et al., 1993). Persistent high-risk human papillomavirus infection
detected by the System represents a reliable tool to select populations at risk for the
development of high-grade cervical lesions (Brown et al., 1993; Schiffman et al.,
1995). Besides HPV, Hybrid capture assays for the detection of hepatitis B virus,
cytomegalovirus, C. trachomatis, and N. gonorrhoeae in clinical specimens are
commercially available (Ho et al., 1999; Mazzulli et al., 1999; Schachter et al.,
1999).
Another signal amplification-based product is the branched DNA (bDNA) probe
developed and manufactured by Chiron Corp., which uses multiple specific synthetic
oligonucleotides hybridize to the target and capture the target onto a solid
surface (Urdea et al., 1991). Synthetic bDNA amplifier molecules, which are
enzyme conjugated, branched oligonucleotide probes, are added. Hybridization
proceeds between the amplifier and the immobilized hybrids. After addition of
a chemiluminescent substrate, light emission is measured and may be quantified.
This technique represents an excellent method for quantitation and therapeutic
response monitoring of HCV and HIV-1 (Lau et al., 1993; Revets et al.,
1996).
Current commonly used in vitro NAA techniques are categorized and summarized
in Table 10.1. Each of the three categories is discussed in the following several
chapters of this book, and the discussion is followed by a closer look at individual
techniques including principles and applications in diagnostic microbiology.
References
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