Ligase chain reaction (LCR)
Abbott Laboratories, Abbott Park, III
Through the process, probe DNA is amplified to a level readily detectable using assays similar to those described for the biotin-avidin system. One commercial system (Abbott Laboratories, Abbott Park, 111) uses an LCR approach to deted Chlamydia trachomatis and Neisseria gonorrhoeae in urine or other specimens.
Rather than amplifying the probe, the signal used to detect hybridization between the amplicon and probe can be amplified by increasing the number of reporter molecules per probe. This is accomplished by attaching multiple signal-generating molecules to the probe that recognizes the target DNA. Thus, several reporter molecules are associated with each probe-target duplex. The potential of this approach is exemplified by the development of branched probes. These probes are complex nucleic acid constructions involving capture probes, extender probes, and multicopy DNA sequences that can accommodate thousands of reporter molecules per probe-target duplex. This method for detecting target nucleic acid is exquisitely sensitive.
A number of other non-PCR-based technologies have been successfully used to detect a variety of infectious agents (Thble 8-3). As with PCR, these applications are able to amplify DNA, RNA, mRNA, and rRNA targets; to have multiplex capabilities; and to be qualitative or quantitative. To learn more about these alternative target amplification methods, refer to additional reading and articles authored by Ginocchio.
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