Assays based on nucleic acid detection have the potential
for greater sensitivity than immunological assays. For example,
Wilson et al. recently described an assay for bacteremia
which was based on signal amplification by Q-beta replicase
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and which allowed the detection of 10 CFU of Escherichia
coli per sample (40). The PCR has been applied, in numerous
reports (38), to the detection and identification of specific
bacterial pathogens. In many cases, the target genes are
those known to be involved in the pathogenicity or virulence
of the pathogen (15, 30). For example, Kuritza and Oehler
described the use of a protease A gene for the detection of a
specific bacterial species causing meningitis, Neisseria meningitidis
(19). In other cases, the target is a random sequence
cloned from a genomic library and selected by differential
hybridization to the pathogen and its close relatives (35).
Mahbubani et al. described a system for the detection of
Legionella pneumophila and Legionella species with two
sets of PCR primers in a multiplex reaction (25).