89
outbreaks and the establishment of control measures in a timelymanner;
3) in view of providing only the search of L. pneumophila serogroup
1 (despite of the higher prevalence of the serogroup 1),omitted cases of
Legionellosiscan reach 40%; 4)detection from the third day of the onset of
the symptoms that can persist for more than 300 days; 5) sensitivity in 80%
and specificity in 97%.
6.1.6 Detection of nucleic acid of
Legionella
The polymerase chain reaction (PCR) represents one of the fewdiagnostic
tests available with potential to detect all the known species of
Legionella
.
However, the following limitations are mentioned:
1 - The post-amplification procedures are difficult and can cause
contamination by transportation thus generating false positive results.
2 - The validation and the availability of the tests for clinical use are
limited.
The detection of genetic material of L. pneumophila in expectoration,
in urine or in blood based on PCR techniques, is being used satisfactorily in
reference and investigation laboratories.
Since most of the rapid tests can only detect infections caused by
L.
pneumophila
serogroup 1, a PCR test embracing all the serogroups could
increase the ability to diagnose these infections.
The detection of the products amplified by a method based on a double
hybridization enhances the specificity of the test and reinforces its sensitivity.
Most of the PCR tests used detection systems that are either less sensitive or
too demanding.
