87
beginning of the antibiotic therapy. The cited disadvantages, though, are
the cross-reactivity with non-Legionella bacteria and the necessity of
experienced professional to perform the test.
The Figure 02 below illustrates the microscopic aspect of
Legionella
pneumophilain
tests of direct fluorescence.
6.1.3 SerologicDiagnosis by Indirect Fluorescent Antibody Test (IFA)
The search of antibodies in serumsamples through techniques of indirect
immunofluorescence (IFA) is highly recommended to assist in the diagnosis
of Legionellosis, specially when it is not possible to obtain proper respiratory
samples for both the cultivation and the DFA. This method has sensitivity
ranging from 75 to 80%, andspecificity of 96%.
It is to be expected in 2 to 6 weeks for the detection of four-time increase
in the initial titer and it can present cross-reactivity with
Bacteroides fragilis
,
Proteus vulgaris
, species of
Rickettsia
and
Citrobactrer
.
The limitations for the method are: even in cases confirmed by culture,
the increase of four times in the antibody titer is documented only in 70 to
80% of the patients; the serum conversion may not occur until two months
Figure 02
–
Legionella pneumophilain
tests of direct
fluorescence.
