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[A pilot study on the value of duplex polymerase chain reaction method in early diagnosis of Legionella pneumonia].

OBJECTIVE
To investigate the value of duplex polymerase chain reaction (DPCR) in early diagnosis of Legionella pneumonia by detecting Legionella DNA in sputum and bronchoalveolar lavage fluid(BALF).


METHODS
During the process of DPCR, two different sets of oligonucleotide primers were simultaneously used to amplify 386bp 16SrRNA gene fragment and 206bp mip gene fragment. These two primers were designed according to the sequences of 16SrRNA gene and mip gene of Legionella. The sputum and BALF of patients from two groups, including a Legionella pneumonia group (n = 15) and an ordinary pneumonia group (n = 31) were collected at early course of the disease. All of the samples were detected with DPCR for Legionella DNA. Simulated samples were also detected to investigate the sensitivity of the method for testing clinical samples.


RESULTS
All the samples collected from the Legionella pneumonia patients, including 25 of sputum,and 8 of BALF showed positive DPCR. The results of DPCR, which could distinguish Legionella pneumophila from non-pneumophila Legionella spp. to some degree, were in good accordance with those of the specific serum antibodies. All of the samples from the ordinary pneumonia group including 40 of sputum and 16 of BALF demonstrated negative DPCR. Different samples of the same patient showed the same DPCR results. The lowest detection level of simulated sputum sample was the same as that of simulated BALF sample, being 1 x 10(3) cfu/ml.


CONCLUSIONS
This preliminary study showed that DPCR had satisfactory sensitivity, specificity and stability for detecting Legionella DNA in sputum and BALF. The method is of value in early diagnosis of Legionella pneumonia. Its wide use for clinical work requires further investigation.