Detection of Legionella-Specific DNA in Serum

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Abstract
This chapter investigates the presence of Legionella-specific DNA in patient serum using a 5S RNA PCR. The DNA extraction was monitored by a control PCR , which amplified part of the β-globin gene, and the specificity of the PCR was verified by a combination of Southern blotting with a 50-oligomer Legionella-specific probe and TaqI restriction digestion of the PCR products. The Biotest urinary antigen enzyme-linked immunosorbent assay was performed as per the manufacturer's instruction. The serology and culture tests were performed. In patients with multiple samples there were variations in PCR reactivity depending on the time of sample. In patient 10, the 5S RNA PCR was positive in the first two serum samples (the acute- and early convalescent-phase samples) but negative in the later two convalescent-phase serum samples. The Southern blotting has the advantage that it can be performed on all PCR reactions, but the Taql digest requires a PCR product to confirm the specificity of the PCR reaction. The 5S RNA PCR was sensitive and specific and should increase laboratory diagnosis of Legionella infection when there is a nonvalidated serological response.