Detection of Legionella DNA in guinea pig peripheral leukocytes, urine and plasma by the polymerase chain reaction

Legionella DNA has been detected in respiratory tract, serum and urine samples from patients with pneumonia by the polymerase chain reaction. A guinea pig model was used to assess whether Legionella DNA could also be detected in peripheral leukocytes during active infection. Ten guinea pigs were infected intraperitoneally with Legionella pneumophila serogroup 1, and leukocyte, plasma and urine samples were collected immediately before inoculation and on days 1, 3, 7 and 14 thereafter. All samples were tested for Legionella DNA by the polymerase chain reaction. Overall, Legionella DNA was detected in 55% of leukocyte samples, 28% of urine samples and 21% of plasma samples collected after inoculation. The sensitivity of the polymerase chain reaction on leukocytes was highest for samples collected within 3 days of inoculation. Further studies testing leukocyte samples from human Legionella infection are required to confirm these observations.