Detection of Legionella species by polymerase chain reaction

The nested polymerase chain reaction (PCR) was clinically investigated to detect the mip gene of Legionella species. PCR detected 20 clinically important Legionella species, such as L. pneumophila, L. micdadei, and L. bozemanii. Eight species of Gram-positive and -negative bacteria other than Legionella species were negative for PCR. The sensitivity of PCR determined by the detection limit of DNA quantity was 1.0 pg for the first PCR, but the sensitivity increased approximately 100-fold to 10 fg following the second PCR. The nested PCR was applied to detect L. pneumophila in the sputum and pleural effusion fluid obtained from a patient with Legionnaires' disease. Both fluids were PCR positive, but culture was negative for L. pneumophila. Our results indicated that the nested PCR may be a useful tool for the rapid detection of L. pneumophila and the clinical diagnosis of Legionnaires' disease.