[A Case of Severe Legionella longbeachae Pneumonia and Usefulness of LAMP Assay].

Abstract

Urinary antigen test is frequently used as a routine laboratory test for early diagnosis of Legionella infection, which is especially suitable for ordinary Legionella pneumophila serogroup 1, but not for other types of Legionella. We report a case of severe pneumonia caused by Legionella longbeachae, where a method of loop-mediated isothermal amplification (LAMP) assay contributed an important role for the early detection. This case involved an 83-year-old man who developed fever, dyspnea, and productive cough. Since the medication of prescribed ceftriaxone had not been effective, he visited the emergency room of our hospital, where an X-ray revealed a severe pneumonia harboring a consolidation with air bronchogram in his right lower lung. His sputum and urine were subjected to the routine bacterial culture or the urinary antigen test for Legionella, which initially brought negative results. However, a positive result of LAMP assay enabled early diagnosis of Legionella pneumonia. Later, the bacterial cultures of sputum made some progress and 16S rRNA sequencing provided a proof of L. longbeachae. This LAMP assay may bring a benefit for the patients with Legionella pneumonia by enabling early detection of not only specific L. pneumophila serogroup 1, but also of the other Legionella species.