Detection of <i>Legionella</i> species other than <i>Legionella pneumophila</i> in formalin‐fixed paraffin‐embedded tissue: An autopsy case study

Diagnosing the cause of death can be challenging, particularly for patients with no prior history of visits to the treating hospital. We encountered a case involving a 76-year-old male who was discovered in a state of cardiopulmonary arrest at his home and subsequently declared deceased in our hospital due to severe pneumonia. He had exhibited symptoms of fever over 37°C and severe coughing for several days. Despite consulting a primary care physician one day prior, his symptoms worsened. Autopsy findings revealed an increase in lung weight and diffuse changes in parenchyma. Histological analysis showed numerous inflammatory cells and exudate within the alveoli. Gram and Periodic acid-Schiff staining were negative, but slight staining was observed in the cytoplasm of macrophages by Warthin-starry and Gimenez stains. Tests using a pan bacterial/viral detection kit and qualitative polymerase chain reaction (PCR) for Legionella pneumophila were negative. However, using deoxyribonucleic acid extracted from formalin-fixed paraffin-embedded lung tissue, PCR amplification of the ssrA gene of congeneric Legionella species yielded positive results. The results suggest that the cause of death was likely due to bacterial pneumonia caused by Legionella species.