Severe pneumonia caused by Legionella pneumophila detected by a multiplex polymerase chain reaction assay and confirmed by serology

Abstract

Legionella pneumophila is a rarely diagnosed microorganism in Serbia. It causes legionellosis, usually a mild respiratory infection. However, in some cases it can be severe and even life threatening. In June 2020, during the COVID-19 pandemic, a patient with symptoms of the aforesaid infection, namely severe pneumonia and acute respiratory distress syndrome, was admitted to the hospital. The multiplex polymerase chain reaction (PCR) test (The BioFire FilmArray Pneumonia Panel plus) detected the presence of L. pneumophila in the patient’s bronchial secretions. The specific culture for the detection of that organism, however, remained sterile. The patient’s paired sera had been sent for serology and the results in both of them came back positive for Legionella spp. 1–6, while the assays specific for each one of the 10 serogroups detected more than a fourfold increase of antibody titers in an uncommon serogroup 2 only. The patient was treated with moxifloxacin; he recovered well and was discharged after 26 days of hospitalization. Having being diagnosed with the L. pneumophila infection correctly through the multiplex PCR test, the patient was given the right therapy with moxifloxacin. The serologic assays corroborated this result and revealed the uncommon group 2, thus confirming the necessity of carrying out all the tests available to attain the exact diagnosis of legionellosis.