Two cases of community acquired Legionella pneumophila non‐serogroup 1 in patients undergoing extra corporeal membrane oxygenation for severe respiratory failure

Abstract

Introduction: The Legionellaceae are fastidious Gram‐negative bacteria that reside in aquatic environments. They are a cause of severe community acquired pneumonia. Legionella pneumophila serogroup 1 is responsible for 70–90 % of human infection, with cases caused by some of the other 15 serogroups accounting for the rest. Most hospitals use the Legionella urinary antigen test for detection of legionellosis; however, this will only reliably detect L. pneumophila serogroup 1. Case presentation: We report two cases of severe community acquired pneumonia in patients requiring extracorporeal membrane oxygenation, referred to our adult Severe Respiratory Failure Unit. Legionella urinary antigen was negative in both cases. As clinical presentation strongly suggested Legionnaires’ disease (LD), respiratory samples were sent to the reference laboratory for PCR, which confirmed L. pneumophila non‐serogroup 1 in both cases. Case 1 was subsequently confirmed by culture and confirmed as L. pneumophila serogroup 5. Case 2 was culture‐negative. Conclusion: Legionella is an important pathogen. Recognition of the potential for non‐serogroup 1 strains to cause severe LD should prompt requests for further investigations including Legionella PCR in patients who present with suggestive symptoms when the urine antigen is negative. Reliance on the urine antigen test may result in a potentially serious under‐recognition of L. pneumophila non‐serogroup 1 and lead to mis‐diagnoses and inappropriate antimicrobial treatment.