Legionelloses Caused by Non-Pneumophila Legionella Species and Their Diagnosis: A Narrative Review

Abstract

The genus Legionella is comprised of over 60 different species including the first described and most notorious one, L. pneumophila. However, although less well-known, other species of this genus also have a pathogenic potential. This review investigates 226 reports of legionellosis caused by Non Pneumophila Legionella species retrieved. Among those reports, at least one instance of human infection was found for 27 Non-Pneumophila Legionella species. Infection of the respiratory tract was the most frequent clinical presentation, with over 75% of the reports. Cardiac and skin/soft tissue infections ranked second and third (7% and 6% of the reports, respectively). The top three species were L. longbeachae (24.2% of the reports), L. micdadei (23.2%) and L. bozemanae (13.2%). L. micdadei was the prominent species involved in pneumonia and Pontiac fever outbreaks. L. longbeachae distinguished itself by its peculiar reservoir which was identified as soil/potting mix, as opposed to water for all of the other Non-Pneumophila species. Historically, infections caused by Non Pneumophila Legionella species were first identified in immunocompromised subjects. However, over the last decade, reports of infections in immunocompetent subjects have outnumbered those in immunocompromised ones. This observation coincides with the development and wider use of non-targeted molecular biology diagnostic methods such as broad range PCR and metagenomic next-generation sequencing. If these methods are progressively included in the routine workflow of microbiology labs, a better picture of the real contribution of Non-Pneumophila Legionella species to the overall legionellosis burden could be expected.

Keywords: Non-Pneumophila Legionella; Legionellosis; Diagnosis; Sequencing; MALDI-TOF

Citation

Catherine Mullié. Legionelloses Caused by Non-Pneumophila Legionella Species and Their Diagnosis: A Narrative Review. WebLog J Bacteriol. wjbct.2026.i0903. https://doi.org/10.5281/zenodo.22846983