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Microorganisms
Volume 13
Issue 12
10.3390/microorganisms13122832
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This is an early access version, the complete PDF, HTML, and XML versions will be available soon.
Article

Unravelling the Genomic and Virulence Diversity of Legionella pneumophila Strains Isolated from Anthropogenic Water Systems

by
Sofia Barigelli
1,
Piotr Koper
2,3,
Maya Petricciuolo
1,
Andrea Firrincieli
4,
Marta Palusińska-Szysz
2 and
Ermanno Federici
1,*
1
Laboratory of Applied and Environmental Microbiology, Department of Chemistry, Biology and Biotechnology, University of Perugia, 06122 Perugia, Italy
2
Department of Genetics and Microbiology, Institute of Biological Sciences, Maria Curie-Skłodowska University, 20-033 Lublin, Poland
3
Bioinformatics and Biostatistics Laboratory, Institute of Biological Sciences, Maria Curie-Skłodowska University, 20-033 Lublin, Poland
4
Department for Innovation in Biological, Agro-Food and Forest Systems, University of Tuscia, 01100 Viterbo, Italy
*
Author to whom correspondence should be addressed.
Microorganisms 2025, 13(12), 2832; https://doi.org/10.3390/microorganisms13122832
Submission received: 3 November 2025 / Revised: 29 November 2025 / Accepted: 3 December 2025 / Published: 12 December 2025
(This article belongs to the Special Issue Legionella pneumophila: A Microorganism with Thousand Faces, 2nd Edition)
Review Reports Versions Notes

Abstract

Legionella pneumophila, a waterborne pathogen naturally present in freshwater and capable of colonizing artificial water systems, is responsible for Legionnaires’ disease (LD), a severe form of pneumonia transmitted through inhalation of contaminated aerosols. Virulence of Legionella strains is affected by the plasticity of their genome, shaped by horizontal gene transfer and recombination events. Thus, contaminated water systems can host diverse Legionella populations with a distinct virulence potential. Here, we compare the genomic diversity of Legionella pneumophila strains isolated in water systems of academic buildings, together with their cytotoxicity and intracellular replication in THP-1-like macrophages. A six-year environmental surveillance revealed Legionella pneumophila contamination in 20 out of the 50 monitored sites, identifying five serogroups (sg) and 13 Sequence Types (STs). Phylogenetic investigations based on core genome multilocus sequence typing (cgMLST) and comparative genomics of representative isolates of each ST showed a broad diversity and a heterogeneous virulence repertoire, especially within the Dot/Icm and Lvh secretion systems. Following macrophage infection, a strain-dependent cytotoxicity and intracellular replication was observed, underlying significant pathogenic diversity within the same species and stage-dependent infection dynamics. Together, these results showed strain-specific genetic and phenotypic virulence traits to be considered during risk assessment in environmental surveillance.
Keywords: Legionella pneumophila; environmental strains; SBT; cgMLST; pangenome; virulence factors; cytotoxicity; intracellular replication Legionella pneumophila; environmental strains; SBT; cgMLST; pangenome; virulence factors; cytotoxicity; intracellular replication

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MDPI and ACS Style

Barigelli, S.; Koper, P.; Petricciuolo, M.; Firrincieli, A.; Palusińska-Szysz, M.; Federici, E. Unravelling the Genomic and Virulence Diversity of Legionella pneumophila Strains Isolated from Anthropogenic Water Systems. Microorganisms 2025, 13, 2832. https://doi.org/10.3390/microorganisms13122832

AMA Style

Barigelli S, Koper P, Petricciuolo M, Firrincieli A, Palusińska-Szysz M, Federici E. Unravelling the Genomic and Virulence Diversity of Legionella pneumophila Strains Isolated from Anthropogenic Water Systems. Microorganisms. 2025; 13(12):2832. https://doi.org/10.3390/microorganisms13122832

Chicago/Turabian Style

Barigelli, Sofia, Piotr Koper, Maya Petricciuolo, Andrea Firrincieli, Marta Palusińska-Szysz, and Ermanno Federici. 2025. "Unravelling the Genomic and Virulence Diversity of Legionella pneumophila Strains Isolated from Anthropogenic Water Systems" Microorganisms 13, no. 12: 2832. https://doi.org/10.3390/microorganisms13122832

APA Style

Barigelli, S., Koper, P., Petricciuolo, M., Firrincieli, A., Palusińska-Szysz, M., & Federici, E. (2025). Unravelling the Genomic and Virulence Diversity of Legionella pneumophila Strains Isolated from Anthropogenic Water Systems. Microorganisms, 13(12), 2832. https://doi.org/10.3390/microorganisms13122832

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