Molecular detection of highly virulent Legionella pneumophila: Validation of a novel lag-1 targeted qPCR
In brief
A lag-1 test detected higher-virulence Legionella strains with 95% sensitivity
In respiratory samples, the gene-targeted test detected Legionella pneumophila strains associated with higher virulence with 95.48% sensitivity and 98.58% specificity against antibody-based typing; results fully matched in 239 of 248 specimens. The culture-independent assay could help identify these strains faster, but its impact on diagnosis and public health decisions remains to be established.
- Journal
- International journal of medical microbiology : IJMM (Q1)
- Published
- 11 October 2026
- Study design
- Unclassified
- Evidence level
- Level 5, Expert Opinion (CEBM 5)
- Authors
- Sarah Uhle, Laurine Wehmeier, Susan Wünsche, Anastasia Flountzi, Sophie Jarraud, Markus Petzold
- PMID
- 42994217
- DOI
- 10.1016/j.ijmm.2026.151746
Why clinicians should know about it
- Picked for Microbiology (medical) (top studies of the week, 8 November 2026): Validates rapid lag-1 qPCR detection of virulent Legionella
Abstract
BACKGROUND: Legionella pneumophila is the causative agent of legionellosis and is primarily associated with L. pneumophila serogroup 1 (Lp1). Strains reactive with the monoclonal antibody (mAb) 3/1 are associated with higher virulence and are predominantly responsible for clinical cases. The reactivity with mAb 3/1 correlates with the presence of the lag-1 gene, encoding an O-acetyltransferase that modifies lipopolysaccharides on the bacterial membrane. Despite its clinical importance, rapid and reliable tools for detecting lag-1+ strains are limited. OBJECTIVES: We aimed to develop and validate a quantitative real-time PCR (qPCR) assay targeting the lag-1 gene for detecting mAb 3/1+L. pneumophila strains. METHODS: Primers and probes were designed to amplify all known lag-1 allelic variants. The assay was validated with regard to specificity, sensitivity, limit of detection (LoD), and quantification (LoQ). Clinical evaluation was performed on 249 respiratory samples, comparing lag-1 qPCR results with mAb-based typing results, especially reactivity with mAb 3/1, of isolates and whole genome sequencing. RESULTS: The qPCR assay demonstrated complete concordance and amplified all lag-1 variants without cross-reactivity during validation. The LoD was 10 GU/reaction, and the LoQ was 50 GU/reaction. Using clinical samples, the assay showed a sensitivity of 95.48% and a specificity of 98.58% compared with mAb-based typing. From 248 specimens, 239 showed a complete concordance between the lag-1 qPCR and mAb-typing CONCLUSION: The lag-1 qPCR assay offers a culture-independent, rapid, and sensitive method for detecting virulent mAb 3/1+L. pneumophila strains. This tool has the potential to enhance diagnostic workflows and guide public health interventions by integrating virulence markers into risk assessment protocols.
Abstract as published, via PubMed.
For healthcare professionals. The summary is generated by AI from the published abstract, and the evidence level is assigned automatically from the study design on the Oxford CEBM hierarchy. Neither is medical advice. Read the full paper before changing practice.