This study analyzed antimicrobial resistance genes in 522 Legionella pneumophila isolates using whole-genome sequencing (WGS) and validated resistance phenotypes through phenotypic testing. The results revealed inconsistencies between resistance genes and phenotypes, emphasizing that gene presence alone does not guarantee phenotypic resistance and highlighting the necessity of phenotypic verification.
Literature Overview
The article 'Comparison of Phenotypic and Whole-Genome Sequencing-Derived Antimicrobial Resistance Profiles of Legionella pneumophila Isolated in England and Wales from 2020 to 2023' published in the journal *Antibiotics* reviews the distribution of resistance genes in Legionella pneumophila across the UK and Wales and their phenotypic validation. The study systematically evaluated the functional significance of resistance genes in Legionella pneumophila by integrating whole-genome sequencing (WGS) with minimum inhibitory concentration (MIC) testing.
Background Knowledge
Legionella pneumophila is the primary causative agent of Legionnaires' disease, typically transmitted through inhalation of contaminated water mist. While clinical resistance remains rare, resistant strains have emerged in recent years, particularly drawing attention to macrolide and fluoroquinolone resistance. Resistance can arise through gene mutations or acquired resistance genes (ARGs), such as 23S rRNA mutations, lpeAB efflux pumps, and blaOXA-29 β-lactamase. However, standardized resistance detection guidelines are lacking, and phenotypic testing results vary due to charcoal supplementation in media. Consequently, combining genomic analysis with phenotypic testing has become a research focus to improve resistance prediction accuracy and guide clinical treatment.
Research Methods and Experiments
The study analyzed 522 Legionella pneumophila isolates collected between 2020 and 2023 in England and Wales, including 281 clinical and 241 environmental isolates. Serotyping was performed using qPCR and monoclonal antibody (mAb) methods, while sequence typing (ST) employed Sanger sequencing. Whole-genome sequencing (WGS) screened for resistance genes and key mutations, such as 23S rRNA, gyrA, and rplD. Isolates carrying specific resistance genes underwent minimum inhibitory concentration (MIC) testing to compare phenotypic resistance.
Key Conclusions and Perspectives
Research Significance and Prospects
This study validates the limitations of current resistance gene screening in Legionella pneumophila, showing gene presence alone cannot reliably predict phenotypic resistance. Future studies should integrate long-read sequencing to resolve genomic contexts of resistance genes and employ expression analysis to investigate regulatory mechanisms. As metagenomic testing expands in clinical settings, developing reliable resistance prediction tools is critical for guiding treatment decisions and infection control.
Conclusion
This study systematically examined the relationship between resistance genes and phenotypes in Legionella pneumophila from England and Wales (2020–2023). While lpeAB showed significant association with elevated macrolide MICs, the limited increase magnitude and overlapping distributions precluded definitive resistance criteria. blaOXA-29 and aph(9)-Ia failed to demonstrate phenotypic resistance, underscoring the need to combine mutation analysis and expression studies for accurate resistance prediction. The 23S rRNA mutation proved highly reliable as a resistance marker. The findings emphasize that sole reliance on resistance gene detection risks misguiding treatment decisions, advocating for integrated genomic and phenotypic testing to enable precision antimicrobial therapy.
