Genome analysis of Legionella pneumophila ST23 from various countries reveals highly similar strains

Abstract

Legionella pneumophila serogroup 1 (Lp1) sequence type (ST) 23 is one of the most commonly detected STs in Italy where it currently causes all investigated outbreaks. ST23 has caused both epidemic and sporadic cases between 1995 and 2018 and was analysed at genomic level and compared with ST23 isolated in other countries to determine possible similarities and differences. A core genome multi-locus sequence typing (cgMLST), based on a previously described set of 1,521 core genes, and single-nucleotide polymorphisms (SNPs) approaches were applied to an ST23 collection including genomes from Italy, France, Denmark and Scotland. DNAs were automatically extracted, libraries prepared using NextEra library kit and MiSeq sequencing performed. Overall, 63 among clinical and environmental Italian Lp1 isolates and a further seven and 11 ST23 from Denmark and Scotland, respectively, were sequenced, and pangenome analysed. Both cgMLST and SNPs analyses showed very few loci and SNP variations in ST23 genomes. All the ST23 causing outbreaks and sporadic cases in Italy and elsewhere, were phylogenetically related independent of year, town or country of isolation. Distances among the ST23s were further shortened when SNPs due to horizontal gene transfers were removed. The Lp1 ST23 isolated in Italy have kept their monophyletic origin, but they are phylogenetically close also to ST23 from other countries. The ST23 are quite widespread in Italy, and a thorough epidemiological investigation is compelled to determine sources of infection when this ST is identified in both LD sporadic cases and outbreaks.

Genomic characterization and assessment of pathogenic potential of Legionella spp. isolates from environmental monitoring

“…Pangenome analyses focused on L. pneumophila have been previously performed on clinical and environmental isolates ( Qin et al, 2016 ; Mercante et al, 2018 ; Ricci et al, 2022 ) The similar number of genes included in the core genome was obtained in this study, even though this study include by far the most L. pneumophila genomes which indicates the core genome has stabilized. The functional annotation shows that unique and accessory genes were required for replication, recombination, and repair, which is also in accordance with mentioned pangenome studies which suspect these genes were acquired by HGT.…”

CLEC12A Binds to Legionella pneumophila but Has No Impact on the Host’s Antibacterial Response

“…Indeed, several CLR-Fc fusion proteins (CLEC12A, Dectin-1, DC-SIGN and L-SIGN) exhibited moderate to substantial binding to L. pneumophila , with CLEC12A displaying the highest MFI signal compared with the hFc control and the other CLRs included in the library ( Figure 1 A). Since L. pneumophila serogroup 1 causes most of the worldwide outbreaks [ 32 ], we decided to test the wild-type strains JR32 and Corby, both categorized as serotype 1, for binding to CLEC12A [ 12 , 33 ]. To gain further insights into the role of major L. pneumophila pathogenicity factors in CLEC12A binding, a LPS mutant [ 33 ] and a flagellin mutant ( ΔflaA ) [ 34 ] were included in the binding assay.…”

Legionella pneumophila: The Journey from the Environment to the Blood

“…Legionella pneumophila is a genetically heterogeneous species, composed of a total of 32 Legionella species and 51 serogroups [ 19 , 20 ]. The Legionella pneumophila serogroup 1 (Lp1) is one of the most commonly detected strains that causes outbreaks worldwide [ 21 ]. It was also demonstrated that L. pneumophila consists of three subspecies: pneumophila, fraseri, and pascullei [ 22 , 23 ].…”