Scaturro, M. | Search bioRxiv

bioRxiv2023

Genome analysis of Legionella pneumophila ST901 an Italian endemic strain.

Legionella pneumophila typing, based on SBT analysis, has been allowing to identify sequence types (ST) responsible for many Legionnaires disease cases. ST901 has so far been identified only in a town of the northern Italy, where it caused numerous travel-associated Legionnaires disease cases over a 32-year period. In this study, ST901 were analyzed by whole genome sequencing in looking for both differences and similarities inside this ST and with other unrelated Legionella strains. To this aim core genome multi locus sequence type, single nucleotide polymorphisms and pangenome analyses were performed. ST901 resulted highly similar each other, characterized by I-C CRISPR-cas system, located on the chromosome and by a putative plasmid, highly similar to that found in Lp strain Lens, which contains I-F CRISPR-cas system. Accessory genomic islands, either already described or specifically found in ST901, were also shown. In conclusion ST901 has been quite preserved over the time. The co-occurrence of two phage resistance systems and genomic islands of virulence could have made the ST901 enough virulent to cause such a high number of cases. Summary blurbST901 appears as endemic of the Northern Italy, with virulence traits similar to those in Alcoy and Corby, and with two CRISPR-cas systems which probably preserved them in their environmental niche.

genomics↗

bioRxiv2022

Bacterial communities of premise plumbing systems in four European cities, and their association with culturable Legionella

Legionella species are Gram negative, facultative, intracellular bacteria found in natural and engineered water systems. Understanding the bacterial interactions underlying the success of Legionella in aquatic environments could be beneficial for control. We aimed to profile, by 16S rRNA amplicon sequencing, the bacterial communities in premise plumbing systems of buildings in four European cities (Copenhagen, Warsaw, Rome, Athens), and identify positive and negative associations of specific community members to culturable Legionella. The coarse taxonomic composition was similar across the four cities, but Copenhagen and Warsaw had richer, more diverse communities than Athens and Rome, with a greater number of city-specific amplicon sequence variants (ASVs). The cities had statistically significant differences in bacterial communities at the ASV level, with relatively few shared ASVs. Out of 5,128 ASVs, 73 were classified as Legionella, and one or more of these were detected in most samples from each city (88.1% overall). Interestingly, the relative abundance of Legionella ASVs did not correlate with Legionella culture status. Overall, 44.2% of samples were Legionella culture positive: 71.4% in Warsaw, 62.2% in Athens, 22.2% in Rome, and 15.2% in Copenhagen. 54 specific ASVs and 42 genera had significant positive or negative associations with culturable Legionella. Negative associations included Staphylococcus, Pseudomonas, and Acinetobacter. Positive associations included several Nitrospira ASVs and one classified as Nitrosomodaceae oc32, ASVs in the amoeba-associated genera Craurococcus-Caldovatus and Reyranella, and the predatory genus Bdellovibrio. Some of these associations are well supported by laboratory studies, but others are the opposite of what was expected. This highlights the difficulties in translating pure culture results to into complex real-life scenarios. However, these positive and negative associations held across the four cities, across multiple buildings and plumbing compartments. This is important because developing better control measures, including probiotic approaches, will require an understanding of ecological relationships that can be generalised across different engineered water systems. ImportanceThis study provides a snapshot of the diversity of microbial communities among premise plumbing systems in four European cities, providing new information on bacterial ASVs and genera that have positive or negative associations with culturable Legionella across a broad geographical and climatic range. This could inform studies aimed at confirming both in vitro and real-life scenarios around the role of other microbial community members in modulating Legionella proliferation. It could also help in the development of probiotic approaches to controlling this opportunistic pathogen.

microbiology↗