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

Abstract

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.

Comparison of the method of quantitative determination of <i>Legionella pneumophila</i> acc. to PN-EN ISO 11731:2017 with the Legiolert™/Quanti-Tray® (IDEXX)

“…Published data also confirm that hot water systems are an important reservoir from the point of view of risks to human health in which Legionella can multiply, especially if the water temperature is too low (<50 o C), there is a lack of flow or stagnant water and biofilm is present [10,14,15,16,17,19,20]. The persistence of such conditions in domestic distribution water systems, especially in facilities identified as a priority (e.g., hospitals or hotels), can pose a major threat to the health of the people using such systems [16,21,22]. Other factors conducive to the occurrence and proliferation of Legionella are oversized water systems, corrosion of construction materials, changes in water pressure, inadequate concentration of disinfectants or lack thereof, the presence of blind ends or dead legs, and seasonality of facility operation [10,11,14,17,19,23].…”

“…In this case, infections are often associated by using showers when, through inhalation of contaminated aerosolized water, pathogens can enter the alveoli directly and result in infection [10,11,14,15,17]. Published data also confirm that hot water systems are an important reservoir from the point of view of risks to human health in which Legionella can multiply, especially if the water temperature is too low (<50 o C), there is a lack of flow or stagnant water and biofilm is present [10,14,15,16,17,19,20]. The persistence of such conditions in domestic distribution water systems, especially in facilities identified as a priority (e.g., hospitals or hotels), can pose a major threat to the health of the people using such systems [16,21,22].…”

“…It is estimated that about 2-5% of legionellosis cases are caused by infection with species other than L. pneumophila, including: L. anisa, L. bozemanii, L. longbeachae, L. micdadei [3,4,5,6,7]. Many experts, including those at the WHO, have pointed out that in the European Union countries, of all waterborne pathogens, Legionella cause one of the greatest health burdens, and the number of registered cases of the disease is steadily increasing [3,4,14,15,16].…”

The impact of DNA extraction on the quantification ofLegionella, with implications for ecological studies

“…In the context of the microbial ecology of Legionella, the relevance of this is mainly linked to the observational studies aiming at understanding how this opportunistic pathogen lives in aquatic systems through their relationship with the surrounding organisms (Paranjape et al ., 2020, Paranjape et al ., 2020, Scaturro et al ., 2022). In a previous paper from our group, for example, we observed that Legionella spp.…”

Legionellarelative abundance in shower hose biofilms is associated with specific microbiome members

“…Paranjape and colleagues conducted two studies on cooling tower water and found that the genus Pseudomonas exhibited a strong negative correlation with Legionella, which, in turn, positively correlated with the genus Brevundimonas; the latter positive interaction has been further demonstrated in laboratory experiments with pure culture isolates. Scaturro and co-workers (Scaturro et al, 2022) investigated building plumbing water samples from several European cities and found positive correlations with bacteria of the genus Nitrospira, while observing negative associations with the genera Pseudomonas and Sphingopyxis.…”