ViableLegionella pneumophilabacteria in natural soil and rainwater puddles

Abstract

Aims For the majority of sporadic Legionnaires’ disease cases the source of infection remains unknown. Infection may possible result from exposure to Legionella bacteria in sources that are not yet considered in outbreak investigations. Therefore, potential sources of pathogenic Legionella bacteria—natural soil and rainwater puddles on roads—were studied in 2012. Methods and Results Legionella bacteria were detected in 30% (6/20) of soils and 3·9% (3/77) of rainwater puddles by amoebal coculture. Legionella pneumophila was isolated from two out of six Legionella positive soil samples and two out of three Legionella positive rainwater samples. Several other species were found including the pathogenic Leg. gormanii and Leg. longbeachae. Sequence types (ST) could be assigned to two Leg. pneumophila strains isolated from soil, ST710 and ST477, and one strain isolated from rainwater, ST1064. These sequence types were previously associated with Legionnaires’ disease patients. Conclusions Rainwater and soil may be alternative sources for Legionella. Significance and Impact of the Study The detection of clinically relevant strains indicates that rainwater and soil are potential sources of Legionella bacteria and future research should assess the public health implication of the presence of Leg. pneumophila in rainwater puddles and natural soil.

Active and adaptive Legionella CRISPR‐Cas reveals a recurrent challenge to the pathogen

“…As L. pneumophila cycles through over at least 15 species of diverse protozoa in the environment (Rowbotham, ; Fields, ; Solomon et al , ; Molmeret et al , ), acquisition of LME‐1 would likely confer a costly host range switch under environmental conditions of sufficient host diversity. Note that this could occur within freshwater, the typical habitat of L. pneumophila (Fliermans et al , ), as Dictyostelium species have been observed in lakes and sediment (O'Dell, ; Richards et al , ; Somboonna et al , ; Shanan et al , ); at the same time, L. pneumophila has also been isolated from soil (Wallis and Robinson, ; Schalk et al , ; van Heijnsbergen et al , ), a long‐established habitat of D. discoideum (Singh, ). While D. discoideum is generally thought of within the context of a laboratory model for Legionella infection, these data suggest that further scrutiny should be placed on the natural association of L. pneumophila and D. discoideum in the environment.…”

Ten questions concerning the aerosolization and transmission of Legionella in the built environment

“…Although some of the bacteria in the soil may come from industrial waste or cooling towers, Rowbotham 111 suggested that amoebae in soil might enhance the growth of Legionella . Other potential sources include rainwater puddles, which have been found to harbor viable L. pneumophila , 112 and rooftop rainwater cisterns. 113-116 Legionella appears to be part of the natural aquatic microbiome, as it has been found in oceans, lakes, and rivers.…”

A cluster of Legionnaires' disease in Belgium linked to a cooling tower, August–September 2016: practical approach and challenges

“…Between 2000 and 2010, only 2.3% of the isolates (2/86) in the Belgian database were ST48 [17] and this was the first isolation of ST48 since 2008. The source of these isolates has never been determined, suggesting that these strains may be present in particular environmental niches unexplored so far [31][32][33][34][35]. The importance of these niches may be underestimated, as they may not yet be considered in source investigations and fall outside the legislative framework for (high) risk installations.…”