Abstract
BackgroundRisk for infections from Legionella pneumophila for immunocompromised individuals increases greatly when this species is present within the biofilm of the water distribution systems of hospitals or other health facilities. Multiplication and persistence of Legionella may dependent also upon planktonic growth in alternative to sessile growth. Here we compared the persistence of L. pneumophila serogroup 1 in experimental planktonic co-cultures subsided with iron, Pseudomonas aeruginosa and other non Legionella bacteria (quantified as Heterotrophic Plate Count, HPC at 37°C), isolated from drinking water sources of a large hospital.ResultsConcentrations of L. pneumophila showed a decreasing pattern with incubation time in all co-cultures, the degree of reduction depending on the experimental treatment. In co-cultures with added P. aeruginosa, no L. pneumophila was detectable already after 4 days of incubation. In contrast in co-cultures without P. aeruginosa, HPC but not iron were significant factors in explaining the pattern of L. pneumophila, although the HPC effect was different according to the incubation time (HPC x time interaction, p < 0.01).ConclusionsOur results highlight the need of controlling for both HPC and metal constituents of the water systems of buildings used by individuals at particular risk to the effects of Legionella exposure.
Highlights
Risk for infections from Legionella pneumophila for immunocompromised individuals increases greatly when this species is present within the biofilm of the water distribution systems of hospitals or other health facilities
The aim of this study is to test the persistence of L. pneumophila in experimental planktonic cocultures subsided with iron, P. aeruginosa and other non Legionella bacteria isolated from the drinking water of a large hospital
Study design To test the effect of subsidy of iron, other non Legionella bacteria and P. aeruginosa copresence on L. pneumophila, we set up a full factorial design with iron (2 levels: 0 and 0.1 mg/l initial concentrations), HPC at 37°C (3 levels: 0, 10 and 100 CFU/ml initial concentrations) and P. aeruginosa (2 levels: 0 and 10 CFU/ml initial concentrations) as factors
Summary
Risk for infections from Legionella pneumophila for immunocompromised individuals increases greatly when this species is present within the biofilm of the water distribution systems of hospitals or other health facilities. When colonizing the water distribution systems of buildings of hospitals or other health facilities, the risk for infections for immunocompromised individuals increases greatly. In such artificial aquatic systems, the biofilm covering the interior of pipelines and, more in general, the various plumbing elements represent relatively nutrient-rich spots where Legionella (and other bacteria) can attach and multiply [1,2]. As iron availability in water distribution systems may be linked with the older age and metal constituents of pipes [13], corrosion products are important factors in the survival and growth of L. pneumophila in artificial habitats [13,16]
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