Advances in Legionella Control by a New Formulation of Hydrogen Peroxide and Silver Salts in a Hospital Hot Water Network

Abstract

Legionella surveillance is an important issue in public health, linked to the severity of disease and the difficulty associated with eradicating this bacterium from the water environment. Different treatments are suggested to reduce Legionella risk, however long-term studies of their efficiency are lacking. This study focused on the activity of a new formulation of hydrogen peroxide and silver salts, WTP828, in the hospital hot water network (HWN) to contain Legionella contamination during two years of treatment. The effectiveness of WTP828 was tested measuring physical-chemical and microbiological parameters such as Legionella, Pseudomonas aeruginosa (P. aeruginosa), and a heterotopic plate count (HPC) at 36 °C. Legionella isolates were identified by serotyping and genotyping. WTP 828 induced a reduction in Legionella–positive sites (60% to 36%) and contamination levels (2.12 to 1.7 log10 CFU/L), with isolates belonging to L. pneumophila SG1 (ST1 and ST104), L. anisa and L. rubrilucens widely distributed in HWN. No relevant contamination was found for other parameters tested. The long-term effect of WTP828 on Legionella containment suggest the easy and safe application of this disinfectant, that combined with knowledge of building characteristics, an adequate environmental monitoring and risk assessment plan, become the key elements in preventing Legionella contamination and exposure.

The Role of Sensor-Activated Faucets in Surgical Handwashing Environment as a Reservoir of Legionella

“…These results were also confirmed by our previous data [35] regarding the ability of Legionella to colonize and increase its concentration in cold-water distribution systems, inducing a change of cold water microflora; during renovation works, pipeline, TMV, and faucet damage; or when rapid breakdown of hot temperatures occurs. The presence of a high percentage of positive samples with high Legionella concentration contaminated by both species in both distribution systems confirms that SHWOs with mixed water develop an environment favorable to Legionella growth.…”

Management of Microbiological Contamination of the Water Network of a Newly Built Hospital Pavilion

“…The hydrogen peroxide and silver ions are active agents against bacteria, yeast, fungi, viruses, spores, proto-, and metazoans [ 30 ]; they are included in the Italian Guidelines for the Control and Prevention of Legionellosis [ 31 ]. It is compatible with different pipeline materials and does not react with the organic constituents in the water to form dangerous residues with respect to chlorine, sodium hypochlorite and monochloramine treatment [ 32 ]. European directives do not establish a concentration limit for hydrogen peroxide in drinking water, although the German and British version of the EN 902:2016 [ 33 ] provides a dosage up to 17 mg/L [ 17 ].…”

How Molecular Typing Can Support Legionella Environmental Surveillance in Hot Water Distribution Systems: A Hospital Experience

“…The hospital that was the subject of this study is organized in three separate buildings that use the same municipal water supply and three hot water return lines, which allowed a simultaneous and comparative study among the buildings. The introduction of a new disinfectant based on H 2 O 2 /Ag + in 2013 enabled the control of the level of contamination in relation to disinfectant dosage and creating a new water safety plan compliant with directives, as demonstrated by our previous data [ 35 ].…”

“…These data can be explained by building A having a larger surface area and lower water demand compared with the other buildings, as indicated by water consumption (938.98 m 3 /year for building A, 1745.44 m 3 /year for building B, and 450.62 m 3 /year for building C). The low water demand of building A is due to work areas such as offices and consulting rooms being closed during weekends and holidays, so daily water flushing is low, which can influence water stagnation and the biofilm community [ 35 , 36 ].…”