Necessity and Effect of Combating Legionella pneumophila in Municipal Shower Systems

Abstract

The objective was to obtain research-based, holistic knowledge about necessity and effect of practiced measures against L. pneumophila in municipal shower systems in Stavanger, Norway. The effects of hot water treatment and membrane-filtering were investigated and compared to no intervention at all. The studies were done under real-world conditions. Additionally, a surveillance pilot study of municipal showers in Stavanger was performed. The validity of high total plate count (TPC) as an indication of L. pneumophila was evaluated. A simplified method, named “dripping method”, for detection and quantification of L. pneumophila was developed. The sensitivity of the dripping method is 5 colony-forming units of L. pneumophila/ml. The transference of L. pneumophila from shower water to aerosols was studied. Interviews and observational studies among the stakeholders were done in order to identify patterns of communication and behavior in a Legionella risk perspective. No substantial effects of the measures against L. pneumophila were demonstrated, except for a distally placed membrane filter. No significant positive correlation between TPC and L. pneumophila concentrations were found. L. pneumophila serogroup 2–14 was demonstrated in 21% of the 29 buildings tested in the surveillance pilot. Relatively few cells of L. pneumophila were transferred from shower water to aerosols. Anxiety appeared as the major driving force in the risk governance of Legionella. In conclusion, the risk of acquiring Legionnaires' disease from municipal shower systems is evaluated as low and uncertain. By eliminating ineffective approaches, targeted Legionella risk governance can be practiced. Risk management by surveillance is evaluated as appropriate.

Response to Comments on Montagna et al. “Evaluation of Legionella Air Contamination in Healthcare Facilities by Different Sampling Methods: An Italian Multicenter Study” Int. J. Environ. Res. Public Health 2017, 14, 670

“…We apologize for not having mentioned this paper, but our Legionella data range in water samples agrees with results reported by Wiik et al [4]; that is, viable air-borne Legionella was infrequently detected at low concentrations in water samples.…”

“…The article of Wiik et al [4] reports that a high concentration of Legionella (>300,000 cfu/L) in water is required to detect Legionella in the air. We apologize for not having mentioned this paper, but our Legionella data range in water samples agrees with results reported by Wiik et al [4]; that is, viable air-borne Legionella was infrequently detected at low concentrations in water samples.…”

Legionella sp. in water systems in public teaching and education facilities in Małopolskie voivodeship in 2016

“…In 2018, a study was published in kindergartens, schools, sports buildings, office buildings and nursing homes in Norway regarding the assessment of the use of various methods, among others thermal disinfection and membrane filtration in the fight against Legionella pneumophila in urban shower systems. Active surveillance did not show a significant effect of the methods assessed and no significant positive correlation was found between the total heterotrophic number of platelets (heterotrophic bacteria index) and Legionella pneumophila concentration, and the risk of Legionella infection is assessed as low and uncertain (24). As part of the European Center for Disease Prevention and Control (ECDC), there is the European Legionnaires' Disease Surveillance Network (ELDSNet), whose role is to detect, control and prevention of individual cases, group infections and outbreaks of legionnaires' disease in EU / EEA countries, as well as assistance in other countries to this extent.…”

“…dezynfekcji termicznej i filtracji membranowej w zwalczaniu Legionella pneumophila w miejskich systemach prysznicowych. Aktywny nadzór nie wykazał istotnego wpływu ocenianych metod oraz nie stwierdzono istotnej dodatniej korelacji między stężeniem całkowitej heterotroficznej liczby płytek (wskaźnik obecności bakterii heterotroficznych) a stężeniem Legionella pneumophila, a ryzyko zakażenia pałeczkami Legionella ocenia się jako niskie i niepewne (24). W ramach Europejskiego Centrum ds.…”

Detection of Legionella Species and the Influence of Precipitation on the Amount of Legionella DNA Present in Aerosols from Outdoor Sites Near Asphalt Roads in Toyama Prefecture, Japan, with Microbiome Analysis

“…Legionella present in puddles on roads could be aerosolized by splashing or by wind. Recently, several studies have attempted to detect Legionella species in aerosols released from hot tap water in bathrooms, shower water, and compost [12][13][14]. These studies revealed that Legionella species were present in the aerosols derived from these environments.…”