Modelling characteristics to predict Legionella contamination risk - Surveillance of drinking water plumbing systems and identification of risk areas.
For the surveillance of drinking water plumbing systems (DWPS) and the identification of risk factors, there is a need for an early estimation of the risk of Legionella contamination within a building, using efficient and assessable parameters to estimate hazards and to prioritize risks. The precision, accuracy and effectiveness of ways of estimating the risk of higher Legionella numbers (temperature, stagnation, pipe materials, etc.) have only rarely been empirically assessed in practice, although there is a broad consensus about the impact of these risk factors. We collected n = 807 drinking water samples from 9 buildings which had had Legionella spp. occurrences of >100 CFU/100mL within the last 12 months, and tested for Legionella spp., L. pneumophila, HPC 20°C and 36°C (culture-based). Each building was sampled for 6 months under standard operating conditions in the DWPS. We discovered high variability (up to 4 log(10) steps) in the presence of Legionella spp. (CFU/100 mL) within all buildings over a half year period as well as over the course of a day. Occurrences were significantly correlated with temperature, pipe length measures, and stagnation. Logistic regression modelling revealed three parameters (temperature after flushing until no significant changes in temperatures can be obtained, stagnation (low withdrawal, qualitatively assessed), pipe length proportion) to be the best predictors of Legionella contamination (>100 CFU/100 mL) at single outlets (precision = 66.7%; accuracy = 72.1%; F(0.5) score = 0.59).
Institute for Hygiene and Public Health, University of Bonn, Sigmund-Freud-Str. 25, 53105 Bonn, Germany. Electronic address: Sebastian.Voelker@ukb.uni-bonn.de.
Sebastian
S
Völker
Institute for Hygiene and Public Health, University of Bonn, Sigmund-Freud-Str. 25, 53105 Bonn, Germany. Electronic address: Christiane.Schreiber@ukb.uni-bonn.de.
Christiane
C
Schreiber
Institute for Hygiene and Public Health, University of Bonn, Sigmund-Freud-Str. 25, 53105 Bonn, Germany. Electronic address: Thomas.Kistemann@ukb.uni-bonn.de.
Thomas
T
Kistemann
D015169:Colony Count, Microbial; D060766:Drinking Water / Q000382:microbiology*; D006801:Humans; D007875:Legionella; D016952:Legionella pneumophila / Q000254:growth & development*; D016015:Logistic Models; D008954:Models, Biological; D018570:Risk Assessment; D012498:Sanitary Engineering / Q000592:standards*; D013696:Temperature; D014871:Water Microbiology; D014873:Water Pollutants; D014876:Water Pollution / Q000032:analysis; D014881:Water Supply / Q000592:standards*
D060766:Drinking Water; D014873:Water Pollutants
Contamination risk prediction; Drinking water plumbing systems; Germany; Legionella; Risk assessment