RESUMO
Although measures to minimize Legionella colonization in sanitary hot water installations are well established, there is little evidence of their long-term effectiveness in hospital buildings. During an 8-year period, hot water in a large hospital building was sampled monthly in areas with suitable dimensioning and recirculation and in areas with dead legs and low-use taps. In the former areas, the percentage of Legionella-negative samples was 83.2% when the temperature was ≥55%, 64.9% when between 50.1⯰C and 54.0⯰C, and 51.6% when ≤50⯰C (p for trend <0.001). In the highest temperature group, no samples with ≥103â¯cfu/L were observed. In poorly designed areas, only 44.7% of samples were negative, and 28.9% presented ≥103â¯cfu/L although reaching 55⯰C. In these areas, multivariate analysis showed that if hot water supplies were not used daily, the risk of Legionella colonization was greater than two-fold (odds ratio: 2.84; 95% confidence interval: 1.26-6.41), and the risk of finding Legionella concentrations ≥103â¯cfu/L was more than three-fold (odds ratio: 3.18; 95% confidence interval: 1.36-7.46), regardless the temperature. These findings indicate that the effectiveness of maintaining sanitary hot water at a minimum temperature of 55⯰C is significantly better than that at 50⯰C for the environmental control of Legionella but only in installations with suitable dimensioning and recirculation. In installations that do not meet these conditions, high temperatures alone result in insufficient control.