Volume 12, Number 4—April 2006
Research
Reducing Legionella Colonization of Water Systems with Monochloramine
Brendan Flannery*
, Lisa B. Gelling†, Duc J. Vugia‡, June M. Weintraub§, James J. Salerno¶, Michael J. Conroy¶, Valerie A. Stevens*, Charles E. Rose*, Matthew R. Moore*, Barry S. Fields*, and Richard E. Besser*
, Lisa B. Gelling†, Duc J. Vugia‡, June M. Weintraub§, James J. Salerno¶, Michael J. Conroy¶, Valerie A. Stevens*, Charles E. Rose*, Matthew R. Moore*, Barry S. Fields*, and Richard E. Besser*Table 4
Factors associated with Legionella colonization at point-of-use outlets in sampled buildings, San Francisco, California
| Factor | No. samples | % Legionella colonization | Adjusted prevalence ratio (95% CI)* | p value |
|---|---|---|---|---|
| Residual disinfectant | ||||
| Chlorine | 617 | 39 | Referent | |
| Chloramine | 627 | 1 | 0.04 (0.02–0.09) | <0.001 |
| Water heater colonized with Legionella spp. | ||||
| Yes | 182 | 74 | 1.74 (1.26–2.40) | <0.001 |
| No | 1,062 | 11 | Referent | |
| Temperature of water at point-of-use outlet, °C | ||||
| <30 | 23 | 13 | Referent | |
| 30–39 | 268 | 24 | 0.90 (0.39–2.08) | 0.8 |
| 40–49 | 786 | 22 | 0.85 (0.35–2.05) | 0.7 |
| >50 | 175 | 10 | 0.75 (0.29–1.90) | 0.5 |
| Building height (stories) | ||||
| 3–10 | 855 | 15 | Referent | |
| >10 | 397 | 31 | 1.85 (1.46–2.35) | <0.001 |
| Disruption in service in last 3 mo | ||||
| Yes | 142 | 23 | 1.34 (0.99–1.81) | 0.06 |
| No | 1,109 | 20 | Referent | |
*Prevalence ratios and 95% confidence intervals (CIs) were adjusted for repeated sampling and correlations between samples taken from the same building and for the effects of all other variables. Twenty-eight observations were missing.
