A test system supplied with different types of warm drinking water without disinfectant under controlled hydraulic conditions showed that treated aerobic groundwater (0.3 mg C per liter of organic carbon) induced a low biofilm concentration that supported no or very limited growth of L. pneumophila. Elevated biofilm concentrations and L. pneumophila colony counts were observed on surfaces exposed to two types of extensively-treated groundwater containing 1.8 and 7.9 mg C per liter and complying with the microbial water quality criteria during distribution. Control measures in the warm tap water installations therefore are essential for preventing growth of L. pneumophila.

Read more: http://aem.asm.org/content/early/2016/12/12/AEM.02737-16.abstract

Implication: Respirators, C-PAPs, humidifiers and other devices that use distilled water may be safe from Legionella.