**5. Conclusions**

It is often di fficult to guarantee the absence of *Legionella* from water distribution systems, even if a disinfection system is in place. Our data revealed that di fferences in three buildings belonging to the same structure were linked to building size, water consumption rates, the number of outlets, and their intended use. WTP 828 performed well in terms of reducing *Legionella* contamination, but only a change in the study approach (adequate risk assessment plan, increase in monitoring samples sites, and alteration of the WTP 828 dosage in relation to the *Legionella* levels) facilitated the discovery of di fferences in *Legionella* colonization and an understanding of disinfectant activity dynamics.

Further investigations are needed to elucidate how the dose of disinfectant a ffects the presence of specific strains in each building and to generate a risk map highlighting the phylogenetic correlations between strains. The assessment of changes in colonization dynamics will be useful for controlling the concentration and type of disinfectant that can be used in a water system (i.e., shock or continuous treatment, bacterial resistance development) in relation to accommodation works and technical operations in the water network that could support *Legionella* proliferation.

The low cost of WTP 828, the dosage by a pump, the easy maintenance procedures and simple and safe check of disinfectant residue at distal outlets, sugges<sup>t</sup> that the approach used in this study could be a valid alternative to traditional disinfection methods.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2076-0817/8/4/209/s1. Figure S1. Site map of MCH, Cotignola (RA), Italy. A representative view of MCH and a map of its three buildings: MCH picture (A) and MCH planimetry (B); Table S1. MCH structure and water outlet characteristics.

**Author Contributions:** S.C. and L.G. conceived, designed the experiments, wrote the paper, and performed the experiments; A.G. and G.F.S. performed the sequence analysis; A.D. performed the data analysis; D.M., A.C., F.S., and A.M. provided disinfectants and performed the water sample collection; T.P. and P.S. provided technical support to study the MCH hot water network.

**Funding:** This work was supported by a research gran<sup>t</sup> (RFO 2017) from University of Bologna, Italy.

**Acknowledgments:** The authors would like to thank the MCH sta ff for helping with the study, the technical sta ff at Water Team S.r.l. for assistance and provision of the WTP 828 disinfectant, Eta Beta S.r.l. for technical assistance, and Graziella Ciani for help with the microbiological analyses.

**Conflicts of Interest:** S.C., L.G., A.G., G.F.S., and A.D., declare no competing interest; T.P. and P.S. are employed by GVM Care & Research; D.M. and A.C. by Eta-Beta S.r.l. and F.S.; and A.M. by Water Team S.r.l. Water Team S.r.l. provided assistance and provision of the WTP 828 disinfectant and Eta Beta S.r.l. provided technical assistance for disinfection treatment.

**Ethics Approval and Consent to Participate:** Not applicable.

#### **Consent for Publication:** Not applicable.

**Availability of Data Materials:** The datasets generated and analyzed during the study are not publicly available due to ongoing further analysis on the data and protected by hospital privacy policies. The corresponding authors can response to any further questions about them.
