A trickling biofilm chamber to investigate the survival of <i>Legionella pneumophila</i> in evaporative cooling systems

As biofilms are a crucial factor in the proliferation of <i>Legionella pneumophila</i> in evaporative cooling systems (ECS), the impact of biocides on <i>L. pneumophila</i> containing biofilms in ECS needs to be evaluated by cultivation-independent methods. Therefore, a trickling biofilm chamber that simulates the spraying of process water was developed. Through this setup, the cultivation of <i>Legionella</i>-containing biofilms was possible. To demonstrate a potential application of the biofilm chamber, experiments using oxidizing and non-oxidizing biocides were conducted. Differences in cell survival were observed, alongside variations in the efficacy of culture and flow cytometry as analytical methodologies for assessing both intact and total cell populations. These findings also highlight the benefits of flow cytometry as a culture-independent analytical approach. This proof-of-principle study illustrates the need of the biofilm chamber for conducting experiments related to biofilm growth and biocide impact.