Surface-Modified Biopolymer Microparticles: A Potential Surrogate for Studying Legionella pneumophila Attachment to Biofilms in Engineered Water Systems

Despite numerous legionellosis outbreaks attributed to contaminated engineered water systems (EWSs), no suitable surrogate has been established for studying Legionella pneumophila in the EWSs. In this study, we developed a novel biopolymer surrogate by using DNA-encapsulated, amino acid-modified alginate-calcium carbonate microparticles. The surrogate mimicked L. pneumophila's size, rod shape, surface charge, and hydrophobicity. Preliminary proof-of-concept validations were conducted with the surrogate and L. pneumophila in laboratory flow-through biofilm bioreactor experiments with and without chlorine. The 2 entities displayed similar attachment/detachment magnitudes and kinetics to/from Pseudomonas f luorescens biofilms grown on stainless steel piping material. Their relative concentrations and peak attachment values were within the same orders of magnitude, and both exhibited slower attachment than detachment processes. Compared with the experiments without chlorine, surrogate and L. pneumophila biofilm attachment was significantly reduced in the presence of chlorine. P. f luorescens biofilm formation was not affected by exposure to the surrogate microparticles that were made of biocompatible materials. The promising results from our study suggest that further validations of this new surrogate are warranted. It may create new pathways for investigating L. pneumophila mobility and persistence in EWSs, which will facilitate better control of legionellosis risks.

Automated summary

A novel biopolymer surrogate mimicking Legionella pneumophila was developed and tested in laboratory experiments, showing similar behavior to Pseudomonas fluorescens. The surrogate and L. pneumophila biofilm attachment was significantly reduced in the presence of chlorine, indicating potential for better control of legionellosis risks.