Legionella pneumophila in health-care setting: sensitivity to biocidal treatments in mono- and multi-species biofilms

ABSTRACT There is now proof that some Legionella pneumophila outbreaks in health-care setting are related to the presence of biofilms, microbial consortium capable to induce partial resistance against many commonly used biocides. The aim of this study was to evaluate if the susceptibility of L. pneumophila to bronopol, chlorhexidine and silver ions can be affected by coexisting aquatic bacteria (Pseudomonas aeruginosa, Pseudomonas putida and Stenotrophomonas maltophilia) in sessile form. The results show that the sensitivity could be influenced by the presence of a mixed flora: the bacterial counts of L. pneumophila were reduced more effectively in multi-species than in mono-species biofilms.