The effectiveness and role of phages in the disruption and inactivation of clinical P. aeruginosa biofilms

Biofilms of P. aeruginosa are known to be resilient forms of survival of this opportunistic pathogen, both within the host and in natural or engineered environments. This study investigated the role of phages in the disruption and inactivation of clinical P. aeruginosa biofilms by previously isolated phages. All seven tested clinical strains formed biofilms in 56-80 h. Four previously isolated phages were effective in disrupting the formed biofilms when applied at multiplicity of infection (MOI) of 10, where phage cocktails had equivalent or worse perfor-mance than single phages. Phage treatments reduced the biofilms' biomass (cells and extracellular matrix) by 57.6-88.5% after 72 h of incubation. Biofilm disruption led to the detachment of 74.5-80.4% of the cells. The phages were also able to kill the cells from the biofilms, reducing the living cell counts by approximately 40.5-62.0% after a single treatment. A fraction of 24-80% of these killed cells were also lysed due to phage action. This study showed that phages can have a relevant role in disrupting, inactivating, and destroying P. aeruginosa biofilms, which can be used in the development of treatment processes to complement or replace antibiotics and/or disinfectants.