New tools to monitor infection and biofilms in .

Introduction: Antimicrobial resistance is a growing health problem. Pseudomonas aeruginosa is a pathogen of major concern because of its multidrug resistance and global threat, especially in health-care settings. The pathogenesis and drug resistance of depends on its ability to form biofilms, making infections chronic and untreatable as the biofilm protects against antibiotics and host immunity. A major barrier to developing new antimicrobials is the lack of biofilm models. Standard microbiological testing is usually performed using planktonic bacteria, without representation of biofilms, reducing translatability. Here we develop tools to study both infection and biofilm formation by to accelerate development of strategies targeting infection and pathogenic biofilms.

Methods: Biofilms were quantified in vitro using Crystal Violet staining and fluorescence biofilm assays. For in vivo assays, were infected with strains. Pathogenicity was quantified by measuring healthspan, survival and GFP fluorescence. Healthspan assays were performed using the WormGazerTM automated imaging technology.

Results: Using the nematode and reporters combined with imaging we show that fluorescent P. aeruginosa reporters that form biofilms can be used to visualize tissue infection. Using automated tracking of movement, we find that that the timing of this infection corresponds with a decline in health endpoints. In a mutant strain of P. aeruginosa lacking RhlR, a transcription factor that controls quorum sensing and biofilm formation, we find reduced capacity of P. aeruginosa to form biofilms, invade host tissues and negatively impact healthspan and survival.

Discussion: Our findings suggest that RhlR could be a new antimicrobial target to reduce biofilms and virulence in vivo and could be used to more effectively screen for new drugs to combat antimicrobial resistance.