Mechanical properties of Staphylococcus aureus and Pseudomonas aeruginosa dual-species biofilms grown in chronic wound based models*

Biofilms are frequently found in oral, respiratory, and chronic wound infections caused by various diseases. These biofilms are typically polymicrobial, and collaborative interactions among bacteria are linked to their persistence. One common pair of species that form polymicrobial biofilms in chronic wounds are Staphylococcus aureus and Pseudomonas aeruginosa. Multiple studies have demonstrated how these species synergize to enhance colonization and chronicity, defying effective treatments.

This study builds on previous work, investigating how wound bed environment aids in the formation of polymicrobial biofilms, affects their mechanical stability, and ultimately impacts debridement. We hypothesize that collagen, a primary component in wound extracellular matrix, mediates between S. aureus and P. aeruginosa allowing formation of more robust polymicrobial biofilms. Using microrheology and colony counting, we have observed that biofilms grown in cultures that include collagen and secondary wound proteins form polymicrobial biofilms when both bacteria are initially present in culture. Furthermore, these biofilms are more elastic and stiffer in comparison to single species biofilms grown in identical conditions. However, if collagen is absent or collagen is present without a secondary protein, a single species biofilm will form from an initial co‑culture.  These results indicate that the host environment plays an important role in mediating the formation of polymicrobial biofilms.