Milieu matters: Anin vitrowound milieu to recapitulate key features of, and probe new insights into, polymicrobial biofilms

Abstract

Bacterial biofilms are a major cause of delayed wound healing. Consequently, the study of wound biofilms, particularly in host-relevant conditions, has gained importance. Most in vitro biofilm studies employ refined laboratory media to study biofilms, conditions that are not relevant to the infection state. To mimic the wound milieu, in vitro biofilm studies often incorporate serum or plasma in growth conditions, or employ clot or matrix-based biofilm models. While incorporating serum or plasma alone is a minimalistic approach, the more complex in vitro wound models are technically demanding, and poorly compatible with standard biofilm assays. Based on previous reports of clinical wound fluid composition, we have developed an in vitro wound milieu (IVWM) that includes, in addition to serum (to recapitulate wound fluid), matrix elements and biochemical factors. In comparison with Luria-Bertani broth and Fetal Bovine Serum (FBS), the IVWM was used to study planktonic growth and biofilm features, including interspecies interactions, of common wound pathogens, Staphylococcus aureus and Pseudomonas aeruginosa. We demonstrate that the IVWM recapitulates widely reported in vivo biofilm features such as metabolic activity, increased antibiotic tolerance, 3D structure, and interspecies interactions for single- and co-species biofilms. Further, the IVWM is simple to formulate, uses laboratory-grade components, and is compatible with standard biofilm assays. Given this, it holds potential as a tractable approach to study wound biofilms under host-relevant conditions.

A Synthetic Polymicrobial Community Biofilm Model Demonstrates Spatial Partitioning, Tolerance to Antimicrobial Treatment, Reduced Metabolism, and Small Colony Variants Typical of Chronic Wound Biofilms

“…Numerous in vitro models have been developed for the study of chronic wound biofilms to improve translation into the clinical environment (see [ 1 , 7 , 8 ] for thorough reviews). Most rely on modifications made to salient static biofilm models to incorporate elements that better mimic the host environment, including simulated wound fluids and three-dimensional tissue-like matrices.…”