Current Status of In Vitro Models and Assays for Susceptibility Testing for Wound Biofilm Infections

Abstract

Biofilm infections have gained recognition as an important therapeutic challenge in the last several decades due to their relationship with the chronicity of infectious diseases. Studies of novel therapeutic treatments targeting infections require the development and use of models to mimic the formation and characteristics of biofilms within host tissues. Due to the diversity of reported in vitro models and lack of consensus, this review aims to provide a summary of in vitro models currently used in research. In particular, we review the various reported in vitro models of Pseudomonas aeruginosa biofilms due to its high clinical impact in chronic wounds and in other chronic infections. We assess advances in in vitro models that incorporate relevant multispecies biofilms found in infected wounds, such as P. aeruginosa with Staphylococcus aureus, and additional elements such as mammalian cells, simulating fluids, and tissue explants in an attempt to better represent the physiological conditions found at an infection site. It is hoped this review will aid researchers in the field to make appropriate choices in their proposed studies with regards to in vitro models and methods.

Keywords: biofilms; chronic infections; in vitro models; viability assays.

Figure 1

Number of publications per year with the word biofilms in the title of the article searched by Google Scholar. The labels indicate the dates where the evidence of biofilms in new tissues was published.

Figure 2

Stages of biofilm development: (1) Reversible attachment, (2) Irreversible attachment, (3) Maturation 1, (4) Maturation 2, and (5) Dispersion [76].

Figure 3

The heterogeneous susceptibility of bacterial biofilms to antibiotics [88].

Figure 4

Different systems for static growth of biofilm. (A) Colony biofilm model, (B) Calgary device lid, and (C) round bottom 96-well plate.

Figure 5

General schematics of the components of flow cell systems for biofilm formation.

Figure 6

General schematics of the components of biofilm reactors.