Peering into the matrix: A look at biofilms and their inherent antibiotic resistance

Biofilms are increasingly being regarded as the predominant form of bacterial growth in natural settings. These structures consist of bacterial cells immobilized at a surface and encased in a self-produced matrix of extracellular polymeric substances. In clinical settings, biofilms are the cause of persistent infections that are difficult to clear through the action of the host immune system. Biofilm-encased cells are also associated with increased levels of antibiotic resistance compared to their planktonic counterparts. The result is increased morbidity and mortality when biofilms are associated with disease. In this review, the focus of discussion will be the various mechanisms of antibiotic resistance common to biofilms and the role these mechanisms play in the pathogenesis of major clinically-relevant microorganisms. Antibiotic penetration, altered microenvironments, phenotypic variation, and adaptive resistance mechanisms are all key players in the development of antibiotic resistance in bacterial biofilms. Though the relative significance of each individual mechanism varies, when combined they confer extensive protection to the biofilm’s cellular populations. Keywords: biofilms; antibiotic resistance (mechanisms of); clinical applications; disease; antibiotic penetration; altered microenvironments; phenotypic variation; adaptive resistance; revie