Why are Bacterial Biofilms so Tolerant to Antimicrobial Treatment?
Matt Parsek, University of Washington, Seattle, USA
Surface-attached bacteria living in communities called biofilms cause many human chronic infectious diseases. Biofilm bacteria are less susceptible to antibiotic treatment and clearance by the host immune system than suspended, free-floating bacteria of the same species. Since biofilms haves been linked to chronic disease, several researchers have attempted to identify the molecular basis for their inherent tolerance to antimicrobials. A few decades of research collectively suggest that biofilm antimicrobial tolerance is probably multifactorial. Slow growing subpopulations, the presence of a protective extracellular matrix, and a biofilm-specific physiology have all been shown to contribute to a biofilm’s reduced susceptibility to antibiotics. However, the heterogeneity seen in bacteria present in a biofilm is a major obstacle in their study. Microbiology is a discipline that has developed using shaken liquid cultures that produce homogenous populations of bacteria. Biofilm microbiologists are struggling to develop new tools to study heterogenous populations of bacteria such as biofilms. I will share some of my own work with the pathogenic species of bacteria, Pseudomonas aeruginosa. P. aeruginosa causes chronic lung infections in people suffering from the disease cystic fibrosis. In the CF airways, P. aeruginosa is thought to produce large cellular aggregates with attributes of biofilm communities. I will discuss our work relating P. aeruginosa surface-sensing and its relationship to aminoglycoside sensitivity.