Microbial Biofilms: Consequences For Health

MICROBIAL BIOFILMS: CONSEQUENCES FOR HEALTH

Introduction

Traditionally, microbiologists have grown bacteria as suspension cultures in rich media, in order to optimize cell yield. This planktonic mode of growth also became part of the standard assay on which all existing antimicrobials were selected and developed, and continues to be the basis for the selection of antimicrobials for specific patient treatment. We now recognize that in most environments, including our bodies, bacteria typically exist as adherent microcolonies termed biofilms, which afford bacteria a number of growth advantages including an inherent lack of susceptibility to antimicrobials. This antimicrobial tolerance differs from classical genetic resistance in that this reduced susceptibility disappears when the biofilm is returned to planktonic growth. Biofilm tolerance is multifactorial, which includes the spatial and structural parameters of the biofilm as well as the increased phenotypic diversity within the biofilm population. Biofilms are believed to be associated with approximately 60% of human infections including chronic, recurrent and devicerelated infections, therefore treatment of biofilm infections has become an important focus in modern medicine. As planktonic susceptibility testing, via the minimal inhibitory concentration (MIC) test, provides little guidance in the selection of antimicrobials to treat biofilms, a change in paradigm is required to determine appropriate treatment of biofilms and for the discovery of nextgeneration antimicrobials.