Abstract
A biofilm is a multicellular consortium of surface associated microbes surrounded by a hydrated, extracellular polymer matrix. The biofilm matrix plays a critical role in preventing desiccation, acquiring nutrients, and provides community protection from environmental assaults. Importantly, biofilms are significantly more resistant to antimicrobials relative to their free-swimming counterparts. The level of antimicrobial tolerance is influenced by a number of factors, including genetic/adaptive resistance mechanisms, stage of biofilm development, and pharmacokinetics of the antibiotic. Here, we describe an in vitro microtiter-based assay to quantify the minimal bactericidal concentration for biofilms (MBC-B) for short exposure times (2 h). This exposure period is significantly shorter than standard over-night and 24-hour treatments described in traditional protocols. This assay was developed to approximate the time an antibiotic is available during a one-time treatment before it is metabolized, sequestered by host proteins, or digested.