Beyond the planktonic MIC: imaging biofilm-antimicrobial encounters

Abstract

Chronic bacterial infection is largely a biofilm problem, yet most antimicrobials are evaluated in planktonic suspension. Standard assays - MIC, time-kill, CFU, crystal-violet - measure bulk endpoints in geometries unlike a mature biofilm, averaging away the depth-stratified dynamics that determine outcome. This is a four-dimensional measurement problem, reducible to four questions: where an antimicrobial goes, where it kills, what it does to the matrix, and whether the community reassembles. We reorganize the imaging landscape along two orthogonal axes - temporal (3D static versus 4D live) and contrast (label-based versus label-free) - identifying a live, label-free, four-dimensional quadrant best aligned with them, though several members are not yet demonstrated for mature-biofilm 4D. The unexploited combinations within it define the opportunity to move beyond the planktonic MIC.