Microfluidic advances in phenotypic antibiotic susceptibility testing.

A strong natural selection for microbial antibiotic resistance has resulted from the extensive use and misuse of antibiotics. Though multiple factors are responsible for this crisis, the most significant factor - widespread prescription of broad-spectrum antibiotics - is largely driven by the fact that the standard process for determining antibiotic susceptibility includes a 1-2-day culture period, resulting in 48-72 h from patient sample to final determination. Clearly, disruptive approaches, rather than small incremental gains, are needed to address this issue. The field of microfluidics promises several advantages over existing macro-scale methods, including: faster assays, increased multiplexing, smaller volumes, increased portability for potential point-of-care use, higher sensitivity, and rapid detection methods. This Perspective will cover the advances made in the field of microfluidic, phenotypic antibiotic susceptibility testing (AST) over the past two years. Sections are organized based on the functionality of the chip - from simple microscopy platforms, to gradient generators, to antibody-based capture devices. Microfluidic AST methods that monitor growth as well as those that are not based on growth are presented. Finally, we will give our perspective on the major hurdles still facing the field, including the need for rapid sample preparation and affordable detection technologies.