(425a) High Throughput Screening the Effects of Antibiotic Delivery Rates On Biofilm Antibiotic Resistance

Bacterial biofilms are a heterogeneous
community of bacteria distributed in a matrix comprised primarily of hydrated
polysaccharides. Compared to bacteria dispersed in liquid cultures,
biofilm-associated bacteria can tolerate antimicrobial concentrations orders of
magnitude higher. Phenotypic differentiation and lateral gene transfer of
antibiotic resistance genes in biofilm promotes antibiotic resistance in
biofilm. High throughput technologies have been widely used to screen effective
antimicrobial concentrations, where biofilms are usually exposed in constant
antibiotic concentration or fixed mass of antibiotic. However, biofilms in
nature are usually challenged with changing micro-chemical environment due to
diffusion limitations and periodic dosing regimes. The effect of antimicrobial
delivery rates on antimicrobial resistance in biofilms is infrequently
measured. Here we introduce a novel microfluidic approach for high-throughput
screening of respiration inhibition of bacteria in a biofilm
array morphology (Figure 1).  The device
geometry and operating conditions allow antimicrobial concentrations and fluxes
to vary systematically and predictably with space and time. In effect, one
experiment can screen biofilm respiratory responses to many different
antimicrobial delivery rates. Our results demonstrate the effect of antibiotic
concentration on biofilm respiration inhibition.  Biofilm experiencing slowly increasing
antibiotic concentrations can withstand higher total concentrations compared
with bacteria exposed to rapidly increasing concentrations.  We anticipate our approach can be used as a
starting point for investigating the effects of antimicrobial delivery rate on
development of antimicrobial resistance in biofilms. Longer term, the work may
help direct clinical work on effective antimicrobial therapies for the
treatment of biofilm-associated diseases.

Figure 1:

Figure 1. Schematic
of the microfluidic diffusion device with biofilm array. (a) The
microfluidic device consists of oxygen sensing film on a glass slide, a PDMS
layer with a biofilm array patterned on top, and a PDMS microfluidic device
bonded on top. (b) Photograph of an array enclosed in a microfluidic diffusion
device, with red dye loaded in a perimeter source well.