Ladder shaped microfluidic system enabling rapid antibiotic susceptibility testing with standardized concentration panel

Antibiotics are often prescribed before pathogens are identified and susceptibility to the prescribed drug is confirmed; laboratory results may take up to 3 days. Using rapid antibiotic susceptibility testing (AST) this timeline can be compressed. We designed a microfluidic ladder-based system that generates a twofold serial dilution of antibiotics comparable to current national and international standards. This consolidated design, with minimal handling steps, has cut down the time-to-result for AST from 16-20 h to 4-5 h. Our system has a 91.75 % rate of agreement with the commercial AST system for Gram-negative and Gram-positive bacterial isolates from canine urinary tract infections (UTI) tested against seven clinically relevant antibiotics. Overall, the system showed a matching rate of 92.71 % - 94.54 % with Gram-negative pathogens, and 85.00 % - 88.57 % with Gram-positive pathogens with no statistical difference between the pathogens or antibiotics. We also tested bacteria filtered directly from urine samples, potentially reducing the total sample-to-result time from 2-3 days to 4 hours.