Application of an optically induced dielectrophoresis (ODEP)-based microfluidic system for the detection and isolation of bacteria with heterogeneity of antibiotic susceptibility

Different levels of antibiotic resistance reside in a bacterial clone (heteroresistance) is regarded as an important cause leading to development of superbugs and treatment failure of infectious diseases. However, phenotypical detection of bacterial heteroresistance is not available in current clinical practice or by present analytical tools. To address this issue, we developed an optically induced dielectrophoresis (ODEP)-based microfluidic system capable of detecting bacterial heteroresistance and isolating minor resistant strain within a bacterial clone. The working principle is based on the different levels of ODEP force exerted on the bacteria with different degrees of viability, which was resulted from different degrees of antibiotic resistance. We designed and fabricated an ODEP-based microfluidic system, and used standard bacterial strains, namely E. coli ATCC 35218 (antibiotic resistant strain) and E. coli ATCC 25922 (antibiotic susceptible strain) to prove the proposed concept. After treated with ampicillin for 1 h, we demonstrated that both bacterial strains could be isolated with high recovery rate up to 98.07 %. Moreover, we mixed E. coli ATCC 35218 and E. coli ATCC 25922 with a variety of heterogeneous ratios to simulate heteroresistance. The ratio of the resistant strain could be significantly elevated from the original 1 % to approximately 67 % after manipulated by the proposed system. Overall, in the proof-of-concept study we demonstrated that the ODEP-based microfluidic system could effectively detect and isolate high resistant bacterial strain from a clone with heteroresistance. The ability of detecting phenotypic heteroresistance renders it a promising tool for further clinical applications or fundamental studies.