Date of Award


Degree Type


Degree Name

Master of Science (MS)


Biomedical and Chemical Engineering


Dacheng Ren

Subject Categories



Antibiotic resistance has been on the rise and poses major threats to public health. Bacteria develop multidrug resistance through various mechanisms such as mutated or modified antibiotic target site, modification of antibiotic molecules, reduction of antibiotic penetration through bacterial cell membranes and extrusion of drug molecules by efflux pumps. Increasing evidence indicates that antibiotic permeability is a major barrier hindering microbial control. However, a robust and rapid screening method to quantitatively determine the penetration of candidate agents through bacterial membranes is still missing. To address this challenge, we recently developed a high throughput method for quantifying membrane penetration of Gram-negative bacteria by optimizing treatment conditions to lyse the inner and outer membranes separately. In this study, we further improved the assay throughput and evaluated the penetration of ciprofloxacin (CIP) and tobramycin (TOB) into Escherichia coli MG1665 and Pseudomonas aeruginosa PAO1. With optimized experimental conditions, it was found that cytoplasmic membrane is a critical barrier to CIP and TOB penetration in both species tested. The results were corroborated by P. aeruginosa PAO1 efflux pump mutants. This new method can be used in future studies to identify novel antimicrobials and inhibitors of bacterial efflux pumps.


Open Access

Included in

Engineering Commons



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