title: Determination of antibiotic EC50 using a zero-flow microfluidic chip based growth phenotype assay.
abstract: Current existing assay systems for evaluating antimicrobial activity suffer from several limitations including excess reagent consumption and inaccurate concentration gradient preparation. Recently, microfluidic systems have been developed to provide miniaturized platforms for antimicrobial susceptibility assays. However, some of current microfluidic based assays require continuous flows of reagents or elaborate preparation steps during concentration preparation. In this study, we introduce a novel microfluidic chip based growth phenotype assay that automatically generates a logarithmic concentration gradient and allows observing the growth of pathogenic bacteria under different concentrations of antibiotics in nanoliter batch culture reactors. We chose pathogen bacterium Pseudomonas aeruginosa as a model strain and evaluated the inhibitory effects of gentamicin and ciprofloxacin. We determined the EC50 values and confirmed the validity of the present system by comparing the EC50 values obtained through conventional test tube method. We demonstrated that the EC50 values acquired from present assay are comparable to those obtained from conventional test tube cultures. The potential application of present assay system for investigating combinatorial effects of antibiotics on multidrug resistant pathogenic bacteria is discussed and it can be further used for systematic evaluation of antifungal or antiviral agents.
authors.affiliation: Materials Research and Education Center, Department of Mechanical Engineering, Auburn University, Auburn, AL, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Dai
authors.affiliation: Department of Biological Sciences, Auburn University, Auburn, AL, USA.
authors.forename: Sang-Jin
authors.initials: SJ
authors.lastname: Suh
authors.affiliation: Materials Research and Education Center, Department of Mechanical Engineering, Auburn University, Auburn, AL, USA.
authors.forename: Morgan
authors.initials: M
authors.lastname: Hamon
authors.affiliation: Materials Research and Education Center, Department of Mechanical Engineering, Auburn University, Auburn, AL, USA. hongjon@auburn.edu.|Department of Bionano Engineering, Hanyang University, Ansan, Korea. hongjon@auburn.edu.
authors.forename: Jong Wook
authors.initials: JW
authors.lastname: Hong
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004867:Equipment Design; D008826:Microbial Sensitivity Tests / Q000295:instrumentation* / Q000379:methods*; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D011550:Pseudomonas aeruginosa / Q000187:drug effects
chemical_list: D000900:Anti-Bacterial Agents
keywords: Antibiotic susceptibility; Growth phenotype assay; Half maximal effective concentration (EC50); Logarithmic concentration gradient; Microfluidics