(102e) Dielectrophoretic Separation of Microorganisms Based On Speciation and Life-Cycle Stage

Micro-organisms are usually present in heterogeneous samples that are spread over a range of developmental lifecycles and species type. Since antibiotic treatments are influenced by interactions across species type and developmental lifecycle stages, the development of antibiotic treatments can greatly benefit from techniques capable of separating microbial samples based on developmental lifecycle stage and species type. Herein, we investigate the application of dielectrophoresis towards accomplishing such separations for infectious organisms, such as Cryptosporidium parvum, a water-borne pathogenic protozoan parasite [1] and Clostridium dificile, a bacterial species implicated within hospital infections [2]. In parallel to their dielectrophoretic separation on a microfluidic device with insulator constrictions [3], the magnitude and direction of the trapping force is measured through real-time tracking of the velocity profile of single microbial cells for computing their dielectric properties based on fitting the frequency response of the force to a standard shell model. In this manner, dielectric properties of the microbial species can be correlated to their phenotype to optimize conditions, such as medium conductivity, and applied field and frequency towards enabling more effective separations. The application of this methodology is presented towards separating and characterizing the heterogeneous alterations of Cryptosporidium parvum after contact with disinfectants for quantifying the integrity of sporozoites and the oocyst wall to a high degree of sensitivity, in spite of the heterogeneous nature of their modification. Similarly this separation methodology is used to study the effect of interactions across species type (toxic versus non-toxic) and developmental lifecycle stages (spore versus vegetative) on the efficacy of antibiotic treatments on Clostridium dificile.

[1] Chen, X.M., et al., “Cryptosporidiosis”. N Engl J Med, 2002. 346(22): p. 1723-31.

[2] M. Rupnik, M. H. Wilcox, D. N. Gerding. “Clostridium dificile infections: new developments in epidemiology and pathogenesis, Nature Review(2009), 7, 526-536.

[7] Swami, N.; Chou, C.-F.; Ramamurthy, V.; Chaurey, V. Enhancing DNA hybridization kinetics through constriction-based. Lab on a Chip 2009, 9, 3212–3220.