The present invention provides methods for utilizing a form of optimized suspension culture to examine the infectivity of pathogenic organisms and agents in human cells and tissues. Also provided are methods using a rotating wall vessel to predict chemosensitivity of cells and tissues to toxins and chemotherapeutic agents. These culture conditions potentiate spatial colocalization and three-dimensional assembly of individual cells into large aggregates which more closely resemble the in vivo tissue equivalent. In this environment, dissociated cells can assemble and differentiate into macroscopic tissue aggregates several millimeters in size. These culture conditions allow for better cellular differentiation and formation of three-dimensional cellular aggregates, more efficient cell-to-cell interactions, the in in vivo-like exchange of growth factors and greater molecular scaffolding facilitating mechanical stability for cells. The suspension culture system offers a new approach for studying microbial infectivity from the perspective of the host-pathogen interaction and also for analyzing chemosensitivity to toxins and chemotherapeutic agents.