Fig. 1

Overview of the method. Carboxyl-coated paramagnetic nanoparticles are incubated with bacteria for 30 min with shaking (1). The paramagnetic nanoparticle-labelled Salmonella were then used to infect the human macrophage like cell line THP-1. The internalization of the bacteria is synchronized by a short centrifugation step (2). Internalized Salmonella establish an intracellular SCV (3). At different time points, macrophage are lysed using a mild detergent containing 2% sucrose solution (4), and the bacteria are recovered by application of a magnetic field (5). The recovered bacteria are then analysed by standard methods such as immunofluorescense and Western blotting for the presence or absence of standard SCV markers