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Salmonellae Invasion Kinetics

Salmonella Typhimurium is a common cause of gastroenteritis in humans and also localizes to neoplastic tumors in animals. Invasion of specific eukaryotic cells is a key mechanism of Salmonella interactions with host tissues. Early stages of gastrointestinal cell invasion are mediated by a Salmonella type III secretion system, powered by the adenosine triphosphatase invC. The aim of this work was to characterize the invC dependence of invasion kinetics into disparate eukaryotic cells traditionally used as models of gut epithelium or neoplasms. Thus, a nondestructive real-time assay was developed to report eukaryotic cell invasion kinetics using lux+ Salmonella that contain chromosomally integrated luxCDABE genes. In standard gentamicin protection assays, bioluminescence from lux+ Salmonella correlated with recovery of colony-forming units of internalized bacteria and could be visualized by bioluminescence microscopy.
Figure 1
Comparison of colony-forming unit (CFU) recovery and bioluminescence (photon flux, in photons/second) from gentamicin protection assays using bioluminescent Salmonella that vary only by invC gene status. Invasion of Henle epithelial eukaryotic cells by bioluminescent Salmonella either with invC (wild type, invC+) or without invC (invC-) is shown. A representative pair of wells from the bioluminescence-based assay is shown with adjacent wells containing either invC+ (left well) or invC- (right well) luxCDABE+ Salmonella.
Figure 2
Microscopic detection of bioluminescence from luxCDABE+ Salmonella in eukaryotic cell cultures. Henle cell monolayers are shown either alone (left panels) or following inoculation with luxCDABE invC+ Salmonella (right panels). For each sample, images show the bioluminescence signal alone (top), the phase contrast (bottom), and a merged image of bioluminescence and phase contrast (middle). Within the merged image of the Henle cells inoculated with luxCDABE Salmonella, a box demarcates the image area enlarged in the upper right corner (inset). Yellow arrows outline a Henle cell; maximal intensity foci occur near or within eukaryotic cells.
Reference:	Flentie KN, Qi M, Gammon ST, Razia Y, Lui F, Marpegan L, Manglik A, Piwnica-Worms D, McKinney JS. Stably Integrated luxCDABE for Assessment of Salmonellae Invasion Kinetics. Mol Imaging 2008; 7(5): 222-33.	PubMed Link

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