Infection of Epithelial Cells With Salmonella enterica - Bacterial Pathogenesis: Methods and Protocols - page 190

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Infection of Epithelial Cells With Salmonella enterica
Olivia Steele-Mortimer
Summary
Salmonella enterica serovars cause a variety of diseases ranging from self-limiting
gastroenteritis to severe systemic infections. Virulence of these facultative intracellular
pathogens is dependent on their ability to invade and replicate within non-phagocytic cells,
and cultured epithelial cell systems have been used extensively to dissect the molecular
mechanisms involved. For efficient invasion in vitro , the bacterial cell growth conditions as
critical since the invasion associated type III secretion system (T3SS1) must be expressed
and functional. The ability of Salmonella to invade, and replicate within, epithelial cells can
be easily assessed using a gentamicin protection assay or immunofluorescence microscopy.
Here, the protocols used in our laboratory are described in detail.
Key Words: Bacteria; immunofluorescence; intracellular; invasion; type III secretion.
1. Introduction
The more than 2500 serovars of Salmonella enterica are genetically highly
similar yet tend to have highly specific host and virulence characteristics (1) .
For example, S. enterica serovar Typhimurium is one of the most common
causes of gastroenteritis in humans but causes a systemic “typhoid-like” disease
in susceptible mice and is used as an animal model for typhoid fever. Multiple
virulence factors contribute to pathogenesis including two sets of bacterial
effector proteins that are delivered directly into the host cell by the type III
secretion systems, T3SS1 and T3SS2 (2) . T3SS1 effectors are translocated
across the plasma membrane and act cooperatively to induce actin rearrange-
ments and membrane ruffling, resulting in the internalization of Salmonella
into a membrane-bound vacuole known as the Salmonella -containing vacuole