Salmonella Typhimurium infection of a human epithelial cell

Salmonella, or salmonellosis, is a well-known foodborne disease caused by the bacteria Salmonella. Over 2500 species of Salmonella have been discovered worldwide. Almost all species are pathogenic, causing illnesses varying in severity from diarhoea to typhoid fever. One species, Salmonella typhimurium, is shown in this image. S. typhimurium causes symptoms including stomach cramps, diarrhoea, vomiting and nausea, and if left untreated, death in the young, elderly, and immunocompromised. Following ingestion, Salmonella travels to the intestine. Here, it uses a specialised mechanism called the Type III secretion system to inject proteins into the epithelial cells lining the gut. As seen in this image, this disrupts the cytoskeleton of the cell and causes outward ruffling of the membrane. The bacterium is engulfed by these ruffles and dragged into the host cell. S.typhimurium length is approximately 2-3 micrometers.