General Information: This pathogenic strain of Salmonella typhi was isolated in the early 1970s. It contains no multidrug resistance plasmids and has been used for vaccine development. This serovar is a human-specific organism that causes the life-threatening illness Typhoid fever which is acquired by coming into contact with contaminated food or water. Annually, 17 million people are infected, with 600,000 fatalities, mostly in developing countries. It contains multiple fimbrial operons that may be used to create extracellular appendages for attachment and entry into host intestinal epithelial cells. Causes enteric infections. This group of Enterobactericiae have pathogenic characteristics and are one of the most common causes of enteric infections (food poisoning) worldwide. They were named after the scientist Dr. Daniel Salmon who isolated the first organism, Salmonella choleraesuis, from the intestine of a pig. The presence of several pathogenicity islands (PAIs) that encode various virulence factors allows Salmonella spp. to colonize and infect host organisms. There are two important PAIs, Salmonella pathogenicity island 1 and 2 (SPI-1 and SPI-2) that encode two different type III secretion systems for the delivery of effector molecules into the host cell that result in internalization of the bacteria which then leads to systemic spread.