Bacteria of the genus Salmonella account for the majority of food poisoning cases in the United States, with the Centers for Disease Control and Prevention (CDC) estimating 1.4 million cases annually. It is a rod-shaped, gram-negative, facultative anaerobe that infects a wide variety of organisms, from lizards to humans. The main feature of salmonella pathogenesis is the type III secretion system (TTSS), a needle-like multiprotein complex that delivers toxic proteins to host cells. One of these proteins, SopB, causes the diarrhea characteristic of salmonella disease.
Salmonella infection results in either typhoid fever (if the individual is infected by the typhi or paratyphi serovars) or gastroenteritis (if infected by the enterditis serovar). Typhoid fever was a potent killer prior to the development of modern antibiotics. The pathogen’s weaponization potential and the severe gastrointestinal symptoms it inflicts on the majority of infected individuals have led to its classification as a Category B biological threat by the CDC.
Salmonella is believed to have killed many famous historical figures, most notably Alexander the Great and Prince Albert, the husband of Queen Victoria. The pathogen was identified in 1885 by the American veterinarian Dr. Daniel E. Salmon, for whom the pathogen is named.
In 1898—a little over a decade after Salmon’s isolation of the choleraesuis strain from the intestine of a pig—British surgeon Almroth E. Wright developed an antityphoid inoculation. The first salmonella vaccine consisted of a heat-denatured bacterium, a rudimentary killed-whole-cell vaccine, which was successfully used during World War I to reduce the number of soldiers who died from enteric fever.3 Despite this, the disease was not deemed to have a cure until the discovery of antibiotics in the twentieth century.