Salmonellosis- Food Infection and Food Poisoning by Salmonella

Salmonella is a genus of bacteria that belongs to the family Enterobacteriaceae and causes various diseases in humans and animals, such as gastroenteritis, typhoid fever, and paratyphoid fever. Salmonella infections are usually transmitted by consuming contaminated food or water, or by contact with infected animals or people. Salmonella can survive in a wide range of environmental conditions, such as low pH, high temperature, and bile salts.

The name Salmonella comes from Daniel Elmer Salmon (1850-1914), a U.S. veterinary surgeon who was the head of the Bureau of Animal Industry, a division of the U.S. Department of Agriculture. In 1885, he and his assistant Theobald Smith isolated the first strain of Salmonella from the intestine of a pig that died of hog cholera. They named it Salmonella choleraesuis, after the disease and the host animal.

However, Salmonella was actually discovered earlier by other scientists who did not recognize its significance or did not name it properly. In 1879, Karl Joseph Eberth observed rod-shaped bacteria in the spleen and lymph nodes of typhoid patients, but he could not grow them in pure culture. In 1880 and 1881, he published his findings and suggested that these bacteria were the cause of typhoid fever. His discovery was confirmed by Robert Koch and other bacteriologists in Germany and England.

The genus Salmonella now comprises two species: Salmonella enterica and Salmonella bongori. S. enterica is further divided into six subspecies that include over 2,600 serotypes based on their antigenic variations. S. enterica subsp. enterica contains most of the human pathogens, such as S. Typhi, S. Paratyphi, S. Enteritidis, and S. Typhimurium. S. bongori is mainly found in cold-blooded animals and rarely causes disease in humans.

Salmonella has been responsible for many outbreaks and epidemics throughout history, such as typhoid fever in ancient Greece and Rome, the Great Plague of Athens in 430 BC, the Plague of Justinian in 541 AD, and the Irish Famine Fever in 1846-1849. In modern times, Salmonella has caused foodborne illnesses associated with poultry, eggs, meat, dairy products, fruits, vegetables, spices, chocolate, peanut butter, and pet food.

Salmonella remains a major public health problem worldwide, especially in developing countries where sanitation and hygiene are poor. According to the World Health Organization (WHO), there are an estimated 93.8 million cases of salmonellosis and 155,000 deaths annually. Typhoid fever alone affects about 21 million people and kills about 200,000 people every year.