Some bacteria of the species Salmonella -- of which almost 2500 different "serotypes" have been identified -- can cause infections in people. Salmonella enterica subtype typhi, also known as Salmonella typhi, and related Salmonella bacteria are the cause of enteric or typhoid fever. Salmonella typhi infections are seen only in people, and it is possible to vaccinate against it.
Other Salmonella bacteria are often found in animal-based foods, such as poultry, eggs, beef, and dairy products. Since the bacteria grow well in animal intestines, and an animal may have Salmonella bacteria in its intestines without symptoms, plant-based foods may also be contaminated with Salmonella. It is also possible for people to be carriers of Salmonella without having any symptoms, although they will excrete the bacteria in their stools. However, many people who eat Salmonella-contaminated foods develop gastroenteritis ("stomach flu"). The diarrhea and other symptoms are actually produced by toxins produced by the bacteria; cooking food thoroughly will destroy the toxins as well as the bacteria.
Salmonella "food poisoning" is seen often in developing countries where sanitation is poor. However, it is also seen fairly frequently in developed countries, whether due to food contaminated in manufacturing or food contaminated when handled by a preparer who carries Salmonella without having symptoms himself. In January, 2009 many people in the United Stated developed Salmonella gastroenteritis, and a few people died, due to contaminated peanut butter and other peanut products from a single US factory. The bacteria identified turned out to be Salmonella serotype Typhimurium, one of the strains that causes typhoid fever.
Symptoms of Salmonella infection may include the symptoms of gastroenteritis, including fever, diarrhea, and abdominal cramps. In some people Salmonella bacteria can be found in the bloodstream, and Salmonella meningitis and osteomyelitis (infection of bone tissue) can also occur.
We usually do not treat people with non-typhoid Salmonella who have no symptoms, or who have gastroenteritis without complications. Giving antibiotics in these cases doesn't seem to help people recoved faster and may actually make these people excrete Salmonella bacteria for a longer time. We will, however, treat babies (3 months old or younger), patients who have Salmonella bacteria in their blood (even if they are not septic, and others who may be more likely to develop meningitis, septis, or other serious infections, including people with cancer, HIV infections, chronic problems with their digestive systems, and others whose immune systems may not be working up to par. The antibiotics we use include ampicillin and trimethoprim-sulfamethoxazole. In some areas the local Salmonella has become resistant to these antibiotics, and so we have to use other agents.
The best way to treat Salmonella infections is to prevent them in the first place. Raw animal-based foods, including eggs, should be cooked thoroughly before eating. Other foods should be cooked as well, especially during an outbreak. If a particular food or food source is known to be contaminated, avoid it: for the peanut-related Salmonella outbreak, the US Centers for Disease Control and Prevention and the US Food and Drug Administration recommended that people get rid of any foods that have been recalled because they might have contained peanut products from the source factory.