Salmonella is a rod-shaped bacteria that is commonly contracted through contaminated foods. Ingestion can be easily prevented through sanitation, thorough cooking, and proper care of foods. Foods that are often contaminated with Salmonella include peanut butter, tomatoes, raw egg shells, etc. It enters into the digestive tract and travels to the intestines where it intrudes the mucosa on the intestinal walls and causes diseases and infections of the digestive tract.
Salmonella typhi is made up of two plasmids and a circular chromosome. There physical appearance is a thin, rod-shaped prokaryote with a flagella attatched at the end for movement.  Salmonella do not require oxygen in order for survival. The salmonella cells are able to withstand the digestive acids and processes performed by the human digestive tract and eventually end up in the intestines. They are able to make it through the mucosa of the intestine and are transported the liver and spleen. Most bacteria would be killed during this transportation whereas salmonella will survive and continue to multiply.
The most common habitat where salmonella thrives are poultry, red meat, and raw egg shells. Salmonella is commonly contracted throught contaminated water.
Most health services will advise you to cook and properly handle food in the kitchen to prevent disease-causing bacteria such as salmonella. Salmonella is one of the most common types of food poisoning that is recorded in the United States.
When salmonella is ingested in food, it passes through the body's digestive system. Once it reaches the small and large intestines, it intrudes the mucosa where it produces toxins. The affects on the body include diarrhea and ulceration. Once the bacteria has reached the intestinal tract, it multiplies rapidly and creates a colony. As a colony, in humans, it will commonly cause gastroenteritis. 
Causes and Treatments
The cause of salmonella ingestion is mainly through contaminated foods. Common foods that carry salmonella consist of tomatoes, raw egg shells, peanut butter, etc. There are, however, many different species of the salmonella bacteria. Salmonella Typhi is the common cause for typhoid fever. Typhoid fever induces many symptoms such as nausea, vomitting, fever and death. Salmonella is only able to intrude man's immune system and no other hosts have been discovered. 
Salmonella typhimurium is the most common species contracted by humans. Although not as severe as S. typhi, it causes symptoms such as diarrhea, nausea and vomitting, abdominal cramps, etc. The infection usually only lasts around seven days. 
In general, salmonella bacteria infects the intestinal tract and causes similar symptoms.
Treatments for a salmonella infection are unsettled amongst doctors. Some may prescibe antibiotics but others argue against it because of the fact that the bacterium are self-limited and antibiotics may even prolong the infection. 
Salmonella cells isolated from infected macrophrages.
- Salmonella Unknown Author. MicrobeWiki.
- Salmonella Ralph A. Giannella.
- Salmonella typhimurium Author. Publisher.
- Salmonella information
- How Are Salmonella Infections Treated? MedicineNet