Salmonella is the genus name for a group of bacteria that consists of two species; Salmonella bongori and Salmonella enteric. Salmonella enterica is responsible for the majority of Salmonella infections in warm-blooded animals, according to the article "Characterization of Salmonella enterica Subspecies I Genovars by Use of Microarrays" published in the Journal of Bacteriology. Salmonella enteric is further divided into six sub-species, each with hundreds of different serotypes. Three serotypes of S.enterica subspecies enterica--typhimurium, enteritidis and Newport--are responsible for over 50 percent of all human infections, as reported by the Journal of Bacteriology.
Salmonella bacteria are rod-shaped gram-negative bacteria. Gram-negative bacteria do not retain the crystal violet dye used in the gram staining method due to the fact that they have cell walls that are thin. Gram-negative bacteria are often harmful to a host, which is the case for many of the Salmonella bacteria.
Salmonella bacteria are between 2 and 5 micrometers long and 0.7 to 1.5 micrometers in diameter. They have flagella, which are tail-like projections made of proteins that help the bacteria to move.
Salmonella bacteria live in the intestines of both cold and warm blooded animals. The bacteria can be found throughout the natural environment, including soil and water, that has been contaminated with nimal excrement. Although the bacteria cannot multiply outside of the host digestive tract, they can live for several weeks in water and several years in soil when conditions such as humidity, pH and temperature are favorable.
Salmonella bacteria are zoonotic, meaning they can be transmitted from humans to animals or from animals to humans. The mode of transmission is the fecal-oral route meaning that you can become infected by ingesting food or water that has been contaminated with fecal matter containing the bacteria. Proper food thawing and handling techniques along with proper sanitation and hand-washing can help to prevent salmonella infections.
There are several different diseases that can be caused by Salmonella bacteria. Gastroenteritis, more commonly known as food poisoning, is the most common and is caused by Salmonella enteritidis. This form of salmonellosis usually begins 12 to 72 hours after ingesting the contaminated food and lasts from four to seven days according to the Centers for Disease Control and Prevention. Symptoms include diarrhea, fever and abdominal cramps which usually subside on their own without medical treatment. The bacteria can cross from the intestines into the bloodstream causing serious illness or even death if not treated with antibiotics.
Typhoid fever, caused by Salmonella typhi, is also transmitted through contaminated food and water but causes a more serious systemic (throughout the body) infection. Symptoms include fever, sweating, gastroenteritis, diarrhea and rash. If left untreated, the fever can last for weeks or even month causing complications that can result in death.