Salmonella

Salmonella is a genus of rod-shaped (bacillus), gram-negative bacteria of the family Enterobacteriaceae. The two known species of Salmonella are Salmonella enterica and Salmonella bongori. S. enterica is the type species and is further divided into six subspecies that include over 2,650 serotypes. Salmonella was named after Daniel Elmer Salmon (1850–1914), an American veterinary surgeon. Salmonella species are non-spore-forming, predominantly motile enterobacteria with cell diameters between about 0.7 and 1.5 μm, lengths from 2 to 5 μm, and peritrichous flagella (all around the cell body, allowing them to move). They are chemotrophs, obtaining their energy from oxidation and reduction reactions, using organic sources. They are also facultative anaerobes, capable of generating adenosine triphosphate with oxygen ("aerobically") when it is available, or using other electron acceptors or fermentation ("anaerobically") when oxygen is not available. Salmonella species are intracellular pathogens, of which certain serotypes cause illness such as salmonellosis. Most infections are due to the ingestion of food contaminated by feces. Typhoidal Salmonella serotypes can cause foodborne illness as well as typhoid and paratyphoid fever and can be transferred only between humans. Typhoid fever is caused by typhoidal Salmonella entering the bloodstream then spreading throughout the body, invading organs, and secreting endotoxins (the septic form). This infection can lead to life-threatening hypovolemic shock and septic shock and requires intensive care including antibiotics. Nontyphoidal Salmonella serotypes are zoonotic and can be transferred from animals and between humans. They usually invade only the gastrointestinal tract and cause salmonellosis, the symptoms of which can be resolved without antibiotics. However, in sub-Saharan Africa, nontyphoidal Salmonella can be invasive and cause paratyphoid fever, which requires immediate antibiotic treatment.