SALMONELLA

 There are only two species of Salmonella, Salmonella bongori and Salmonella enterica, of which there are around six subspecies and innumerable serovars. The genus Escherichia, which includes the species E.coli belongs to the same family.

Salmonellae are found worldwide in both cold-blooded and warm-blooded animals, and in the environment. They cause illnesses such as typhoid fever, paratyphoid fever, and food poisoning.

Detection, culture and growth conditions

Most subspecies of Salmonella produce hydrogen sulfide,which can readily be detected by growing them on media containing ferrous sulfate, such as is used in the triple sugar iron test TSI.Most isolates exist in two phases: a motile phase I and a nonmotile phase II. Cultures that are nonmotile upon primary culture may be switched to the motile phase using a Cragie tube.

Salmonella can also be detected and subtyped using PCR rom extracted salmonella DNA, various methods are available to extract salmonella DNA from target samples.

Mathematical models of salmonella growth kinetics have been developed for chicken, pork, tomatoes, and melons.Salmonella reproduce asexually with a cell division rate of 20 to 40 minutes under optimal conditions.