Molecular epidemiological techniques for Salmonella strain discrimination.

Salmonellae are ubiquitous throughout nature where they infect or colonize humans, animals and even insects worldwide. The genus is comprised of a number of different antigenically distinct members, many of which have a particular niche within nature. Infection in animals and humans can be endemic or epidemic. Many nations have established extensive surveillance systems to track Salmonella infections and disrupt epidemic spread. Most of these surveillance projects rely on traditional serotype and phage type analyses to identify trends and potential outbreaks. Many clinical outbreaks cluster among a few serotypes so further discrimination is often needed. Molecular epidemiological techniques have been used to enhance surveillance and discriminate outbreak strains within these common serotypes. The institution of these techniques has led to enhanced detection of outbreaks worldwide. Molecular techniques used for Salmonella surveillance are described and comparisons of different molecular techniques are outlined. Overall, traditional serotype surveillance in association with one or several molecular typing techniques, especially chromosomal restriction fragment analysis with pulsed-field gel electrophoresis, appears to provide the most reproducible and comparable discrimination of epidemiologically-linked isolates at this time.