Application of Molecular Methods to the Study of Infections Caused by Salmonella spp.

Disease caused by any member of the genus Salmonella is termed salmonellosis. The type of disease and its symptoms are generally related to the mfecting species and reflect the invasiveness and virulence of the organism. For example, enteric fevers are systemic diseases usually resulting from infection with Salmonella typhi, S paratyphi A, B, or C. Salmonellosis is caused by more than 2200 different salmonella serotypes, which can be classified into three groups according to their adaptation to human and animal hosts. One group of serotypes can be regarded as those as organisms that cause enteric fever only in humans and higher primates. Members of this group, which includes S. typhi, S paratyphi A, B, and C are restricted to humans and higher primates and are not found in food animals. A second group causes diseases in specific animals (e.g., S. dublin —cattle, S. pullorum —-poultry, S choleraesuis —pigs). However, when some members of this group cause infections in humans the disease is frequently invasive and can be life-threatening (e.g., S. cholerae-suls, S dublin ). The third group, which includes the great majority of the remaining 2000+ serotypes, typically causes mild-to-moderate enteritis in humans, which is often self-limiting, but which can be severe in the young, the elderly, and in patients with other underlying complications This group includes the four serotypes most common in humans in England and Wales at the present time: S. enteritidis, S, typhimurium, S. virchow, and S. hadar . The great majority of serotypes of this third group are zoonotic in origin and have as their reservoirs animals used for food, particularly cattle, poultry, and pigs.