ABSTRACT
I. BACKGROUND Salmonella is a genus of the family Enterobacteriaceae (1). This genus is named in honor of D. E. Salmon, an American bacteriologist and veterinarian who studied animal-pathogenic salmonellae. These enteric (i.e., associated with the intestine) bacteria are gram-negative, usually motile, facultatively anaerobic, and non-spore-forming bacilli. Salmonella infections of humans and animals continue to be a major public health problem worldwide and also have a large negative economic impact on food production. Enteric fever (i.e., typhoid or paratyphoid fever) is a more serious form of salmonellosis in which specific salmonellae produce invasive disease in humans. The incidence of human typhoid fever in developing countries was recently estimated to be 17-20 million cases annually, with 600,000 deaths, most of which occur in Asia (2). However, the incidence and severity of enteric fever vary geographically, but disease is infrequent in developed nations. Variably high levels of endemic enteric fever exist in developing regions of the world, and imported human cases or contaminated food from endemic regions continue to cause problems in developed nations (3).
