THE DISEASE CAUSED BY SALMONELLA DISEASES and flagellar (H) antigens of the organism. Sub-division of certain species, especially S. typhosa and S. Typhimurium, can be achieved by bacteriophage typing. Specific identification of all isolates is desirable, especially for epidemiologic reasons, and can be obtained through local, state or federal health agencies.
Salmonella species most frequently isolated from human infections in the United States during 1968 are, in descending order of frequency, S. Typhimurium, S. enteritidis, S. Heidelberg, S. Newport, S. saint-paul, S. infantis, S. Thompson, S. typhosa, S. Havana, and S. Blockley. These ten serotypes accounted for about 72 percent of the total salmonellae isolates from a man during 1968. S. Typhimurium is the serotype most frequently isolated year after year, usually accounting for 20 to 30 percent of the total.
The genus Salmonella consists of more than 1300 serologic types. The majority of serotypes are capable of producing disease in animals and man and should be considered as primary pathogens of animals that are readily transmitted to man. A few serotypes, among which Salmonella typhosa is the best example, exhibit marked host preference. S. typhosa is a parasite of man only and does not cause disease in lower animals in nature.
THE DISEASE CAUSED BY SALMONELLA Human infection with salmonellae may be expressed as acute gastroenteritis (“food poisoning”), enteric fever (typhoid or paratyphoid fever), or bacteremia with or without clinical evidence of localized infection. Asymptomatic transient infection of the intestinal tract is also com-mon with certain species. A chronic carrier state may occur after infection with S. typhosa or occasionally other serologic types, and is characterized by prolonged excretion of salmonellae in feces or urine. Typhoid fever is considered separately here because of its historical identity, the host specificity of the pathogen, and the wealth of data on basic and clinical aspects of the disease.’
This approach is unrealistic to the extent that an illness closely resembling typhoid fever can result from infection with other salmonellae, and S. typhosa can on occasion produce all of the clinical syndromes described for the other salmonella serotypes. Etiology. Salmonellae are gram-negative, aerobic, nonsporting rods that are motile (with the exceptions of S. pullorum and S. gallinarum) and that grow readily on simple culture media. Presumptive identification of salmonellae involves relatively simple biochemical and agglutination reactions, but definitive identification of species depends on a precise analysis of the somatic.