FAMILY IV. ENTEROBACTERIACEAE 369 



Rods which are usually motile by means of peritrichous flagella, although non-motile 

 forms may occur. Gram-negative. Gelatin not liquefied. Indole not produced. Hydrogen 

 sulfide production is variable. Acid is produced from glucose, mannitol, maltose and sorbi- 

 tol. Gas production is usually observed (exceptions are Salmonella typhosa and Salmonella 

 gallinarum, but gas production maj^ also be absent in other species or serotypes). Lactose, 

 sucrose, salicin and adonitol are not attacked. The fermentation of other carbohydrates is 

 variable. Acetylmethylcarbinol is not produced. Methyl red test is positive. Nitrites are 

 produced from nitrates. Ammonium citrate is usually utilized. Urea not hydrolyzed. KCN- 

 sensitivity is negative (Moller, VI Internat. Cong. Microbiol., Rome, ;?, 1953, 316). All 

 known forms are pathogenic for man and/or other animals. 



The type species is Salmonella choleraesids (Smith) Weldin. 



Any organism showing the above-mentioned characters should be verified as a member 

 of the genus Salmonella by antigenic analysis. For most practical purposes the use of poly- 

 valent or group antisera will suflJice. Exact antigenic characterization and bacteriophage 

 typing for epidemiological purposes is the task oi Salmonella centers. Although manj^ strains 

 of Salmonella are at.ypical, these may be looked upon as exceptions which do not invalidate 

 the definition of the genus. 



Attempts to subdivide the genus Salmonella into valid species from the taxonomic point 

 of view have met with great difficulties. The Kauffman-White Schema (1955) (Edwards and 

 Ewing, Identification of Enterohacteriaceae, Burgess Publishing Co., Minneapolis, 1955, 

 52-60) lists 343 names. It is generally agreed that the vast majority of the organisms named 

 do not deserve species rank but should be considered as serological types. This fact has 

 been officially recognized by the Enterohacteriaceae Subcommittee in the addendum to the 

 report presented at the 6th International Congress for Microbiology, September 8, 1953, in 

 Rome. "It is the recommendation of the Subcommittee that from the date of publication 

 of this report all new serological types of Salmonella should be described by formula only 

 and not by name." The adoption of this proposal would lead to the undesirable situation 

 that 343 or more Salmonella types would be given names similar to those given to species, if 

 not by meaning, certainly by implication, and that others would be known by antigenic 

 formula only. The suggestion by Kauffmann and Edwards (Internat. Bull, of Bact. Nomen. 

 and Taxon., 2, 1952, 5) to divide the genus into three species, namely, Salmonella cholerae- 

 sids as type species. Salmonella typhosa on the basis of well recognized differences from 

 other members and Salmonella enterica to serve as species for all serological types, appears 

 too narrow and also somewhat contradictory as it practically means that two type species 

 are chosen. 



Recent observations by various workers on the transduction of antigenic characters raises 

 the question whether such changes also occur under natural conditions and should be taken 

 into consideration in epidemiological conclusions. It is as yet uncertain whether these 

 changes are permanent or whether reversion to the original characters occurs. Until more 

 exact knowledge on these factors is available, the possibility must be appreciated and 

 taken into account in epidemiological tracings. 



It is hardly possible to propose a classification for the salmonellas which can include all 

 the factors established for the large number of types. However, the genus is composed of 

 disease-producing organisms, and the first and foremost duty of any classification scheme 

 is to make it workable under practical routine conditions. "Systems of nomenclature are 

 for man's convenience and cannot hope to be wholly logical as to represent faithfully the 

 evolution of all living things" (Andrewes, Acta Path, et Microb. Scand., 28, 1951, 211). 

 From this point of view it seems justified to accord species rank to those organisms which 

 are easily identified because they are commonly encountered and/or cause rather well es- 

 tablished syndromes. 



Key to the species of genus Salmonella. 



I. Affect both man and other animals. 



A. Occur singly but not in pairs or chains. 



