I. DEFINMION OF THE ARIZONA GROUP (17) confirmed all the above-mentioned observa-The Arizona group of the family Elterobac-tions with the exception that 33.2 per cent of teriaceae is composed of bacteria closely related 457 monophasic Arizona strains tested utilized to the members of the genus SalmoneUa but dis mucate within 20 hr, whereas none of 164 ditinguishable from them by biochemical methods. phasic strains did so. Twelve reaction patterns The biochemical properties of the two groups were obtained in testing 1136 salmonellae and are delineated in table 1. The reactions listed are 621 Arizona strains in the four organic acid those given by typical members of the two groups media. Six of these reaction patterns contained and exception may be taken to them on the 93.7 per cent of the salmonellae whereas three ground that the two reaction patterns are very other patterns contained 98.7 per cent of the simiar and that not every culture of the groups Arizona cultures. The results are summarized adheres to the patterns delineated. For instance, briefly in table 2. a number of well known Salmonela types fail At the time Edwards et al. (16) published an to ferment dulcitol and a few rare types liquefy extended study of Arizona serotypes, some diffigelatin. Nevertheless, the tests listed above are culty was encountered in framing a definition of those used in the laboratory for primay group the group. Subsequentiy the KCN test as modidifferentiation of Enterobacteriaemae and when fied by Moeller (29) and the lysine decarboxylase interpreted judiciously in combination with the tests of Moeller (30) and of Carlquist (6) have results of serologic examination, an excellent come into general use so that no difficulty now is indication can be obtained as to which of the two experienced in ditingug Arizona strains groups a given culture belongs. Gelatin liquefac-from those of Citrobacter (Eschrichia freundii) tion is a very constant property of the Arizona (Edwards and Fife (10); Edwards et al. (13)). group and the test can be made much more useful Certain biochemical characteristics of Arizona if the rapid method of Kohn as modified by Lau-strains are somewhat less uniform than those of trop (27) is used. SalmoneUa serotypes. In studying the ability of Certain additional tests are of value in differen-the two groups to grow in KCN medium, Edtiating the two groups. Schaub (34) noted that wards and Fife (10) found that whereas only 1.1 Arizona strains utilized malonate whereas sal-per cent of the Salmonella strains tested were monellae did not. This observation was confirmed positive, 7.7 per cent of the Arizona strains were by Shaw (37). Kauffmann and Petersen (25) able to initiate growth. It should be stated, hownoted that salmonellae utilized D-tartrate, mu-ever, that the majority of Arizona cultures which cate, and citrate rapidly, whereas Arizona culwere KCN positive belonged to 0 group 21 and tures did not. In the examination of a large series that strains of the 0 group were almost constantly of SalmoneUa and Arizona...

No abstract

The resistance of cultures of Salmonella typhimurium to tetracyclines and chloramphenicol has been examined periodically. Although none of 200 cultures isolated prior to 1948 was resistant to the antibiotics, 5 % of 100 cultures from man and 9 % of 100 cultures from fowls which were isolated in 1956 and 1957 were resistant to tetracyclines. Among 158 cultures isolated from man and 100 cultures isolated from fowls in 1959 and 1960, 13.9 and 29 %, respectively, were resistant to tetracyclines. In the last series, cultures resistant to chloramphenicol were found for the first time. Among 150 cultures of other Salmonella serotypes from man and 137 similar cultures isolated from fowls in 1959 and 1960, 5.3 and 8 %, respectively, were found resistant to tetracyclines. There is no obvious explanation for the higher percentage of resistant strains occurring in S. typhimurium than in other serotypes.

SUMMARYA new type of phase variation which changes in one direction only has been noted in some members of the Salmonella group, This was found in association with three hitherto undescribed flagellar antigens, z43, z46 and z~~, which are characterized.These occurred naturally with particular frequency in Salmonella group E and in cultures which possessed an alternate g, s, t phase. Two of these antigens, z43 and were found less frequently in other 0 groups and in organisms possessing other alternative phases. Although the antigens in question can be readily transformed to the alternate phases of the organisms in which they occur, these alternate phases could not be changed to zm, zas or z4s.

No abstract