A series of nine cases of paratyphoid fever due to infection with anaerogenic strains of B. paratyphosus B are recorded.Biological examination of these strains shows no difference from the ordinary type of B. paratyphosus B except the inability to produce gas from any “sugar.”Serologically these strains are identical with the aerogenic type of the organism.These anaerogenic strains retain their inability to produce gas from “sugar” after subculture on artificial media for a considerable period, and cultivation on a number of different fluid media failed to restore the gas producing power.In the organic salt fermentation test B. paratyphosus B gives a characteristic reaction which is also given by the anaerogenic strains.The fermentative varieties of B. paratyphosus B defined by Kristensen and Bojlèn are definite and can be identified as a matter of practical routine, but the test is delicate and requires care in the preparation of the media and especially in the Bitter test.The existence of these apparently stable fermentative varieties of B. paratyphosus B is likely to be of use in epidemiological investigations.We wish to thank a number of people whose assistance has made it possible for us to carry out this work. Dr J. A. Charles, Medical Officer of Health, Newcastle-on-Tyne, for permission to publish these cases; Dr E. F. Dawson-Walker, Assistant M.O.H., for histories and specimens from the cases. Dr W. M. Scott for many cultures and other assistance.Dr M. Kristensen, Copenhagen, Dr M. A. C. Buckell, Bradford, Dr P. L. Sutherland, Wakefield, for paratyphoid cultures and Dr J. W. H. Morrison, M.O.H., Blaydon-on-Tyne, for a number of specimens.

No abstract

No abstract

1. Anaerogenic races ofB. paratyphosusB are stable in ordinary artificial culture.2. Aerogenic variants of anaerogenic strains can be produced (though the anaerogenic strain persists) by growth in dextrose or mannitol with a relatively large amount of sodium formate. Such variants can then produce gas from all the other “sugars” fermentable byB. paratyphosusB.3. Failure to produce gas from sugars by anaerogenic races is due to deficiency in the power of breaking down the formate produced in the first stage of fermentation.4. A mixture of dextrose and formate in peptone water reveals the latent capacity for gas production in anaerogenic races ofB. paratyphosusB. This confirms the observations of Grey (1914, 1920, 1924).Since this work was done, we have seen the paper of Pot and Tasman (1932) in which they succeed in isolating aerogenic variants from anaerogenic cultures ofB. paratyphosusB by continued cultivation in 2 per cent. calcium formate, in a somewhat similar manner as we have done with the mixture of dextrose and sodium formate.