NON-SPECIFIC COMPONENTS IN S. PARATYPHI A 469 



All the cultures possessed the biochemical and serological prop- 

 erties generally attributed to S. paratyphi A with the following 

 exceptions: The strain Durazzo lacked antigen I of the Kauff- 

 mann-White classification and produced large amounts of hydro- 

 gen sulphide. In these respects it conformed to the description 

 of Kauffmann (1937). The remainder of the strains produced 

 smaller amounts of hydrogen sulphide, as evidenced by the black- 

 ening of lead acetate papers suspended over cultures in 2 per cent 

 Bacto-peptone water. In this connection it should be stated that 

 the observations of the writers confirm the conclusions of Hunter 

 and Crecelius (1938) that differences observed in hydrogen sul- 

 phide production by different members of the genus Salmonella 

 are quantitative and not qualitative. It is probable that all 

 Salmonella strains produce hydrogen sulphide and that the results 

 obtained in testing for its production depend upon the methods 

 employed for the detection of the substance. 



The methods employed to induce variation were largely the 

 same as those used by Edwards and Bruner (1939a) in the study 

 of S. abortus-equi. The organisms were grown in semi-solid agar 

 to which was added sufficient agglutinating serum to immobilize 

 the bacilli. The medium was inoculated by stabbing at one side 

 of the tube. Outgrowths from the line of stab occurred only 

 when the flagellar antigens were altered. The spreading growth 

 was transferred successively in tubes of the same medium until 

 the serological reactions indicated that the induced phase was 

 pure. The culture was then plated and isolations made from 

 single colonies for further study. Serum derived from phase 1 

 of the Bispebjerg type was used to induce variations in the normal 

 phase of the cultures. As additional phases were isolated agglu- 

 tinating serums were prepared from them. These were used in 

 the study of induced phases and in forcing the bacilli to produce 

 further alterations in the flagellar antigens. Serum derived from 

 > S. cholerae-suis var. kunzendorf was used in the reversion of non- 

 specific phases. In many instances, it was found necessary to 

 use combinations of serums to force variation in the desired direc- 

 tion or to revert induced phases to the original phase. When the 

 serums contained or H agglutinins which might interfere with 



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