THE VARIABILITY OF CERTAIN STRAINS OF DYSENTERY 

 BACILLI AS STUDIED BY THE SINGLE-CELL METHOD 



By Marshall A. Barber 



(From the Biological Laboratory, Bureau of Science, Manila, P. I.) 



One plate and 1 text figure 



During the summer of 1912, a considerable number of stools 

 from cases of bacillary dysentery occurring in Manila came 

 into the laboratory. Some of the cultures from these stools 

 showed a tendency to variability, and it was decided to study 

 some of these variations by the single-cell method. 



This method, described by me in previous publications,^ en- 

 ables the worker not only to obtain easily pure cultures arising 

 from a single cell, but also to select any aberrant cell lying 

 among myriads of normal ones and to substitute the single-cell 

 cultivation for plate cultures in obtaining a series of selections. 

 Further, one may more easily avoid the contaminations which 

 are especially liable to occur in the Philippine Islands when 

 plate cultures are used. A description of the technique is given 

 below. The difficulties of using the method are not great. Pure 

 cultures may be made at the rate of 50 per hour under favorable 

 circumstances. 



Two types of variations were studied; one characterized by 

 fermentative, the other by morphological, characteristics. 



I. FERMENTATIVE CHANGES WITH RESPECT TO MALTOSE 



A culture, laboratory strain 105200, furnished by Dr. Otto 

 Schobl of this Bureau, was isolated July 7, 1912, from a typical 

 bloody stool of a case of bacillary dysentery. This strain was 

 mannite fermenting, and otherwise showed the characteristics 

 of dysentery bacilli of the Flexner type. A pure culture was 

 made by the isolation of a single bacillus, and this culture was 

 grown on ordinary agar for about eighteen days. Transfers were 

 made on September 12, 1912, to ordinary broth, and allowed to 

 grow from two to five hours, in order to obtain actively growing 



'Set. Bull, Kansas Univ. (1907), 4, 3; Journ. Infect. Dis. (1908), 5, 380; 

 (1909), 6, 634. 



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