INTESTINAL OR COLON-TYPHOID GROUP 275 



organisms, rather than to the typhoid-dysentery group. Similar 

 organisms have been isolated repeatedly since that time in some 

 instances from typical typhoid cases, in others from cases that had 

 all the clinical symptoms of typhoid, but that did not give the 

 agglutination reaction. 



Morphology and Staining. This organism corresponds closely 

 in morphologic and staining characters to the Bacillus enteritidis 

 and the Bacillus cholera suis. 



Isolation and Culture. The organism has been isolated in 

 pure culture directly, from the blood, and by plate cultures 

 from the internal organs in disease, and particularly from the 

 intestinal contents of man and of the lower animals. In gen- 

 eral cultural characters the organism resembles the B. enteri- 

 tidis. It has been found in practice that two varieties may be 

 differentiated, termed A and B, respectively. Type A does not 

 produce a terminal alkalinity in milk and dissolve the casein, 

 and in that respect differs from B. enteritidis, while type B corre- 

 sponds exactly. 



Physiology. Not markedly different from B. cholera suis. 



Pathogenesis. Paratyphoid fever in man has been attended 

 by a low mortality; in consequence few autopsies have been re- 

 ported. In both animals and man infection partakes more of the 

 nature of an acute enteritis than does typhoid fever; the lymph- 

 atics are not generally invaded as in typhoid, and the Peyer's 

 patches are not swollen and ulcerated. 



Immunity. Probably an endotoxin, less soluble, but in some 

 respects similar to that of B. enteritidis, is produced by these 

 organisms. Agglutinins are produced in infected individuals. 

 The agglutination reactions of types A and B differ markedly. 

 It was this difference which first suggested the existence of the two 

 types. No method of practical immunization against the disease 

 is known. 



Bacteriologic Diagnosis. The differentiation of paratyphoid 

 may be made clinically by the specific agglutination tests. The 

 absence of a test in a case of clinical typhoid calls for a repetition 

 with the two types of paratyphoid bacilli. 



Transmission. It is probable that certain gastro-intestinal 

 infections in cattle may be caused by organisms of this type, and 



