CHAPTER XXVI. 1 



BACILLUS PARATYPHOSUS A. 



Introduction. 



Section I. Experimental inoculation, p. 424. 



Section II. Morphology, p. 424. 



1. Microscopical appearance and staining reactions, p. 424. 2. Cultural character- 

 istics, p. 424. 



Section III. Biological properties, p. 424. 



1. Biochemical reactions, p. 424. 2. Virulence, p. 425. 3. Toxin, p. 425. 4 Vac- 

 cination, p. 425. 5. Agglutination, p. 426. 6. Absorption tests, p. 427. 7. Com- 

 plement fixation, p. 428. 



Section IV. The diagnosis of paratyphoid A infections. The isolation and identification 

 of the bacillus, p. 428. 



The pseudo-paratyphoid A bacillus, p. 430. 



THE paratyphoid A bacillus was first described by Schottmiiller who 

 isolated it from the blood of patients suffering from a disease clinically 

 indistinguishable from enteric fever. 



Paratyphoid A fever is a septicaemia characterized by " a mild pyrexia simulating 

 enteric fever, marked by no acute gastric or intestinal symptoms and rarely fatal " 

 (Firth). The lymphatic system is less affected than in enteric fever though one 

 case is recorded where a single perforation was found (Grattan and Wood). 



The bacillus has never been isolated in England (Bainbridge) 2 and com- 

 paratively few cases of paratyphoid A infection have been recorded on the 

 Continent of Europe. In America its distribution is uncertain : but it is 

 worth noting that in one year in the Allegheny General Hospital the relation 

 of paratyphoid A fever (48 cases) to enteric fever was 8 to 11 (Proescher and 

 Roddy). 



In India, on the other hand, paratyphoid A fever is very prevalent. 

 Grattan and Wood estimate that one-third of the cases of " simple continued 

 fever " in India are cases of paratyphoid A fever, and so constantly is the 

 A variety of the bacillus found that paratyphoid fever in that country connotes 

 an infection with the paratyphoid A bacillus (Firth). 



The bacillus apparently remains in the system for a time after an attack of para- 

 typhoid A fever and " carriers " would appear to be the chief agent in the dissemina- 

 tion of the disease (Firth). Convalescents are usually infective for a comparatively 

 short period, and " chronic carriers " (persons in whom the bacillus remains more 

 than 3 months), would seem to be uncommon. 



1 This chapter has been rewritten. 



2 Bainbridge, F. A., The Milroy Lectures, Royal College of Physicians, Lancet, 1912, i. 



