PARATYPHOID BACILLI 379 



enteric type constitute the commonest paratyphoid infections of 

 man, and originate, as in the case of true typhoid, through the 

 bacilli gaining entrance by the mouth. The intestinal lesions 

 are the most manifest effects of the organisms, which occur 

 in large numbers in the stools ; their presence in the blood also, 

 especially in B infections, is a marked feature — even more so 

 than in typhoid fever, and they have also been isolated from the 

 skin eruptions. They persist in the intestine during con- 

 valescence, and paratyphoid carriers have been recorded. Para- 

 typhoid infections are found all over the world ; in India and 

 Sumatra cases of paratyphoid A infections with relatively few 

 intestinal symptoms have been recorded as of relatively frequent 

 occurrence. The illness here lasts from nine to fourteen days 

 and is characterised by headache, pains in the neck and loins, 

 fever, occasionally by diarrhoea, bronchitis, and a rash (sometimes 

 morbilliform),' and usually it is non-fatal. Gall-bladder infec- 

 tions with b. paratyphoid A are common. 



In animals the paratyphoid bacilli have pathogenic effects 

 similar to those of the b. typhosus — septicsemic and pytemic 

 manifestations rather than intestinal conditions being originated. 



As in typhoid fever patients suffering from paratyphoid 

 develop specific agglutination phenomena in their blood serum 

 through the organism (be it A or B) with which they are infected. 

 This is not only of importance in relation to diagnosis but is 

 also evidence of the causal relationship of the organism to the 

 disease. With paratyphoid B when a patient's serum in . a 

 dilution of 1 in 25 agglutinates the organism a positive diagnosis 

 may be made ; with paratyphoid A the amount of agglutinins 

 formed may be less and here many experienced observers give a 

 positive diagnosis when agglutination is obtained with a serum 

 diluted 1 in 10. In using such data for diagnostic purposes the 

 previous preventive inoculation of the patient witli paratyphoid 

 bacilli must be excluded. 



Further points regarding the agglutination of these organisms 

 (p. 390) and the methods of isolation (p. 388) will be treated 

 later. 



Preventive Inoculation. — All the evidence points to inoculation 

 with the b. typhosus having no effect in protecting against para- 

 typhoid fever. It is therefore now customary, when exposure to 

 both infections is anticipated, to use for the inoculation a mixture 

 containing in the dose 500 million b. typhosus, 250 million 

 b. paratyphosus A, and 250 million b. paratyphosus B — two 

 doses (the second being double the first) being given at the 

 same interval as with the original typhoid vaccine. 



