TYPHUS FEVER, TRENCH FEVER, ETC. 945 



Immunity. A single attack of typKus fever seems to protect 

 permanently. Monkeys and guinea-pigs that have once passed 

 through the febrile reaction are thereafter refractory. 



Prophylactic vaccines made from various bacteria isolated from 

 typhus cases have not in our opinion given convincing proof of 

 success. Attempts to immunize prophylactically with inactivated 

 typhus blood have not so far had sufficient test. Specific therapy 

 with the serum of convalescents attempted by Nicolle and others 

 have not yet borne sufficient fruit to warrant very much hope. 



The Weil-Felix Reaction. This reaction is of peculiar interest 

 in that it represents a diagnostic serum reaction in typhus with an 

 organism which quite surely has no etiological relationship to the 

 disease. It was first described by Weil and Felix 28 in 1916, after 

 isolation, from the urine of a case of typhus fever> of an organism 

 which agglutinated in the serum of the patient in a dilution of 

 1 :200. The organism apparently belonged to the proteus type and 

 was designated by them as " Proteus X 2 . " Further study with it 

 showed that similar cases also agglutinated this organism. Later 

 another bacillus X 19 , very similar to the first one, was isolated from 

 another case. 



The organism is a Gram-negative, motile bacillus which ferments 

 glucose and lactose, coagulates milk with acid formation, liquefies 

 gelatin and in colony appearance resembles the proteus group. 

 Bengston 29 of the United States Public Health Service has studied 

 the two organisms ("X 2 " and "X 19 " of Weil and Felix) bac- 

 teriologically, and has compared them to laboratory cultures of 

 proteus. She found that they were very slow gelatin liquefiers, 

 that they were extremely slow in digesting coagulated blood serum, 

 but that they did not ferment lactose. In this, the organisms of 

 Weil and Felix which she studied resembled one reported by Fair- 

 ley. 30 Agglutination reactions, against proteus sera produced with 

 other strains, were in some cases active against these strains, and 

 conversely sera produced with the Weil-Felix strains were more active 

 against some other proteus organisms. 



Apparently the agglutination of proteus "X" strains is of dis- 

 tinct value in typhus diagnosis. Fairley observed positive agglutina- 

 tion of these organisms in 97 per cent of the typhus sera which 



28 Weil and Felix, Wien. klin. Woch., No. 2, 1916. 



29 Bengston, Jour. Infec. Dis., 24, 1919, 428. 



30 Fairley, Jour, of Hyg., 18, ]9]9, 203. 



