BRUCELLA TULARENSIS 833 



Brucella suis 



Isolation. — American type by Trauiii (1914) from the foetus of a sow, and Danish type by 

 Thomsen (1931). 



Habitat. — Strict parasite, occurring in pigs and man. 



Morphology. — Similar to Br. abortus. 



Cultural Characters. — Similar to those of type species, except that growth is never improved 

 by addition of COj. In shake agar cultures growth occurs on the surface. No 

 growth under strictly anaerobic conditions. The American tyjie grows rather more 

 freely than the Danish type. On liver agar plates both types grow in the presence 

 of thionin, but are inhibited by basic fuchsin, methyl violet, and pyronin. The 

 Danish type has the same differential susceptibiUty as the American type, but is 

 rather more susceptible to all dyes ; consequently half the usual concentrations of 

 dye should be employed when testing it. 



Resistance. — Similar to that of type species and Br. abortus. 



Metabolism. — Similar to type species, but growth is not improved by COj. Brown colora- 

 tion in old agar cultures less common than with Br. melitensis. 



Biochemical. — Similar to tj^e species, but American tj'pe produces HjS in liver agar for 

 at least 4 days ; Danish type produces no HgS. 



Antigenic Structure. — Appears to possess the same antigens as Br. melitensis, but dis- 

 tributed in quantitative proportions nearer those of Br. abortus than Br. melitensis. 

 Provided absolutely smooth strains are used, it may be differentiated from Br. 

 melitensis, but not from Br. abortus, by quantitative absorption of agglutinins. 

 The rough variant, incorrectly referred to as Br. parasuis, is agglutinable by non- 

 specific agents. 



Palhogenicity. — Gives rise to a disease of pigs, which may be accompanied by abortion, 

 and to undulant fever in man. May infect cows and be excreted in the milk. 

 Experimentally, it is pathogenic to a variable degree for man, pigs, cows, 

 monkeys, and the small laboratory animals. Possibly pathogenic to some 

 degree for horses and dogs. The rough variant is avirulent. 



Brucella tularensis 



This organism is a tiny, non-motile. Gram-negative bacillus, which was isolated 

 by McCoy and Chapin in 1912 from rodents suflfering from tularaemia (see Chapter 

 75). In the animal body, it occurs as a coccoid or rod-shaped organism 

 surrounded by a clear area, which probably represents a capsule. The diameter 

 of the organism is 0-3-0-7 fi long by 0-2 n wide ; the diameter with the capsule is 

 0-4-1 -0 /x by 0-3-0-5 //. The organisms stain best with carbol-fuchsin or aniline 

 gentian violet ; with methylene blue they stain very poorly and show no capsule. 

 In culture, coccoid forms alone are seen (Wherry and Lamb 1914) ; a capsule is 

 visible if the organisms are mixed with serum. No growth occurs in the usual 

 media. It was first cultivated on Dorset's egg, but later it was found that coagulated 

 egg yolk was more satisfactory (McCoy 1912). On this medium the maximum 

 growth is reached in 2 days ; it is pale, translucent, slightly mucoid, and pearly 

 in appearance, not easily distinguishable from the medium ; it is readily emulsi- 

 fiable. Growth occurs also on glucose blood agar, glucose serum agar, and blood 

 agar slopes, provided that a piece of rabbit's spleen is rubbed over the surface and 

 then left in the condensation water (Francis and Lake 1922) ; and on agar to 

 which 0-02 per cent, of cystine is added (Francis 1922, 1923). On these media the 

 organism should be subcultured every other day, but on egg yolk it may remain 

 viable for 3 months (Wherry and Lamb 1914). Shaw and Hunnicutt (1930) 

 recommend a medium composed of brain veal infusion agar, pH 7-6, containing 5 

 per cent, rabbit serum, 1 per cent, dextrose, and 005 per cent, cystine, while Kudo 

 P.B. EE 



