CHAPTER 34 



BRUCELLA 



Definition.— 5?-((ceZ/a. 



Small, non-motile, non-sporing, Gram-negative cocco-bacilli. Grow rather 

 poorly on ordinary media, or may require special media. Aerobic ; no growth 

 under strict anaerobic conditions. Growth often improved by COj. Little or no 

 fermentative action on carbohydrates. Usually tend to produce alkaU in litmus 

 milk, and a brown pigmentation on potato. Strict parasites, occurring in man 

 and animals, and producing characteristic uifections. 



Type species. Brucella melitensis. 



History. — The first member of the group, Br. melitensis, was isolated in 1887 

 by Bruce from the spleen of patients who had died of Malta fever. At that time, 

 and for a long time afterwards, the bacillary nature of the organism was not 

 recognized ; in all the older textbooks it is therefore described as a micrococcus. 

 The organism finds its natural habitat in the goat and the sheep. It may, however, 

 infect other animals. In man it gives rise to undulant fever. It is fairly widely 

 distributed throughout the world. 



The discovery of the second member, Br. abortus, was made by Bang of Copen- 

 hagen in 1897. Working in conjunction with Stribolt, he isolated the organism 

 from cows suffering from infectious abortion, and by a series of experiments demon- 

 strated its specific role in this disease. The organism is parasitic in cattle. To a 

 less extent it infects certain other animals. In man it gives rise to undulant fever. 

 It is perhaps even more widespread than Br. melitensis, having been found in practi- 

 cally every country of the world. 



The third member of the group, Brucella tularensis, was isolated by McCoy 

 and Chapin in 1912 from a plague-like disease among rodents in California, and was 

 called by them Bacterium tularense. It infects ground-squirrels, jack-rabbits, and 

 other rodents, and occasionally gives rise to a disease in man called tularaemia. 



The fourth member, Br. suis, was isolated by Traum (1914) from the foetus of a sow. 

 It is a natural parasite of pigs, in which it gives rise to a disease frequently character- 

 ized by inflammatory lesions in the reproductive organs. It may occasionally infect 

 other animals. In man it shares with Br. melitensis and Br. abortus the ability 

 to produce undulant fever. It appears to be very much less widespread than these 

 two organisms, its chief home being in the large hog-raising districts of the middle 

 western states of North America. In Denmark, Br. suis strains have been isolated 

 by Thomsen (1931, 1934), which differ in certain respects from those found in the 

 United States ; they will be referred to as the Danish porcine type. The American 

 type has been found occasionally in Europe (see Thomsen 1934), and has been 

 reported from Brazil (Neiva, 1934), the Argentine, and Australia (King 1934), 



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