454 PATHOGENIC MICROORGANISMS 



The pathogenicity of Bacillus lactis aerogenes for man is slight. 

 Its chief claims to importance lie in its milk-coagulating properties 

 and its almost constant presence in the human intestine. In infants, it 

 may give rise to flatulence and it has been occasionally observed as the 

 sole incitant of cystitis. Among such cases rare instances have been 

 observed in which it has formed gas in the bladder (pneumaturia). 

 When this occurs the urine is not ammoniacal but remains acid. 



Different strains of this bacillus vary much in their pathogenicity 

 for animals. Wilde claims that it is more pathogenic for white mice and 

 gionea-pigs than is the bacillus of Friedlander. He speaks of it as the 

 most virulent member of this group. Kraus, writing in Fluegge's 

 "Mikroorganismen," rates its pathogenicity less high. 



Closely related to this bacillus, as well as to those of the Friedlander 

 group, is an encapsulated bacillus isolated from a case of broncho- 

 pneumonia by Mallory and Wright, 1 which is strongly pathogenic for 

 mice, guinea-pigs, and rabbits'. 



BACILLI OF THE PROTEUS GROUP 



The bacilli of this group have little pathological interest, but are im- 

 portant because of the frequency with which they are encountered in 

 routine bacteriological work. They may confuse the inexperienced 

 because of a superficial similarity to bacilli of the colon-typhoid group. 

 In form they may be short and plump or long and slender, staining easily 

 with anilin dyes and decolorizing with Gram's method. They are ac- 

 tively motile and possess many flagella. Individuals stain irregularly, 

 often showing unstained areas near the center. The so-called Bacillus 

 proteus vulgaris described by Hauser 2 in 1885 is the type of the group. 



Bacilli of this group are widely distributed, being found in water, 

 soil, air, and wherever putrefaction takes place. In fact, proteus is one 

 of the true putrefactive bacteria possessing the power to cause the cleav- 

 age of proteids into their simplest radicles. 



Bacillus proteus vulgaris grows best at temperatures at or about 

 25 C. and develops upon the simplest media. It is a facultative anae- 

 robe and forms no spores. In broth^t produces rapid clouding with a 

 pellicle and the formation of a mucoid sediment. In gelatin, the colonies 

 are characteristically irregular, giving the name to this group. 



Gelatin is rapidly liquefied. Liquefaction, however, is diminished 

 or even inhibited under anaerobic conditions. 



1 Mallory and Wright, Zeit. f. Hyg., xx, 1895. 



2 Hauser, "Ueber Faulniss-Bakt.," Leipzig, 1885. 



