860 



BACILLUS 



Pathogenicity. — May give rise to conjunctivitis, iridochoroiditis, and panophthalmitis in 

 man. Occasionally invades the blood stream in cachectic diseases. 1 ml. 24-hours' 

 broth culture sometimes proves fatal to mice injected intraperitoneally ; sub- 

 cutaneous inoculation into rats occasionally gives rise to a local infiltration, and 

 to submiliary abscesses in the lungs. Most strains are non-pathogenic. 



B. mesentericus and B. vulgatus 



Fliigge (1886) first described an organism, generally known as the potato 

 bacillus, under the name B. mesentericus vulgatus. There is a tendency now to 

 regard B. mesentericus and B. vulgatus as two distinct species, though Flynn and 

 Rettger (1934) think that they are variants of a single species. Even the most 

 recent descriptions, such as those of de Soriano (1935) and Lamanna (194:0c), 

 are not in entire harmony, and it is difficult in the absence of international agree- 

 ment to do more than reproduce the characters that have been assigned to these 

 organisms. 



A variety, by some regarded as a distinct species, of B. mesentericus is B. 

 mesentericus fuscus (Fliigge) or the brown potato bacillus. It resembles B. 

 mesentericus, but differs from it in being slightly smaller, in having less tendency 

 to thread formation, and in forming on agar and potato a thinner, greyish-brown 

 layer of growth. A red potato bacillus was described by Globig (1888) as B. 

 mesentericus ruber. It is sometimes known as B. globigii Migula. On potato it 

 forms a reddish wrinkled growth of a tough viscous consistency. There is also 

 a black potato bacillus, first described as B. mesentericus niger, and sometimes 

 known as B. aterrimus Lehman and Neumann ; on solid media, especially on 

 potato, it gives a characteristic thick, wrinkled, black growth. A bacillus, B. 

 mesentericus panis viscosi, sometimes known as B. panis, is responsible for ropy 

 bread. 



Bacillus vulgatus (Fliigge) Trevisan 

 Synonyms. — B. mesentericus vulgatus ; potato bacillus. 

 Habitat. — Found in dust, soil, water, milk. 

 Morphology. — Rather slender, about 2-4 /n x 0-75 /j, ; slightly rounded ends, occurring 



singly and in short chains. Motile by peritrichate flagella. Spores ovoid, 1-5 ^ 



X 0-6 fi, formed sub-terminally, do 



not , cause bulging of the cell, and 



germinate equatorially with splitting 



along the transverse axis. Non- 

 capsulated. Gram - positive. Non- ., - . 



acid-fast. 



Fig. 185. — B. vulgatus. 



Smooth type of colony. Agar, 24 hours, 



37° C. (X 8). 



Fig. 186." — B. vulgatus. 

 Same colony as in Fig. 185, after 48 hours' 

 incubation, showing marked irregularity 

 of surface and edge, and raised peri- 

 pheral ring ( X 8). 



