LACTOBACILLUS BREVIS 761 



Oelatin /Stoft.— Grows to the bottom. No liquefaction. 



Oelatin Agar Shake. — Deep colonies are roughly biconvex or tam-o'-shanter-shaped. 



Broth. — Uniform turbidity ; sometimes the growth settles to the bottom. 



Resistance. — Not particularly resistant. Killed by 56° C. in 25 minutes, and by 2 per 

 cent, phenol in 1\ minutes. Highly resistant to acids ; will withstand incubation 

 for 24 hours at 37° C. in broth of pH 3-5. No growth above pH 9-1-9-6. 



Metabolism. — Aerobe and facultative anaerobe. 



Biochemical. — Sugar reactions variable. Usually produces acid in glucose, maltose, sahcin 

 and lactose, but not in sucrose, dextrin, dulcitol, or raffinose. L.M. acid and clot 

 in 2 to 3 days ; lower | of tube decolorized. Indole negative. Final pH in glucose 

 broth cultures is about pH 2-75. Chief acid formed is malic acid ; lactic acid is 

 formed in only a very small amount. Methyl-red positive. Voges-Proskauer 

 negative. Nitrates not reduced. Catalase very slight positive. NHj negative. 



Antigenic Structure. — Appears to be fairly homogeneous, and to be closely related to L. 

 odontolyticus II, and to L. acidophihis. 



Pathogenicity. — Suspected of being responsible for production of dental caries. Non- 

 pathogenic to laboratory animals. 



Lactobacillus odontolyticus II 



solation. — Isolated by Mcintosh, James, and Lazarus-Barlow in 1922 from carious teeth 

 and from saUva, and called B. acidophilus odontolyticus II. 



Morphology. — Rather short bacillus, 1-2 /^ long by 0-5 /i broad, usually arranged in short 

 chains. Often very pleomorphic, coccal forms being mixed with bacillary forms 

 in the same chain ; may closely resemble a streptococcus. Non-motile. Gram- 

 positive. 



Cultural Reactions.- — Similar to odontolyticus I. 



Resistance and Metabolism. — Similar to odontolyticus I. 



Biochemical. — Variable sugar reactions. 7 out of 18 strains produced acid in glucose, 

 lactose, and sucrose. L.M. Some strains produce acid and clot, others have no 

 action on it. Indole negative. 



Antigenic Structure. — Closely alhed to odontolyticus I and to L. acidophilus. 



Pathogenicity. — Like odontolyticus I. 



Lactobacillus brevis 



Synonyms. — Probably L. pentoaceticus ; B. acidophil-aerogenes. 



Isolation. — By Torrey and Rahe in 1915 from the faeces of human beings, sheep and hens. 



Habitat. — Common in fermenting plant and animal products. 



Morphology. — Variable morphology. Size given by some authors as 1-5-11 -5 n long by 

 0-8 jii broad, and by others as 1-4 fi long by 0-6-0-8 fi broad ; often arranged 

 in long, curved strings. Non-motile. Gram-iaositive. Stain uniformly with 

 Loeffler's methylene blue. 



Cultural Reactions. — On glucose oleate agar it forms either (1) small, round or navicular, 

 opaque, whitish colonies surrounded by an areola of turbid agar : or (2) tiny, 

 round, translucent, greyish colonies with a finely erose edge ; on microscopic 

 examination these appear typically rhizoid. In glucose broth a growth forms 

 adherent to the bottom and sides of the tube ; on shaking this gives rise to a dense 

 turbidity. 



Resistance. — Highly resistant to acids ; will remain alive in a glucose broth culture at 

 37° C. for 1 week. 



Metabolism. — Microaerophilic. Range of growth 10°-45° C. ; optimum temperature 

 30°-35 °C. 



