Caries-producing organisms were isolated in glucose-broth at pH 3.5, although this was not the best medium in which to grow them. Malic acid was the chief acid present ; lactic acid occurred only in traces. The isolated organisms—two closely related characteristic types of B. acidophilus—were named B. acidophilus odontolyticus: Types I and II. One or other of these types is present in all carious teeth. Artificial caries, histologically the same as that occurring in ” normal ” caries, was produced in human teeth with pure cultures of these organisms. Attempts to produce artificial caries in the teeth of animals were unsuccessful.
The degree of alkalinity of saliva in rabbits appeared to be protective against caries. Saliva mixed with a broth culture of B. acidophilus odontolyticus showed no greater bactericidal action than control culture. Teeth were kept for eighty-fourweeks in broths ranging in pH from 5 to 1. Decalcification did not occur noticeably in media having less acidity than pH 4. Decalcified teeth were readily acted upon by proteolytic organisms after the acid had been neutralized or diluted.
References: (with James McIntosh and L. Barlow) Brit. J. Exp. Path., 1922, 1924, 1925.