268 



p. 11. KEYES AND II. V. JORDAN 



et ah, 1960). In his studies to date, Fitzgerald ( 1962) has not found 

 caries in rats monoinfected with rat strains of Lactobacillus fermenti, 

 Lactobacillus acidophilus. Streptococcus lactis, and Streptococcus 

 fecalis var. zijmogenes. 



It was previously demonstrated that after the cariogenic flora of 

 animals had been depressed with an antibiotic, their caries experi- 

 ence was markedly less than in nondepressed controls or in reinfected 

 littermates (Keyes, 1960^; Keyes and Fitzgerald, 1963). See Fig. 4. 



INFECTED FEMALES 



ANTIBIOTIC 

 (PENICILLIN) 

 DEPRESSES FLORA 



NON-INFECTED 



SAME CAGE 



BOTH CARIOUS 



CARIOGENIC 

 S TREPTOCOCCI 



LABELLED" STRAINS 

 STREPTOCOCCI 



PLAQUE 



c "LABELLED" 



STREPTOCOCCI 



SAME CAGE 



•LABELLED" 

 CARIES 



TRANSMISSION OF 

 CARIOGENIC FLORA 

 TO OFFSPRING 



?9 



CARIOUS 



CARIES 



c/? 



"LABELLED" 

 (/9 CARIES 



o- ? 



"LABELLED" 

 CARIES 



o- ? 



CARIOUS 



o" 9 



'LABELLED" 

 CARIES 



CARIOUS 



Fig. 4. In the schematic diagram above, on the left are represented several 

 generations of hamsters which were caries-inactive as a result of depression of 

 the cariogenic microbiota. The infection has been reintroduced by contact with 

 infected animals, by an inoculation of both original sti-ains of streptococci and 

 "labeled" streptomycin-resistant strains, and also by the transfer of cariogenic 

 plaque. Following reintroduction of the cariogenic microbiota, caries is again 

 transmitted by natural passage as indicated by solid lines on the right. 



