6 MAX LEVINE 



smeared onto eosin-methylene blue agar for differentiation. One 

 organism was regarded as probably B. aerogenes and on confirmation 

 proved to be B. coli. Of 35 organisms recorded as B. aerogenes 34 

 (97%) gave the Voges-Proskauer reaction. Forty-nine organisms 

 were tentatively designated as B. coli or probably B. coli and all 

 proved to be negative for the Voges-Proskauer reaction. 



With organisms isolated from this group then, 34 out of 36 

 cultures regarded as B. aerogenes were confirmed as such while every 

 one of 49 strains regarded as B. coli was correct. 



CULTURES OBTAINED FROM EOSIN-METHYLENE BLUE AGAR AFTER 

 PRELIMINARY ENRICHMENT IN LACTOSE BROTH 



Fifty-two cultures were fished, 26 of which were regarded as 

 B. aerogenes and the remaining as B. coli. Of the 26 supposedly 

 B. aerogenes strains all gave the Voges-Proskauer reaction. Two of 

 the strains regarded as B. coli also gave the Voges-Proskauer reaction. 

 Thus 100% of the B. aerogenes strains and 92.4% of the B. coli 

 strains were correctly differentiated on eosin-methylene blue agar. 



Results on all cultures isolated may be summarized as follows : 



Tentatively regarded as B. coli from appearance of eosin-methy- 

 lene blue agar 122 



Correctly designated as indicated by negative Voges-Proskauer 

 reaction 118 



Per cent, confirmed 96.9 



Tentatively regarded as B. aerogenes from appearance on eosin- 

 methylene blue agar 102 



Correctly designated as indicated by positive Voges-Proskauer 

 reaction 84 



Per cent, confirmed 82.4 



CORRELATION OF VOGES-PROSKAUER AND METHYL-RED REACTION 



In previous work a marked correlation was observed between the 

 Voges-Proskauer and methyl-red reactions. Strains of coli-like forms 

 which were acid to methyl-red characteristically did not give a test 

 for acetyl-methyl-carbinal (V-P negative) ; while those reacting alka- 

 line to methyl-red gave a positive Voges-Proskauer test. These 

 observations were confirmed by Greenfield, 1 Hunter, 2 Clark, 3 Hutton, 4 

 Rettger and Burton 5 and others. 



