TESTS FOR B. COLI IN MILK 



357 



milk, 2 of certified raw milk, and 4 not labelled. We do not 

 wish at this time to lay great emphasis upon the findings of 

 B. coll as distributed among these classes further than to say- 

 that a surprisingly large number of pasteurized samples, namely, 

 10 out of 14, contained B. coli. 



What we do wish to emphasize is, (1), that no evidence was 

 gained of the survival of anaerobes after heating to 56-60° 

 for thirty minutes as shown by the presumptive test in lactose 

 broth, with or without gentian violet; (2), that the use of gentian 

 violet does not prevent the isolation of B. coli from unheated 

 samples. Indeed 3 samples gave positive presumptive tests 



TABLE 1 



* Three samples not tested. 



with gentian violet lactose broth and negative tests with plain 

 lactose broth; in only one of these was B. coli isolated and the 

 presumptive test was negative up to the fourth day. In the 

 other two cases B. coli was not isolated from the sample; had 

 gentian violet not been omitted from the lactose agar plate in 

 these two cases B. coli might have been isolated as in the other 

 case with its use. In no case did a sample yielding B. coli in 

 the presumptive test without gentian violet fail to yield this 

 organism from the presumptive test with gentian violet. 



We note that in 5 positive presumptive tests in gentian violet 

 lactose broth from which streaks made on plain lactose agar plates 



THE JOURNAL OF BACTERIOLOGY, VOL. Ill, NO. 4 



