SIGNIFICANCE OP COLON COUNT IN MILK. 13 



A study was also made of 56 samples produced under conditions in 

 which the cows were very dirty and the barn was cleaned only once 

 or twice a week. The utensils were sterilized so that they would play 

 no part in the contamination, thus demonstrating the extent of con- 

 tamination by the colon-aerogenes group which might take place in a 

 filthy barn. Of the 56 samples of milk produced under these condi- 

 tions only 6, or 10.7 per cent, showed organisms of the colon-aerogenes 

 group in 1/100 of a cubic centimeter. The range of these organisms 

 was from 100 to 400 and averaged 183 per cubic centimeter. The 

 average total count of the 56 samples was 36,541 per cubic centi- 

 meter. This at first thought might seem low in view of the filthy 

 conditions of production described. The work of Ayers, Cook, and 

 Clemmer (1), however, has shown that large numbers of bacteria are 

 not generally introduced through manurial filth even under extreme 

 conditions, but come largely from unsterilized utensils. 



An analysis of 84 samples of milk produced under the same dirty 

 conditions as previously described but with utensils which were not 

 sterilized showed that 24 samples, or 28.6 per cent, contained organ- 

 isms of the colon-aerogenes group in 1/100 cubic centimeter. The 

 utensils in this case were washed in hot water containing washing 

 powder within one hour after milking, rinsed in clean, cold water, and 

 allowed to stand inverted until the next milking. The colon count 

 of the 24 samples which showed positive results in 1/100 of a cubic centi- 

 meter ranged from 100 to 28,400 per cubic centimeter. Only one 

 sample ran over 2,000, that one being 28,400. Including this high 

 count the average would be 1,717, while leaving out this one high 

 count the average for the remaining 23 samples would be 557 per 

 cubic centimeter. These figures indicate clearly that unsterilized 

 utensils play a prominent part in contamination of milk by the colon- 

 aerogenes group. It will be noted in Table 7 that in the milk pro- 

 duced in unsterilized utensils the colon count was almost three times 

 higher and the total count also higher than in the milk produced in 

 sterilized utensils. In both cases the barn was equally dirty. 



The manner in which the utensils are cleaned plays a very im- 

 portant part in the contamination of milk by organisms of the colon- 

 aerogenes group, which is clearly shown in the last line of Table 7. 

 The milk was produced in the same dirty barn as just mentioned, but 

 the drainings were allowed to remain in the utensils for 8 hours, after 

 which they were washed in hot water containing washing powder. 

 Of the 28 samples produced under this condition 20, or 71.4 per cent, 

 showed colon bacilli in 1/100 of a cubic centimeter. They ranged from 

 100 to 1,800, averaging 750 per cubic centimeter, and were no higher 

 than in the milk produced in the previous experiment, in which 

 the utensils were washed immediately, but a much greater percentage 

 showed organisms of the colon-aerogenes group than in the previous 

 case. 



