124 PRINCIPLES AND PRACTICE OF MILK HYGIENE 



throat occurring among dairy workers or in their fam- 

 ilies; if persons who have attended diphtheria patients 

 or individuals recovering from the disease are not per- 

 mitted to handle milk or milk vessels until cultures from 

 the throat prove to be free from the bacilli, and if re- 

 turned bottles are sterilized before refilling. Frequently 

 the bacilli are not very virulent. 



The diphtheria bacillus has been demonstrated in 

 milk only a few times, principally because the organism 

 is present in infected milk in small numbers and usually 

 for only a short period. There is no doubt, however, of 

 its transmission by milk. The milk is not changed in 

 appearance by the growth of the organism. The bacillus 

 is not affected by the degree of acidity present in cream 

 ripe for churning, and it may therefore be present in 

 butter and also in other dairy products, although we have 

 no reports of the latter carrying infection. A compara- 

 tively low degree of heat is sufficient to destroy the 

 organism. It is usually killed by a temperature of 55 C. 

 (131 F.),.but occasionally some individuals survive 

 until the temperature reaches 60 C. (140 F.). 



When an outbreak of diphtheria occurs with the 

 characteristics of a milk-borne epidemic, the same pro- 

 cedure should be followed as described under typhoid 

 fever. 



SEPTIC SORE THROAT 



Epidemics of septic sore throat originating from in- 

 fected milk have been reported from England for a 

 number of years and, in recent years, several outbreaks 

 of the disease, affecting thousands of persons, have oc- 

 curred in this country. In some instances the infection 

 of the milk was traced to cows affected with streptococcic 



