26 



BULLETIN 809, U. S. DEPARTMENT OF AGRICULTURE. 



RESISTANCE OF AMERICAN FOULBROOD SPORES TO HEAT WHEN SUSPENDED IN 



HONEY 



The effects of heating American fonlbrood spores suspended in 

 water are shown above. When suspended in honey a different degree 

 of resistance is to be expected. The technique used to obtain facts 

 relative to such resistance is quite similar to that described (p. 22) 

 for the experiments in which the spores were heated in aqueous sus- 

 pensions; instead of water, however, the spores were suspended in 

 honey ^ or honey diluted with water. For testing whether or not the 

 spores had been killed by the heating, cultures were used in some 

 instances and bees in others. 



In Table V are summarized some of the results obtained when the 

 spores suspended in honey diluted with an equal volume of water 

 were heated and tested by cultures: 



Table V. — American foulbrood spores heated in diluted honey ^ 



Temperature. 



Period of 

 heating. 



°C. 



"F. 



Minutes. 



98 



208 



10 



98 



208 



10 



98 



206 



20 



98 



208 



20 



98 



208 



20 



100 



212 



10 



100 



212 



20 



101 



214 



8 



101 



214 



10 



102 



216 



8 



103 



217 



3 



104 



219 



3 



105 



221 



3 



Origin of sample. 



Cultural results. April-May, 1915. 



Nebraska 



New York 



do 



Nebraska , 



Illinois 



New York 



do 



Washington State. 



Colorado ,.. 



Cuba 



Wasiiington State, 



do 



Cuba 



Numerous spores not killed. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 

 About 600 spores not killed. 



» The altitude of the laboratory in Washington being nearly sea level the boiling temperature of water 

 is almost 100° C. The higher temperatures recorded in this table and the following one were obtained 

 by immersing the capsule containing the suspension in a solution of sodium chlorid and other salts. 



Table V shows that numerous spores were alive after being heated 

 in a suspension of honey diluted with equal parts of water for 20 

 minutes at 100° C. The spores of American foulbrood are not 

 destroyed by heat as readily, therefore, when suspended in diluted 

 honey as when suspended in water. 



Experiments were made in which the spores were heated suspended 

 in undiluted honey and tested by the cultural method. Table VI 

 indicates the nature of the results obtained: 



1 The honey used was purchased at the majket in sealed cans and was from the crop of the year preceding 

 the experiments. 



