Pasteurization of Milk Containing the Organism of Q Fever

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Abstract
The thermal-resistance of Coxlella burnetii in cow''s milk was investigated using both laboratory and commercial equipment. The number of rickettsiae apt to be found in the milk of infected cows, as shown by surveys, was used as the test population. Two passages in guinea pigs, inoculated by the intraperitoneal route, was the method used to determine the presence of small numbers of viable rickettsiae in the heated milk samples. Heating for 30 minutes at 143[degree]F is not sufficient to eliminate all the viable C. burnetii from whole raw milk. Heating at 145[degree]F for 30 minutes will accomplish this with an appreciable margin of safety. Results obtained using a vat-type commercial pasteurizer confirm this finding. Investigation at higher temperatures of the thermal-resistance of this organism suspended in whole raw milk strongly supports the presently recommended standards of 161OF for 15 seconds in the holding tube of a commercial high temperature-short time pasteurizer as adequate to eliminate the viable organisms.