482 STATS BOARD OF AGRICULTURE. 



THE INFLUENCE OF THE PRODUCTS OF LACTIC ORGANISMS 



UPON BACILLUS TYPHOSUS. 



This study was iindert.akeii primarily for tlie piir])ose of establishing 

 the maximum longevity of thie typhoid bacillus in sour milk, but from 

 necessity, it has involved problems of technique. 



Previous investigations have dealt mostly with the longevity of B. 

 t}fi)hosiis in sweet milk; a few only, with sour milk, buttermilk, butter 

 and cottage cheese. 



Concerning the longevity of B. typhosus in sour milk, buttermilk, etc., 

 BartheP says : ''Typhoid bacteria increase in milk and remain alive for 

 twenty-five days Avithout a decrease in number due to the formation of 

 acid in the milk," and further "they themselves contribute to this acid 

 production." "In butter, typhoid bacteria are found after ten days, 

 especially in butter which is strongly acid, as this enclosed sour brine 

 is a good nourishing medium." 



On the other hand, Bassenge^" has attempted to show that during the 

 process of cream ripening, the lactic acid produced by fermentation 

 organisms serves to diminish the number of typhoid bacilli present in 

 the cream ; and after the cream is thoroughly ripened and churned, the 

 butter after being Avorked A\'ill contain no living ty])hoid organisms." 



The greater number of investigators agree that the lactic fermenta- 

 tion in milk has a deleterious effect, both upon the vitality and long- 

 evity of the tyi>hoid bacillus. According to Bassenge,^" Behla^ and 

 others, when milk, buttermilk, etc., reaches 0.4 per cent lactic acid, ty- 

 phoid bacilli are killed within 24 hours, although Friinkel and Kister 

 found them living even after 48 hours. 



It has been the purpose of the author to deal with the life of B. fi/- 

 pliosus in sour milk only, limiting the ])roblem in the first experiments 

 to the ascertaining of the amiount of lactic acid necessary to check, 

 diminish the number oi, or entirely destroy them. 



In a preliminary test, measured portions of lactic acid were added to 

 a definite volume of sweet milk in order to ])roduce varying amounts 

 of acid milk in which (o grow the (yjdioid organisms. After a thorough 

 test, this procedure was i)ronounced unsatisfactory as the addition of any 

 (|uautily of acid diluled thie milk and produced a curd quite dissimilar 

 to lliat ]>i'odu(ed by laclic organisms; then, too, other products of lactic 

 fermcnlalioH would not be present in this case to inlluenee resuUs; also, 

 when adding i)ure lactic acid to milk a certain amount combines with the 

 casehi, leaving only a portion of Ihe lotal acid free to act ui)on the 



organisms. 



Exj^criment I. 



LITMUS LACTOSE CALCIUM CARBONATE AGAR MEDIUM. 



In (he following test, the lactic organisms Avere allowed (o ]»roduce 

 their own acid and />. tj/pJiosiis was grown in association wilh it in 

 sterile milk. I'lafes were made fi-oni time to time as the milk was 

 souring to determine the increase or decrease of typhoid bacilli. 



