24 



Scientific Proceedings (ioi). 



12 (1472) 



Serologic method for detecting infection in foods. 



By J. Bronfenbrenner and M. J. Schlesinger. 



[From the Department of Preventive Medicine and Hygiene, Harvard 



Medical School.] 



The isolation and identification of the infecting organism in con- 

 taminated foods is usually beset with difficulties and success- 

 ful results are not the usual outcome. Negative findings often 

 are due to the fact that it is impossible to examine the whole sample 

 of the incriminated food bacteriologically. Since the pathogenic 

 bacteria are usually few in number, and are not distributed 

 throughout the food, it is more or less a matter of luck if one suc- 

 ceeds in isolating an organism which might justify the suspicions. 

 If one attempts to increase the number of the specific bacteria 

 by enrichment through incubation, he at the same time increases 

 the number of saphrophytes, and thus adds to his difficulties. 

 We find that the entire sample of suspected food can be advan- 

 tageously analyzed for the presence of any suspected organism, 

 or their split products (in addition to an attempt to isolate in- 

 dividual bacteria), by the following procedure. 



The whole of the sample of food is chopped up and an extract 

 made from it. This extract is concentrated so that all the speci- 

 fic bacterial protein is collected in a very small volume of liquid. 1 

 This concentrated solution is then tested against a set of specific 

 immune sera. We have been able to detect by this method the 

 presence of B. botulinus protein in 20 gram samples of artificially 

 inoculated food, where the concentration of toxin was so small that 

 it would have required giving at least 7 grams by mouth or 1.3 

 grams by injection into a mouse of 15-20 grams to obtain a positive 

 result. 



This method enables one to determine the presence of a sus- 

 pected organism in contaminated food within 24 hours after 

 receiving the specimen. It is, of course, necessary to have on 

 hand a collection of specific sera of high titer. 



1 J. Bronfenbrenner and M. J. Schlesinger, Jour. Med. Res. (in press). 



