20 MASS. EXPERIMENT STATION BULLETIN 426 



(32° to 68°F. or 0° to 20°C.), they carried on additional experimental studies in 

 which it was found that, while all strains studied grew well and rapidly at 59°F. 

 (15°C.), the spores of only three strains germinated at this temperature. Dif- 

 ferent strains varied materially in their temperature relations. It was concluded 

 that foods ma}- become dangerous fairly rapidly when stored at room temperature 

 or under only slight refrigeration, but when kept at less than 50°F. (10°C.), they 

 would remain safe for a considerable length of time. 



It is obvious that low storage temperatures for home-canned foods are most 

 desirable. This would hold true, as a guard not only against botulism, but also 

 against other spoilage bacteria and as a means of better retaining the nutritive 

 value, color, and flavor of all foods. 



Effect of Other Microorganisms on Growth and Toxin Production by 

 Clostridium botulinum 



The presence and growth of other microorganisms in conjunction with CI. 

 botulinum frequently influence the growth and toxin production of the latter. 



Jordan and Dack (1924) and Dack (1926) showed that CI. sporogenes may 

 prevent the development of CI. botulinum, may dinliinish the amount of toxin 

 that is produced, or may cause an early disappearance of the toxin. The growing 

 cells of CI. sporogenes destroyed the toxin of CI. botulinum. Sommer and Glunz 

 (1927) inoculated varying relative amounts of spore suspensions of CI. botulinum 

 and CI. sporogenes into meat, spinach, and asparagus media. Botulinum toxin 

 was formed in all of the meat cultures, irrespective of the presence of CI. sporo- 

 genes. Toxin was produced in spinach only when the spores of CI. sporogenes were 

 exceeded in number by those of CI. botulinum. In asparagus, a poorer medium 

 for toxin formation, the presence of CI. sporogenes had a greater inhibiting effect. 

 In all three media, the strength of the toxin gradually diminished with increasing 

 numbers of CI. sporogenes spores. Stark, Sherman, and Stark (1929) found that 

 B. subtilis reduced the toxin titer of botulinum filtrate. Kayukova and Kremer 

 (1940) reported that CI. botulinum did not grow in mixture with Streptococcus 

 thermophilus and the toxin was gradually destro^'ed. Bacillus mesenterious ruber 

 and B. subtilis activated the growth of CI. botulinum, while Clostridium putri- 

 ficans and CI. sporogenes somewhat depressed toxin formation but did not 

 destroy it. 



It is particularly important to note that the presence of other microorganisms 

 may favor toxin production under conditions which would otherwise repress it, 

 such as in fruits and tomatoes. Bigelow and Cathcart (1921) believed that the 

 formation of toxin in home-canned pears, responsible for a botulism outbreak, 

 had been made possible by the growth of a yeast and a lactic acid producing 

 bacterium. Edmondson, Giltner and Thom (1922) also reported that yeast 

 growth favored toxin formation in foods. Outbreaks of botulism from home- 

 canned tomatoes or fruit are believed to be due to the growth of mold in the 

 product, which creates a favorable environment for the growth of CI. botuhnum. 



According to Townsend (1943) mold growth reduces the acidity of acid foods 

 and brings about a sufficient change in the protein to enable CI. botulinum to 

 grow. Because of this he advised that it was safest ne\'er to use any mold}- 

 canned fruit. 



The above findings point to the fact that, if canned fruit and tomatoes are 

 underprocessed to the extent that mold will grow in them, they may become 



