448 THE BACTERIA OF FOOD POISONING 



Type-A strains and nearly all, if not all, of the strains of Type B are definitely 

 proteolytic. The heat resistance of the spores of Types A and B is greater than that 

 of any other anaerobes yet tested.' The maximum heat resistance as determined by 

 a study of one hundred and nine strains heated in a phosphate solution of pH 7.0 



is as follows:^ 



4 minutes at 120° C. 



10 minutes at 115 



32 minutes at no 



100 minutes at 105 



330 minutes at 100 



The thermal death-point of Type C strains is reached at temperatures considerably 

 lower, and it is perhaps for this reason that in the outbreaks of botulism in the United 

 States— which are mostly due to heat-preserved foods — Type C has not been found. 

 The thermal death-point of van Ermengem's original strain (Belgium) was reported 

 to be reached at exposure to only 80° C. for one-half hour. It seems possible that in 

 Europe, where such foods as sausages and smoked meat and fish have figured largely 

 in botulism outbreaks. Type C may have been concerned. Besides the differences 

 in heat resistance, toxicity, and proteolytic power, agglutinative and other differences 

 distinguish the three types. 



In human food poisoning in the United States Type A botulism seems to be by 

 far the most important. Geiger, Dickson, and Meyer^' record the isolation and identi- 

 fication of Type A in nineteen outbreaks, of Type B in three. It is noteworthy also 

 that the majority of reported botulism outbreaks have been in those regions — Rocky 

 Mountain and Pacific Coast states — where CI. botulinum, Type A, occurs most 

 abundantly in soils. In samples of European soils Meyer found Type B but not Type 

 A. It is remarkable that in the United States the highly toxic Type A is found most 

 abundantly in the uncultivated soils of remote, thinly settled regions. The relation 

 of the three closely allied but immunologically distinct types is not understood. It 

 has been surmised that the B type may be the degenerate descendant of the more 

 highly toxic and resistant A type, but proof of this connection is still lacking. 



Since the spores of CI. botulinum are relatively common in soil in many parts of 

 the world and must adhere frequently to vegetables used for preservation, and since 

 also the temperatures used in the home canning of food have in the past been often 

 inadequate to insure complete sterilization, it might be expected that botulism would 

 have occurred more commonly than has been the case. How can the rarity of the 

 disease be explained? It is obvious that the factors necessary to bring about the 



(Mono. 8, Rockefeller Inst. Med. Research, p. 117. 191 8), who has also given a valuable review of the 

 more recent work on pathogenicity, toxicology, and immunology (/. Frev. Med., i, 71. 1926). The 

 epidemiology of botulism has been comprehensively summarized with much new material by J. C. 

 Geiger, E. C. Dickson, and K. F. Meyer (Ptib. Health Bull. 127, U.S. Pub. Health Service, p. 119. 

 1922). Numerous special articles by Meyer and his collaborators have appeared in the Journal of 

 Infectious Diseases (cf., e.g., 31, 501-663. 1922). 



' Esty, J. R.: Am. J. Pub. Health, 13, 108. 1923. 



^ Esty, J. R., and Meyer, K. F.: /. Infect. Dis., 31, 650. 1922. 



^ Geiger, J. C, Dickson, E. C, and Meyer, K. F.: loc. cit. 



