J. RUSSELL ESTY 287 



arbitrary laboratory tests apply only to the conditions under which they were made. 

 They are valuable in establishing certain fundamental principles, but in making defi- 

 nite regulations for commercial practice the work must be done under actual existing 

 conditions. 



THE DESTRUCTION OF SPORES OF CI. tetani 



The variations in the heat resistance of the spores of CI. tetani may be cited as 

 another example. Some of the published reports may be briefly summarized as fol- 

 lows: 



Kitasato/ who isolated the bacillus, stated that the spores survived moist heat at 80° C. 

 (176° F.) for I hour but were destroyed in steam (100° C.) (212° F.) in 5 minutes. Vaillard 

 and Vincent^ observed that the spores resisted 80° C. for 6 hours, 90° C. for 2 hours, 100° C. 

 for from 3 to 4 minutes, were not always destroyed in 5 minutes, but never resisted more than 

 8 minutes. Levy and Bruns^ report that CI. tetani spores were not destroyed in 8| minutes 

 at 100° C. and that few survived 15 minutes, but they were killed in 30 minutes. Anderson' 

 reports the resistance of one strain isolated from commercial gelatin as 20-30 seconds at 

 100° C. Tuck'5 claims that no spores of tetanus can resist boiling over 20 minutes. Falcioni" 

 impregnated gelatin with spores of tetanus grown in agar or broth for 10 to 1 2 days and found 

 that these spores survived 2\ hours but not 3 hours in steam (100° C.) in 2, 5, and 10 per cent 

 gelatin. Smith's" experiments showed that tetanus spores survived 100° C. for 20 minutes 

 regularly, 40 minutes usually, and 60 minutes occasionally. In one case cultures contained 

 viable spores after 70 minutes at 100° C. Von Hibler^ observed variations in the heat resist- 

 ance of seven different strains and found that in one case spores survived 2\ hours at 100° C. 

 Becker^ reported the death-point of two strains as 2 and 3 hours, respectively, in boiling water 

 when heated in brain or alkaline reaction. 



Based on a study of twenty-four strains of CI. tetani, Esty and Meyer'" found the heat 

 resistance of tetanus spores to vary at 100° C. from 15 to 90 minutes, the average survival 

 time being 25 minutes. At 105° C. the heat resistance varied from 3 to 25 minutes and showed 

 an average survival time of 9.2 minutes. The spores were produced either in pea peptic- 

 digest broth, brain medium, double-strength veal-infusion peptic-digest gelatin, or casein 



M 

 broth, and were heated in a — phosphate solution, pH 7.0, with the exception of those 



produced in the brain medium. 



These results indicate, as in the case of B. tuberculosis, that strains of CI. tetani exist, 

 spores of which vary widely in their resistance to moist heat. Smith," in reviewing the liter- 

 ature on the thermal death-point of tetanus spores, comments as follows: "It would be 

 necessary to know the tendency to spore formation in different media and at different 



■ Kitasato, O.: Ztschr.f. Hyg., 7, 225. 1889. 



^ Vaillard, L., and Vincent, H. : Ann. de I'lnst. Pasteur, 5, i. 1891. 



3 Levy, E., and Bruns, H.: Grenzgeb. d. Med. in Ckir., 10, 235. 1902. 



1 Anderson, J. F.: U.S. P.H. and Mar. Hosp. Service, Hyg. Lab. Bull. p. 1902. 



5 Tuck, G. L.: /. Path fir Bad., 9, 38. 1903. 



^ Falcioni, D.: Ann. d'ig. sperimentale, 14, 319. 1904. 



7 Smith, T.: J. A.M. A., 50, 929. 1Q08. 



* von Hibler, E.: Untersuchungen iiber die pathogenen Anaeroben, p. 211. Jena: G. Fischer, 1908. 



9 Becker, L.: Centralbl.f. Bakteriol., Abt. I, 84, 71. 1920. 



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



" Smith, T.: op. cit., p. 932. 1908. 



