340 Microbes and You 



suggested that since the organisms occlude blood vessels, the death 

 of the individual may be caused by sheer numbers of the microbes 

 present in the infected host. 



Anthrax spores are able to resist 140° C. for three hours of dry 

 heat, and 100° C. live steam for five to ten minutes. Improperly 

 sterilized shaving brushes have caused a number of cases of anthrax 

 of the face. Inhalation of the spores from wool can cause fatal 

 ANTHRAX PNEUMONIA ( wool-sortcr's discasc ) . About 80% of infected 

 animals succumb to the disease. Vaccines prepared from killed 

 cultures are ineffective in preventing anthrax in animals, but by 

 growing the bacilli in broth at temperatures of 42-43° C. for 

 prolonged periods, the organisms are attenuated and fail to pro- 

 duce spores. Injection of these modified cultures provides active 

 immunization. This technic was developed by Pasteur, and it is 

 still the accepted method for preparing such vaccines. 



CLOSTRIDIUM TETANI 



Rods measuring 0.4—0.6 by 4.0-8.0 microns, with rounded 

 ends, found in singles or pairs, and sometimes in chains. Gram 

 positive. Spherical terminal spores. Form potent exotoxin. 

 Normal habitat in soils, human and horse intestines, and in feces. 

 Anaerobes. Optimum growth temperature 37° C. Cause of tet- 

 anus (lockjaw). 



These anaerobic rods were discovered in 1889 by Kitasato from 

 a case of tetanus, and he reported that the microbes produced a 

 powerful exotoxin. Together with von Behring, he developed an 

 effective antiserum to neutralize the destructive action of the true 

 toxin liberated by Clostriditim tetani during its anaerobic growth. 

 The poison is called tetanospasmin, and it causes a contraction 

 of the skeletal muscles. In pure form tetanus toxin will kill a man 

 when as small a dose as 0.00025 gram is injected, but this same 

 toxin is non-poisonous when taken by mouth. 



Owing to the anaerobic requirements of these bacteria, deep, 

 dirty, puncture wounds are particularly favorable for the growth 

 of Clostridimn tetani, which remain localized and give off their 

 powerful poison which is carried to other parts of the bodv where 



