BACILLUS TETANI 137 



Bacillus tetani produces indol, carbon dioxide and hydrogen sulphide. 



Resistance. Bacillus tetani is slightly more resistant to germicidal agents 

 than the typhoid bacillus, but its spores are very resistant. They survive in 

 5 per cent, phenol and i : 1000 bichloride solutions at 20C. for hours. Steril- 

 ization in a hot-air sterilizer sometimes requires a temperature of i5oC. for 

 several hours. Boiling is said to destroy tetanus spores in 10 minutes, but 

 frequently boiling for an hour or more is necessary. Steam at 15 pounds 

 pressure destroys them in a few minutes. 



Direct exposure to sunlight and air rapidly alters tetanus spores and in the 

 course of 10 to 15 days destroys them. Spores upon the surface of the ground 

 where air and light strike them die in one or several weeks. Upon wood, in the 

 dust and crevices of buildings, where they are protected from light and, to some 

 degree from air, they remain viable and virulent for years. 



Toxin. Bacillus tetani produces a powerful extracellular toxin. The symp- 

 toms and fatalities of tetanus are caused by the filterable toxin called tetano- 

 spasmin. It seems to have an especial affinity for nerve tissues and to travel 

 to the central nervous system along the motor tracts. 



" Tetanolysin " is a separate extracellular toxin produced by the tetanus 

 bacillus. It causes hemolysis of the red blood cells of many animals. 



By repeated injection of sublethal doses of toxin, animals can be immunized 

 against tetanus and the serum of such animals is highly antitoxic. 



Agglutinins are not present in the blood of those infected with bacillus 

 tetani. 



Pathogenesis. Tetanus is a disease having a high mortality. Man and. 

 the horse are especially susceptible; guinea-pigs, mice and rats are very sus- 

 ceptible, rabbits less so; dogs possess a considerable degree of immunity. 



Absence of oxygen, devitalization of surrounding tissue and presence of other 

 organisms are conditions most favorable to infection, hence the disease is usually 

 seen following puncture wounds, extensive traumatism and deep lacerations 

 grossly soiled with street dust, soil or cinders. Bacillus tetani lodges at the 

 point of entry; it does not enter the blood-stream or lymph-stream and does not 

 pass to other parts of the body. The invading organisms are strictly localized 

 and the extracellular toxin they liberate travels along the course of the motor 

 nerves to the motor centers. 



It has been fairly well established that tetanus spores may enter the body 

 and remain dormant at the atrium of infection for weeks, eventually being 

 destroyed or removed from the body through the action of natural /protective 

 forces or as the result of injections of tetanus antitoxin or, after remaining 

 dormant for a number of days or weeks, become active, producing bacilli, 

 toxin and the characteristic phenomena of tetanus. Such activity after quies- 

 cence is favored by a local or general weakening of the natural or normal im- 

 munizing forces as commonly follows trauma, intercurrent infections and 

 certain chemical intoxications. It has been known for a long time that quinine 

 is an activator of tetanus spores and bacilli; that the administration of small or 

 large doses of quinine favors the development of tetanus. 



