8l2 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



DIPHTHERIA* 

 Bacterium diphtheria 



The disease is epidemic in all large communities especially in Europe 

 and America. It is, however, almost absent from tropical regions. 

 Epidemics and pandemics occur in cycles. Essentially diphtheria is a 

 disease peculiar to man. Avian diphtheria, however, is known, al- 

 though seemingly due to another cause, and on rare occasions natural 

 infection has been found in the horse. 



The period of incubation is said to be two to five days. 



In man the disease usually begins with lassitude and fever followed 

 in a few hours by "sore throat." The inflamed area on the pharyngeal 

 wall, tonsils, larynx or wherever it may be becomes in typical cases the 

 seat of degenerative changes in the epithelium and underlying tissues 

 with abundant fibrinous exudation resulting in the formation of a com- 

 paratively tough membrane or pseudo-membrane, which is a striking 

 and characteristic feature of the disease. This local lesion is almost 

 always found on mucous membranes though occasional instances of 

 infection of wounds have been noted. 



In connection with wound infection it should be mentioned that 

 organisms morphologically resembling the true B. diphtheria occur 

 upon the body surfaces and are commonly called "diphtheroids." 

 They are of some importance because occasionally they have to be 

 distinguished from B. diphtheria by culture and animal inoculation, 

 and secondly, while of doubtful pathogenicity, they are held by some 

 to be responsible for a certain indolence in the healing of wounds. In 

 an investigation by Col. Adami and others in the Canadian army it 

 was found that in some localities as many as 33 per cent of war wounds 

 were infected with diphtheroids of at least four different types, while 

 true B. diphtheria occurred in less than 0.6 per cent. 



The bacterium of diphtheria was described in 1883 by Klebs in 

 sections of typical membranes. The organisms were isolated and dif- 

 ferentiated in 1884 by Loeffler, who was able to fulfill Koch's postulates 

 for pathogenic microbes. Accidental infection of the human being has 

 happened in the laboratory and confirmed the findings of animal inocu- 

 lation. The success of antitoxin treatment is further evidence of causal 

 relationship. 



* Prepared by Edward Fidlar. 



