CHAPTER XVIII 

 PSEUDODIPHTHERIA BACILLI 



There are a number of organisms, not pathogenic, which are similar to the 

 diphtheria bacillus morphologically, in staining and growth on culture media. 

 "They have been found in pus, milk, urine and infectious processes resembling 

 the true diphtheria bacilli" (Rosenberger). 



"Differentiation is never difficult" (Hiss and Zinsser). "Bacillus diph- 

 theriae forms acid from dextrin, not from saccharose; Bacillus xerosis from 

 saccharose not from dextrin; Bacillus Hoffmanni does not form acid from either" 

 (Hiss and Zinsser). 



Hoffman's bacillus is found in the throat of healthy people, not infrequently, 

 especially among school children in poor districts. Morphologically it is said 

 to be shorter than the diphtheria bacillus and more uniform in shape. It is 

 also claimed that upon staining Hoffman's bacillus does not show the irregular 

 or band-like staining common to the diphtheria bacillus and when stained by 

 Neisser's method the entire bacillus is brown, no blue staining granules visible. 



Pseudodiphtheria bacilli have a very wide distribution. They are frequently 

 found as secondary invaders in chronic suppurative processes exposed to air. 

 They are occasionally discovered in soil and on various utensils. They have 

 been regularly obtained from the infected tissues in Hodgkin's disease, and are 

 believed by some to play a part in this disease. As to whether they constitute 

 the specific factor of Hodgkin's disease is a mooted point; the preponderance of 

 evidence being against it. 



Growth. On agar, blood serum, gelatin and bouillon the growth of Hoff- 

 man's bacillus is similar to bacillus diphtheria, but more luxuriant. In contrast 

 to the diphtheria bacillus it does not acidulate media containing any of the 

 sugars. 



Pathogenesis. Hoffman's bacillus does not produce extracellular toxin, 

 does not kill guinea-pigs nor rabbits and is not pathogenic to man. 



The xerosis bacillus is most often found upon the conjunctiva, both in health 

 and when the eye is the seat of disease. In morphology and staining it resembles 

 the diphtheria bacillus even more closely than Hoffman's bacillus. 



Growth. The xerosis bacillus may be cultivated on any of the media upon 

 which the diphtheria bacillus grows; its growth is finer, less abundant but 

 similar to that of the diphtheria bacillus. It forms acid on saccharose, but not 

 on dextrin. 



Pathogenesis/ The xerosis bacillus is not pathogenic for man, guinea- 

 pigs nor rabbits. It does not form toxin. 



Diagnosis. With few if any exceptions diphtheria and pseudodiphtheria 

 must be thought of and a differentiation made whenever an organism presum- 



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