518 



PATHOGENIC MICROORGANISMS 





colonies which can be easily fished and again transferred to Loeffler 

 tubes or any other suitable medium. 



Diagnosis. Cultures from suspected throats are taken on Loeffler 's 

 blood serum medium and incubated at 37.5 C. for 12 to 18 hours. At 

 the end of this time morphological examination by staining with Loef- 

 fler 's alkaline methylene blue and by some polar body stain like that 



of Neisser is carried out. Occa- 

 sionally direct smears from the 

 throat may show the bacilli, but it 

 is rarely possible to make a satis- 

 factory diagnosis in this way. 



"Williams has pointed out that in 

 throat cultures in which the diph- 

 theria bacilli are few in number 

 it is of advantage to inoculate a 

 ^ u ^ e ^ asc itic broth with the 

 mixed culture. The diphtheria ba- 

 cilli will appear in eighteen to 

 twenty-four hours as a pellicle on 

 the surface. A portion of this 

 pellicle may then be plated on 

 ascitic agar and isolated in pure 

 culture from the colonies. 



Pathogenicity. Bacillus diphtheria? causes a more or less specific 

 local reaction in mucous membranes, which results in the formation of 

 the so-called * ' pseudo-membranes. ' ' When these are characteristically 

 present, infection with this bacillus should always be suspected. The 

 consequent disease depends, in part, upon the mechanical disturbance 

 caused by these false membranes and, in part, upon the systemic poi- 

 soning with the toxin which the bacilli produce. Although the diph- 

 theria bacillus has been found after death in the spleen and liver, we 

 have no data which would justify the assumption that a true diph- 

 theria-septicemia may occur during life. It is probable that in those 

 cases which Baginsky * has called the septicemic form of diphtheria, 

 Bacillus diphtheria? has merely opened a path by which accompanying 

 streptococci have gained access to the lymphatics and the blood stream. 

 The most frequent sites of diphtheritic inflammation are the mucous 

 membranes of the throat, larynx, and nose. They have also been 



FIG. 106. COLONIES OF BACILLUS 

 DIPHTHERIA ON GLYCERIN AGAR. 



Baginsky, "Lehrbuch d, Kinderkraiikheiten," 



