88 MEDICAL BACTERIOLOGY 



Shick Test. One of the recent additions to diagnostic tests has disclosed 

 much valuable information in regard to the prevalence of immunity and sus- 

 ceptibility of persons of various ages in civilized communities and promises to 

 be of practical value in the future to determine whether or not any individual 

 is immune or susceptible to diphtheria. 



The test is based on the findings of von Behring and others that if one has 

 as much as ^o un it f antitoxin per cubic centimeter in his blood serum he is 

 immune. An amount of toxin which requires the presence of 3^o unit anti- 

 toxin per cubic centimeter to neutralize it is injected into the skin. If it is 

 neutralized inflammation does not occur. If not neutralized, in 24 to 48 hours, 

 an area of erythema i to 2 centimeters in diameter appears with slight infiltra- 

 tion. Shick recommends the use of %o un it of toxin in o.i cc. sterile water. 



The toxin should not be diluted until the test is to be made; the injection 

 must be into and not beneath the skin, if properly injected a slight swelling and 

 blanching occurs at the point of injection. 



Strong or concentrated toxin should be employed so as to minimize the 

 amount of protein from culture medium injected because this is thought to be 

 responsible for the pseudoreactions at times observed. 



Carriers. Persons who harbor diphtheria bacilli in nose or throat without 

 suffering any injury therefrom are known as carriers. Numerous investigations 

 have shown that most patients continue to have diphtheria bacilli in their nose 

 or throat for i to 2 weeks after the beginning of convalescence from diphtheria; 

 from 0.5 to 5 per cent, continue to be carriers for weeks or months; and from 

 o.i to 3 per cent, of persons, who, so far as known, never had diphtheria, harbor 

 .virulent bacilli at times or continuously. These carriers are most numerous 

 among nurses and physicians attending diphtheria patients. 



Pseudodiphtheria bacilli are occasionally or continually present in the nose 

 or throat of from 10 to 80 per cent, of all people in numerous localities. 



Obviously it is necessary to determine that a suspected or probable carrier 

 is free of diphtheria bacilli before release from quarantine and that organ- 

 isms obtained from a suspect be tested for virulence as well as examined 

 microscopically. 



Kolmer and Woody recommend the following virulence test of organisms 

 isolated from convalescents and suspected carriers: 



(.4) i. Obtain culture from patient on Loeffler's blood serum. 2. Trans- 

 plant to 0.2 per cent, glucose broth -f-o.8 reaction. 3. Incubate broth 72 

 hours. 4. Inject, subcutaneously, an amount of the culture equal to ^ per 

 cent, the test animal's weight use 250 to 300 Gm. guinea-pigs. 



(-B) i. Procure a good 24-hour-old culture from suspected patient on Loeffler's 

 medium. 2. Wash off growth with 10 cc. of salt solution. 3. Inject 4 cc. of 

 this salt solution suspension subcutaneously into a 250 to 3oo-Gm. guinea-pig. 



The test animal is observed for 4 days and if inflammation at point of in- 

 jection and toxemia occur the organism is considered virulent. 



