130 



ESSENTIALS OF BACTERIOLOGY 



Methods of Diagnosis. A small piece of exudate or some 

 secretion from pharynx, tonsil, or nares is obtained on a ster- 

 ile cotton swab and transferred, as soon as possible, to the sur- 

 face of two or more blood-serum tubes (if these are not avail- 

 able, the swab should be placed in a sterile test-tube or bottle, 

 and sent to the laboratory at once). The inoculated tubes 

 are placed in the incubator at 37 C, and examined in twelve 

 hours. If a growth is visible, a slide is made and stained 



Fig. 56. Bacillus diphtheriae, from a culture upon blood-serum (Xiooo) 

 (Frankel and Pfeiffer). 



with Loffler's and Neisser's stain, and if bacilli are present, 

 with characteristic granules, the diagnosis of diphtheria is 

 most probable. Negative results are not to be depended on. 

 The use of antiseptics, gargles or the failure to obtain a portion 

 of the exudate may give a negative culture result in a case of 

 diphtheria. If the symptoms are suggestive, it is best to use 

 antitoxin and isolate the patient, notwithstanding a negative 

 report from the laboratory. If there are no clinical signs, 

 the growth should be tested for toxicity by inoculating a 



