114 MEDICAL BACTERIOLOGY 



During the first weeks of typhoid fever the reaction is often negative; in rare 

 cases the reaction is negative until the second or third week of the disease there 

 are a few reported cases in which the Widal test has been negative throughout 

 the disease; occasionally diseases other than typhoid fever give a positive 

 reaction. 



Agglutination tests made with specific sera and suspected organisms, when 

 properly performed, give accurate results in the vast majority of cases. 



Specific agglutinating sera often contain group-agglutinins; that is, they 

 will agglutinate one or several members of the typhoid-colon group in addition 

 to the particular organism employed to produce them. In practically all cases 

 the power to agglutinate other organisms is much less than the power of agglu- 

 tinating the particular bacillus which produced them. 



Errors can therefore be avoided by determining the highest dilutions in 

 which a serum exerts a group-agglutinating action and those dilutions in 

 which its action is specific. 



BLOOD CULTURES 



In typhoid fever, paratyphoid, food poisoning, colon septicemia and infec- 

 tions with other members of the typhoid-colon group of organisms in which the 

 clinical course is that of typhoid fever, the offending organism can be obtained 

 from the patient's blood in all cases during the first week or two of the disease 

 and frequently later. In severe prolonged cases of typhoid fever the organism 

 can usually be obtained from the blood later than the second week of the 

 disease. 



TECHNIQUE 



The night before operation the patient's arm and forearm should be washed 

 with soap and water, alcohol and 1:1000 bichloride, and covered from 4 inches 

 below to 4 inches above the elbow with a moist bichloride dressing and sterile 

 bandage. 



A flask containing at least 200 cc. of plain bouillon having a reaction of -f-i-o 

 or +1.5 is taken to the bedside. This culture medium must, of course, be 

 sterile. A sterile lo-cc. glass syringe and needle in a sterile container is also 

 required. 



The operator scrubs his hands with soap and water and then with alcohol 

 and dries them on a sterile towel. The dressings are removed from the patient's 

 arm and an area of about an inch in diameter over the most prominent vein 

 is painted with tincture of iodine. A crystal of carbolic acid is touched to the 

 spot through which the needle will be inserted. The needle is firmly fastened 

 to the syringe and thrust into the vein. At least 2 cc., better 5 cc. of blood is 

 drawn into the syringe. The needle is withdrawn from the vein, guarded from 

 contamination or contact with anything, and the contents of the syringe 

 emptied into the culture medium without any previous attempt to remove the 

 needle from the syringe. 



When the plug is removed from the flask and until it is replaced, contamina- 



