DIAGNOSIS OF TYPHOID FEVER AND FOOD-POISONING INFECTIONS 115 



tion of both the plug and culture medium must be guarded against. As soon as 

 the blood is in the flask and the plug replaced, the flask is shaken for several 

 minutes to thoroughly mix the blood and culture medium and to prevent clot- 

 ting. During the shaking and transportation care must be observed not to 

 bring the contents of the flask into contact with the cotton plug. 



The flask is taken directly from the bedside to the laboratory and placed 

 an incubator at 37C. 



After 12 hours the flask is examined for bacterial growth; if not discovered 

 the flask is replaced in the incubator and again examined every 6 hours until 

 growth is observed, or until 72 hours have passed. When the flask remains 

 sterile after 72 hours it is strong evidence that the infection is not due to any 

 of the typhoid colon group of bacteria. Evidence of other infectious disease, 

 especially tuberculosis, should be sought for. 



The method of examining the culture for growth is as follows: 



Shake the flask, remove the plug, take out a drop of the fluid with a sterile 

 platinum loop, replace the plug, place the drop of fluid on a clean cover glass 

 and suspend on a hanging-drop slide. Examine the drop under the microscope; 

 if no organisms are observed remove and examine several more drops. If a 

 motile bacillus appears it is probably the typhoid, paratyphoid A, paratyphoid 

 B or colon bacillus. To determine, plant a loopful of the culture in litmus milk, 

 make a stab culture in litmus lactose agar and another in litmus glucose agar. 

 Place these tubes in an incubator at 37C. and, after 18 hours, inspect for char- 

 acteristic reactions. 



Instead of making stab cultures in litmus lactose agar and litmus glucose 

 agar, fermentation tubes, containing litmus glucose bouillon and litmus lactose 

 bouillon, may be planted. 



These three subcultures will suffice, in the majority of cases, to disclose the 

 nature of the offending organism. The reaserch may be carried further by 

 making subcultures in Dunham's solution and testing for indol, planting in 

 litmus bouillon containing saccharose, maltose, mannite, levulose, galactose, 

 dulcite, raffinose, arabinose and inulin. Agglutination tests with specific sera 

 may be made and films stained by Gram's method should be examined. 



In summing up, it may be stated that in suspected cases of typhoid fever the 

 laboratory diagnosis should consist of both a Widal test and blood culture, with 

 the expectation that one or the other be positive in typhoid; that a negative 

 Widal, together with the occurrence of a motile, Gram negative organism in the 

 culture from the blood is suggestive of paratyphoid or colon infection, especially 

 if occurring after the first week of the disease; that the true nature of the infec- 

 tion can be determined, in most cases, when a culture is obtained from the blood, 

 by making subcultures in three different media, litmus milk, litmus lactose agar 

 or litmus lactose bouillon and litmus glucose agar or litmus glucose bouillon; 

 that repeated failure to obtain either a positive- Widal or blood culture in a sus- 

 pected case of typhoid fever, indicates infection with an organism not belonging 

 to the typhoid-colon group, usually the tubercle bacillus. 



