Pathogenic Bacteria 343 



sometimes for the rest of their hves, and it is of the utmost pubHc 

 importance that such carriers be exckided as food handlers. An 

 arbitrary- designation of three months has been set as the dividing 

 line between convalescent carriers and chronic carriers. 

 Viable tvphoid organisms are excreted by these carriers in their 

 feces, and strict attention must be paid to sanitary practices if the 

 spread of this disease is to be avoided. 



A classic case in medicine is that of Mary Mallon, a cook who 

 was a typhoid carrier. She refused to heed warnings of public 

 health authorities and continued to spread virulent typhoid to 

 unsuspecting persons for whom she prepared meals. The New 

 York Health Department was finally forced to take "Typhoid Mary" 

 into custody, and she remained in detention for three years. The 

 courts upheld the action of the Health Department in this unique 

 case. After promising to give up her occupation as a cook, Mary 

 Mallon was released from detention, and nothing further was 

 heard of her for about five years. When typhoid broke out in a 

 New York City hospital, it was discovered that Mary was the 

 cause of the epidemic. She had found her way back in a kitchen 

 and was spreading her virulent microbes once more. She was 

 taken into custody for a second time, and she finally died after 

 causing over fifty cases of typhoid fever in ten known outbreaks. 

 There is no way of knowing how many other cases she was in- 

 directly responsible for spreading. 



Diagnosis of typhoid depends upon the isolation of the causative 

 organisms from the patient. Blood cultures are generally positive 

 during the first week or ten days of the disease, and stool cultures 

 and urine cultures are positive after ten days. Typhoid agglutinins 

 can be detected in the blood serum by means of the Widal test 

 after about the tenth day of the disease. Disappearance of the 

 microbes from the bloodstream is apparently correlated with the 

 increase in typhoid agglutinin titer. Carriers may retain a high 

 titer indefinitely, and this may sometimes aid in detecting these 

 individuals when repeated stool culture examinations prove nega- 

 tive for Salmonella typhosa. 



Typhoid vaccination induces active immunity. Such vaccines 



