The Application of Modern Techniques to the Detection of a Typhoid Carrier

IHE search for satisfactory methods of isolation of Salmonella typhi and Salmonella paratyphi B from water, contaminated with sewage, was greatly advanced when Wilson and Blair (1927) introduced their glucose-sulphite-iron-bismuth brilliant green medium. Further help came with the development of the selenite F medium of Hobbs and Allison (1945a). The next great advance was the description by Moore (1948) of a successful method of sampling sewage and sewage polluted water during a search for carriers of Salm. paratyphi B. This consisted in placing a g,auze swab in the sewers for two to five days and then culturing the entire specimen in selenite F medium and subculturing on to Wilson and Blair's medium. Soon after this Moore (1930) extended the use of his technique to a search for Salm. typhi, and Lendon and Mackenzie (1951) further demonstrated the great value of the method in the search for enteric carriers. The present paper describes the prolonged, but finally successful, search for a typhoid carrier, who proved to be the source of infection of nine cases of typhoid fever over a period of four years, using the methods outlined above, and it tries to show how easily errors and misinterpretations of results can cause confusion and (lelay in finding the carrier. In 1931 three cases of typhoid fever were notified in and around Belfast, all in boys aged 11 to 13 years. After questioning these boys, it was thought that they had probably been infected wvhile playing in the vicinity of Stream I (see sketch map). Many samples of this stream and the effluents from the septic tanks which discharge into it were taken by the Moore swab technique. All were negative for Salmti. typhi. Six weeks later a further case of typhoid fever came to liglht. This patient had been working in the wood through which Stream I flows. Enquiries of this man revealed that there had been, working in the same gang, a labourer who was known to have had enteric fever in 1945. Latrines were not provided for the workmen, and it was felt, at the time, that this known, old case of typhoid fever was the probable source of infection. One sample of facces was obtained from him, but after that he refused to cooperate. This one sample proved, however, to be negative for Salm. typhli. Blood for Vi antibody tests could not be obtained. Tlhere the matter rested, …