Factors influencing the results of blood culture in enteric fever

Abstract

1. The results of 192 blood cultures in an epidemic of enteric fever are analysed. The epidemic was caused by a double enteric infection with Salm. typhi (Vi-phage type T) and Salm. paratyphi B (Vi-phage type ‘Dundee’).2. All of sixty –five cultures between 102 and 104∘ F. were positive, and a significant number of positive cultures at lower body temperatures were obtained. Three out of four cultures, taken when the temperature was subnormal, were positive. In seventy–one out of seventy–six cases (93·4%) a positive blood culture was obtained.3. The highest percentage of positive isolations was obtained in the second week of disease. In the severe cases the highest percentage occurred in the third week. The reasons for this, and the findings of previous studies, are discussed.4. No difficulty was encountered in obtaining positive blood cultures in previously inoculated individuals.5. The average period of incubation of the cultures, required to produce a positive result, was 4–5 days, and 17% did not become positive until the ninth to eleventh day of incubation.6. The discovery of ehloramphenicol has emphasized the need for the early diagnosis of enteric fever. This can most readily be achieved by the method of blood culture.