Phenotypic and Serologic Studies on Salmonella typhi in Patients with Typhoid Fever

Abstract

Diagnosis of typhoid fever is a major issue in Sudan due to the lack of facilities in most microbiological laboratories. The objective of this study was to investigate Salmonella typhi in patients with typhoid fever phenotypically and serologically. Blood and stool specimens were collected from patients suspected to have typhoid fever. Serum was aseptically separated after clot reaction by centrifugation at 3000 rpm for 5 minutes. The serum was used to perform Widal tube method according to standard protocol. Two –fold serial dilutions of serum were prepared in small test tubes with normal saline. 0.05 ml of O antigen was added to each test tube, the same step was repeated for B-O antigen. The tubes were incubated in a water bath at 37 °C overnight. Negative and positive controls were included in each batch of the test. Stool specimens were cultured firstly on Selenite F broth and incubated at 37 °C overnight then sub- cultured on xylose lysine deoxycolate agar plates. The plates were incubated at 37 °C overnight. Biochemical tests were adapted to identify Salmonella typhi . The results revealed that 14 out of 100 tested sera examined were positive (Titre ≥1/160) for typhoid fever. The rest 86 serum specimens were negative (Titre ≤ 1/160). Cultivation of 100 stool specimens reveled that only 4 species of Salmonella typhi and 1 species of Salmonella paratyphi B were identified.‫‪The study concluded that the Widal test remains one of easy‬‬ ‫‪accessible, cheap and simple test but the culture is still remain‬‬ ‫.‪the golden standard method to diagnosis of typhoid fever‬‬