|RMJ. 2017; 42(4): 475-478
Detection of Salmonella enterica serover Typhi from Widal-positive blood specimens by blood culture and PCR targeting aroC and fliC genesSafiullah Khan Achakzai, Zafar Ahmed, Abdul Samad, Muhammad Naeem, Hamida, Muhammad Ali, Muhammad Rizwan, Farah Sabeen Bugti, Sania Ashraf, Muhammad Tayyeb, Olena Pokryshko.
Objective: The study aimed at investigating the validity of multiplex-PCR for S. typhi detection in blood specimens of Widal-positive typhoid patients and to compare the detection rate of PCR with blood culture.
Methodology: Blood specimens were collected from 105 clinically suspected and Widal- positive typhoid patients. For the bacterial culture, the specimens were inoculated into Brain Heart Infusion (BHI) broth. The growth was subcultured on Xylose Lysine Deoxycholate (XLD) and Salmonella-Shigella (SS) agar. Obtained colonies were Gram-stained and subjected to biochemical tests. Multiplex-PCR was performed to amplify a 639-bp fragment of aroC gene specific for Salmonella and a 495-bp fragment of fliC gene for S. typhi.
Results: Of 105 Widal-positive typhoid patients, 73 (69.6%) were positive by PCR for the presence of S. typhi and 24 (22.8%) by blood culture. PCR could also amplify S. typhi DNA from 49 (46.7%) culture-negative patients. Widal test with false-positive result was observed in 32 (30.4%) suspected cases.
Conclusion: Our study suggests that PCR-based diagnosis of typhoid fever is distinctly useful in culture-negative cases and also false-positive cases as detected by Widal test.
Key words: Salmonella typhi, diagnosis, Widal test, blood culture, PCR