Multiplex PCR for Diagnosis of Salmonella enterica Serovar Typhi

Background: Typhoid fever caused by Salmonella enterica serovar Typhi is endemic in developing countries. Its detection by culturing on specific media or serological methods like the Widal test is time consuming and/or less sensitive than the PCR technique. Here we apply a multiplex PCR dependent detection for S. Typhi using two specific primers for invA and fliC genes. Methods: 76 patients with clinical suspicion of typhoid fever were examined. Two sets of primers derived from invA and fliC genes specific for Salmonella spp. and S. Typhi were used as multiplex PCR in order to detect the pathogen in their blood samples. This was compared with traditional culturing methods on two different chromogenic media [Melibiose, mannitol, and sorbitol (MMS) agar media specific for S. Typhi and Salmonella-Shigella (SS) agar media]. Also, the suspected typhoid samples were tested by Widal 0 antigen. Results: The sensitivities of culturing, Widal test, and multiplex PCR were 61.36%, 88.64%, and 100%, respectively, while their specificities were 100%, 62.50%, and 86.49%, respectively. The multiplex PCR showed higher efficiency reaching 93.42% compared to culturing and Widal test which was 77.63%. Conclusions: The high sensitivity, specificity, and efficiency of the studied multiplex PCR encourage us to recommend it as a useful tool for S. Typhi detection not only in clinically suspected negative culture individuals, but also for the false positive Widal test cases of typhoid fever in endemic regions.