Specific detection of Salmonella Typhi by probe-free quantitative polymerase chain reaction

Typhoid fever, predominantly caused by Salmonella Typhi, remains a significant global health concern and hence requires early-stage diagnosis to control the outbreaks of this pathogen. The currently used methods for detecting Salmonella Typhi require more turnaround time, up to 2-3 days, to yield results due to the requirement of bacterial culture and identification. This study represents the robust and specific detection of Salmonella Typhi using quantitative polymerase chain reaction (qPCR) in clinical and biological samples. Here, we describe the development and validation of a qPCR-based approach that enables the direct detection of Salmonella Typhi within 15 h from the time of blood sample collection. Notably, this method eliminates the requirement for genomic DNA isolation and bacterial culture, thus significantly expediting the diagnostic process. The primer set is specific to the gene CdtB of Salmonella Typhi that amplifies a 154-base pair DNA. Through testing over 100 patient samples, we identified five positive cases of Salmonella Typhi infection, with results corroborated by clinical laboratory records. To ensure the specificity and reliability of the qPCR run, all the experiments were performed in triplicate. Remarkably, the developed primer set can distinctly distinguish between the positive and negative samples. This invention holds a promising alternative to the current diagnostic modalities with a specific diagnosis of typhoid fever.