Identification of Five NovelSalmonellaTyphi-Specific Genes as Markers for Diagnosis of Typhoid Fever Using Single-Gene Target PCR Assays

Abstract

SalmonellaTyphi (S. Typhi) causes typhoid fever which is a disease characterised by high mortality and morbidity worldwide. In order to curtail the transmission of this highly infectious disease, identification of new markers that can detect the pathogen is needed for development of sensitive and specific diagnostic tests. In this study, genomic comparison ofS. Typhi with other enteric pathogens was performed, and 6S. Typhi genes, that is, STY0201, STY0307, STY0322, STY0326, STY2020, and STY2021, were found to be specificin silico. Six PCR assays each targeting a unique gene were developed to test the specificity of these genesin vitro. The diagnostic sensitivities and specificities of each assay were determined using 39S. Typhi, 62 non-TyphiSalmonella, and 10 non-Salmonellaclinical isolates. The results showed that 5 of these genes, that is, STY0307, STY0322, STY0326, STY2020, and STY2021, demonstrated 100% sensitivity (39/39) and 100% specificity (0/72). The detection limit of the 5 PCR assays was 32 pg for STY0322, 6.4 pg for STY0326, STY2020, and STY2021, and 1.28 pg for STY0307. In conclusion, 5 PCR assays using STY0307, STY0322, STY0326, STY2020, and STY2021 were developed and found to be highly specific at single-gene target resolution for diagnosis of typhoid fever.