Loop-mediated isothermal amplification (LAMP) assay targeting STY2879 gene for rapid detection of Salmonella enterica serovar Typhi in blood

Abstract

Enteric fever is one of the major causes of death and morbidity around the world, especially in resource limited health care facility. The primary reason for empirical therapy in enteric fever management is a lack of rapid diagnostic testing. To improve typhoid fever diagnosis and treatment, as well as to reduce antibiotic overuse, we attempted to develop a loop-mediated isothermal amplification (LAMP) for rapid detection of enteric fever. We designed and evaluated a LAMP assay that targets the STY2879 gene, which is found only in S. Typhi and encodes for reverse transcriptase protein. LAMP utilises three sets of primers to complete the reaction in 60 minutes at 65°C. The LAMP assay procedure in our study for detecting S. Typhi by targeting the STY2879 gene was rapid and more sensitive than the Polymerase Chain Reaction (PCR) method. Among the 107 blood samples that have been tested, the sensitivity and specificity of the assay we obtained were 100% and 87.65% respectively. Also, we demonstrated lower limit of detection (LOD) of target DNA concentration ranging from 10 pg to 5 ng that could be readily detected by a LAMP assay within 60 min. The findings of our study suggest that the LAMP assay is superior to PCR and can be used as a rapid alternative diagnostic tool for the diagnosis of enteric fever in the aspects of specificity and sensitivity. As a result, with some additional enhancements and modifications, this reliable and cost-effective assay can be promptly used to enhance disease management and surveillance.