Rapid detection of Salmonella Typhi by loop-mediated isothermal amplification (LAMP) method

Area of Science:

• Microbiology
• Molecular Biology
• Biotechnology

Background:

• Salmonella Typhi (S. Typhi) causes typhoid fever, a significant public health concern, particularly in endemic regions.
• Accurate and rapid detection of S. Typhi is crucial for effective disease management and control.
• Existing diagnostic methods like culture and Polymerase Chain Reaction (PCR) have limitations in terms of speed, sensitivity, or complexity.

Purpose of the Study:

• To establish and evaluate an in-house loop-mediated isothermal amplification (LAMP) assay for the sensitive and specific detection of S. Typhi.
• To assess the performance of the developed LAMP assay against gold standard culture and conventional PCR methods.
• To determine the applicability of the LAMP assay for detecting S. Typhi in field samples.

Main Methods:

• Design of three sets of primers (two outer, four inner) targeting the PapD chaperone gene (locus STBHUCCB_38510) of S. Typhi.
• Optimization of the LAMP reaction using genomic DNA from S. Typhi ATCC7251.
• Visualisation of amplification products via direct colour change (green for positive, orange for negative) and evaluation of specificity, sensitivity, and field sample application.

Main Results:

• The established LAMP reaction demonstrated high specificity and sensitivity for S. Typhi detection.
• The assay showed a colour change for positive (green) and negative (orange) results, allowing for direct visual interpretation.
• Compared to the optimized conventional PCR, the LAMP method was approximately 10 times more sensitive in detecting S. Typhi.

Conclusions:

• The developed in-house LAMP assay is a highly sensitive and specific tool for detecting Salmonella Typhi.
• This method provides a rapid and visually interpretable alternative to conventional diagnostic techniques for S. Typhi.
• The LAMP assay shows potential for effective application in field settings for S. Typhi surveillance and diagnosis.