Colourimetric LAMP assay achieves 100% sensitivity and specificity for field detection of poultry erysipelas

Original abstract

BACKGROUND: Rapid and reliable diagnostic methods suitable for field use are needed for the detection of Erysipelothrix rhusiopathiae in poultry. OBJECTIVES: This study aims to develop and evaluate a colourimetric loop-mediated isothermal amplification (LAMP) assay for the rapid detection of E. rhusiopathiae in conjunction with a rapid DNA extraction procedure suitable for field conditions. METHODS: Specific primers targeting a conserved region of a putative polypeptide gene involved in the synthesis of capsular polysaccharides were used for LAMP and PCR. The specificity of the developed assays was evaluated using 13 unrelated bacterial strains. The efficacy of the assays was assessed using positive controls and 52 clinical samples collected from poultry farms experiencing erysipelas. RESULTS: Both LAMP and PCR showed high sensitivity and specificity when compared with bacterial culture. LAMP and PCR achieved 100% sensitivity and specificity when combined with the rapid DNA extraction method. Using a commercial DNA extraction kit, LAMP maintained 100% sensitivity and specificity, whereas PCR showed 100% sensitivity and 97.8% specificity. The high correlation observed between bacterial culture and the LAMP assay demonstrated the effectiveness and reliability of the rapid DNA extraction method. CONCLUSIONS: The developed colourimetric LAMP assay provides a rapid, sensitive, and practical diagnostic tool for the detection of E. rhusiopathiae in poultry. The assay requires minimal instrumentation, enables straightforward visual interpretation of results, and is suitable for point-of-care testing and resource-limited settings.