A proof of concept for the detection of enteric bacteria using a multiplex lateral flow immunoassay

Abstract

Background: Enteric bacteria are the inhabitants of the human gut and may cause diarrhoeal disease with high mortality rates in certain communities. The presence of enteric bacteria in faecal matter is confirmed with the gold standard of culture-based assays. Culturing methods are time-consuming, and the bacteria cannot be confirmed rapidly. Hence, molecular assays are becoming the preferred method in developed countries. Polymerase chain reaction (PCR) offers improved and rapid detection; however, postamplification visualisation requires specialised equipment, limiting its use in underdeveloped communities. Considering the need for a simple, rapid, and portable visualisation assay for field use, a lateral flow immunoassay (LFIA) for detecting and confirming amplified genes of Salmonella, Shigella, and Vibrio species was developed.
Methods: Using the agarose gel electrophoresis as a control to LFIA, banked deoxyribonucleic acid (DNA) samples were tested for the presence of Salmonella, Shigella, or Vibrio species genes. The IpaB (Salmonella spp.) targeting the Salmonella pathogenicity islands, IpaH (enteroinvasive Escherichia coli [EIEC]/Shigella spp.) targeting the invasion plasmid antigen H gene of Shigella spp., and EIEC and SodB (Vibrio spp.) targeting the superoxide dismutase genes if present in the samples were amplified with labelled primers and visualised concurrently on agarose gel electrophoresis and LFIA test strips.
Results: The LFIA detected bacterial genes in 33% (44/133) of the samples that displayed positive bands on the agarose gel electrophoresis. No cross-reactivity was detected for enteric strains tested other than Salmonella, EIEC/Shigella, and Vibrio spp. Statistical analysis confirmed a substantial agreement between the test and control methods.
Conclusion: The proof-of-concept LFIA has demonstrated its ability to detect enteric bacterial genetic material and can be optimised as an alternative to agarose gel electrophoresis for the post-PCR amplification detection of pathogens.