Development of a LAMP assay for rapid detection of different intimin variants of attaching and effacing microbial pathogens

Intimin harboured by pathogenic Escherichia coli (E. coli) strains is a key virulence factor involved in host cell adherence and colonization. Twenty-seven intimin-encoding E. coli attaching and effacing (eae) gene variants have been reported according to their 3' binding domain sequences. In our study, we developed a specific and sensitive loop-mediated isothermal amplification (LAMP) assay to detect all known intimin variants. Four primers specific for six regions of eae genes were designed using online software. The eae-LAMP assay was highly specific and detected all 27 tested eae variants; no cross-reactions were observed with genes from enterotoxigenic E. coli (ETEC), E. coli BL21, Salmonella, Shigella, Listeria monocytogenes, or Streptococcus suis type 2 (SS2). With the lowest detection limit of approximately 10 copies per reaction the eae-LAMP assay was 100 times more sensitive than conventional PCR. These results, and the results of tests involving food and faecal samples artificially contaminated with E. coli O157 : H7 (eaeγ+), show that the eae-LAMP assay is a simple, rapid, sensitive and specific tool for detecting intimin variants from pathogenic strains of E. coli. The eae-LAMP assay has great potential for wider applications, not only in the laboratory but also in the field setting, as it does not require specialized equipment.