Detection of Multiple Antibiotic–Resistant Salmonella enterica Serovar Typhimurium DT104 by Phage Replication–Competitive Enzyme-Linked Immunosorbent Assay

A phage replication–competitive enzyme-linked immunosorbent assay (PR-cELISA) was developed for the detection of multiple antibiotic–resistant Salmonella Typhimurium DT104. In the PR-cELISA procedure, a phage, BP1, was inoculated into a log-phase bacterial culture at a ratio of 1:100. After a 3-h incubation of the mixture, BP1 replication was measured by cELISA based on the competitive binding between BP1 and biotinylated BP1 to Salmonella Typhimurium smooth lipopolysaccharide. Among the 84 Salmonella strains and 9 non-Salmonella strains that were tested by PR-cELISA, BP1 detected 39 of 40 Salmonella Typhimurium strains, 2 of 10 Salmonella non-Typhimurium somatic group B strains, and 5 of 18 Salmonella somatic group D₁ strains. With the addition of chloramphenicol to the culture medium, PR-cELISA detected all 27 multiple antibiotic–resistant Salmonella Typhimurium DT104 and none of the other Salmonella strains or non-Salmonella strains tested. The results demonstrated that PR-cELISA has potential applications for the detection of multiple antibiotic–resistant Salmonella Typhimurium DT104.