ABSTRACT
The present study developed a loop-mediated isothermal amplification (LAMP) assay that amplifies the fragments of O4 Salmonella enterica-specific gene rfbJ and evaluates the potential use in detection of Salmonella enterica serovar Typhimurium (ST). The detection limit of the LAMP assay was 10(3) CFU/ml, which was lower than that of the PCR assay with the same target gene (10(5) CFU/ml), confirmed by electrophoresis. The increased turbidity of the final products of LAMP was also observed with more than 10(3) CFU/ml. Furthermore, the LAMP assay took only 60 min for a reaction, while the PCR assay needed 80-90 min for a reaction and approximately 30 min for the subsequent electrophoresis to confirm the specific band. The positive reaction was only observed for 55 strains of 11 serovars of O4 group Salmonella enterica. The LAMP assay developed in the present study is considered to be an effective method for specific detection of the O4 group Salmonella enterica serovars, including ST.
Subject(s)
Nucleic Acid Amplification Techniques/methods , Salmonella enterica/classification , Salmonella enterica/isolation & purification , Bacteriological Techniques , Base Sequence , DNA, Bacterial , Genes, Bacterial , Molecular Sequence Data , Polymerase Chain Reaction , Sensitivity and Specificity , Time FactorsABSTRACT
In the present study, the loop-mediated isothermal amplification (LAMP) assay was developed to amplify the fragments of the O9 Salmonella-specific insertion element and evaluated in the laboratory for its potential use in a field situation, such as poultry farms. Among the bacteria tested, a positive reaction was observed only for 128 strains of 6 serovars of the O9 group Salmonella, such as Enteritidis (SE) and Pullorum. The detection limit of the LAMP assay was 10(3)CFU/ml, which was more sensitive than that of the polymerase chain reaction (PCR) assay with the same target gene (10(6)CFU/ml). The final results were obtained within 30 min for the LAMP assay, while the PCR assay needed a total of 120 min. When the LAMP assay was applied to the enrichment broth mixed with cecal dropping samples either spiked with SE in vitro or excreted by SE-inoculated hens, the results were comparable to those of the conventional plating method including 2 separate enrichments. In conclusion, the LAMP assay developed in the present study is an effective method for the specific detection of the O9 group Salmonella serovars, including SE.
