A rapid loop-mediated isothermal amplification (LAMP) method for detection of the macrolide–streptogramin type B resistance gene msrA in Staphylococcus aureus

• Staphylococcus aureus isolates carrying msrA gene have a multidrug resistance phenotype.
• A rapid assay to detect msrA by loop-mediated isothermal amplification (LAMP) was developed.
• This assay might allow monitoring of multidrug-resistant strains.

Macrolide–streptogramin type B resistance (the MSB phenotype) is a multidrug resistance phenotype in Staphylococcus aureus conferred by the resistance gene msrA. However, bacteria having the MSB phenotype are susceptible to lincosamides and 16-membered ring macrolides, which makes profiling resistance genes necessary and urgent for timely and appropriate use of antimicrobials. In this study, the loop-mediated isothermal amplification (LAMP) assay was optimized for prompt detection of the msrA gene. msrA gene sequences were obtained from the National Center for Biotechnology Information (NCBI) database and primers were designed using the LAMP primer designing software PrimerExplorer v.4, which together recognize seven distinct regions of the msrA gene. The specific LAMP primer set designed in this study could amplify the msrA gene within 25 min at an isothermal temperature of 62 °C. More importantly, the msrA gene could be detected at a sensitivity as low as 100 pg. Furthermore, this optimized LAMP assay provided swift detection of the msrA gene even directly from human specimens. In conclusion, this assay may have great clinical application potential for detection of the msrA gene.