Feasibility of Loop-Mediated Isothermal Amplification for Rapid Detection of Methicillin-Susceptible and Methicillin-Resistant Staphylococcus aureus in Tissue Samples.

Background: To date, few studies have investigated the feasibility of the loop-mediated isothermal amplification (LAMP) assay for identifying pathogens in tissue samples. This study aimed to investigate the feasibility of LAMP for the rapid detection of methicillin-susceptible or methicillin-resistant Staphylococcus aureus (MSSA or MRSA) in tissue samples, using a bead-beating DNA extraction method. Methods: Twenty tissue samples infected with either MSSA (n = 10) or MRSA (n = 10) were obtained from patients who underwent orthopedic surgery for suspected musculoskeletal infection between December 2019 and September 2020. DNA was extracted from the infected tissue samples using the bead-beating method. A multiplex LAMP assay was conducted to identify MSSA and MRSA infections. To recognize the Staphylococcus genus, S. aureus, and methicillin resistance, 3 sets of 6 primers for the 16S ribosomal ribonucleic acid (rRNA) and the femA and mecA genes were used, respectively. The limit of detection and sensitivity (detection rate) of the LAMP assay for diagnosing MSSA and MRSA infection were analyzed. Results: The LAMP result was positive for samples containing 103 colony-forming unit (CFU)/mL for 16S rRNA, 104 CFU/mL for femA, and 105 CFU/mL for mecA. The limits of detection for 16S rRNA and femA were not different between MSSA and MRSA. For the 10 MSSA-positive samples, the LAMP assay showed 100% positive reactions for 16S rRNA and femA and a 100% negative reaction for mecA. For the 10 MRSA-positive samples, the LAMP assay showed 100% positive reactions for 16S rRNA and mecA but only 90% positive reactions for femA. The sensitivity (detection rate) of the LAMP assay for identifying MSSA and MRSA in infected tissue samples was 100% and 90%, respectively. Conclusions: The results of this study suggest that the LAMP assay performed with tissue DNA samples can be a useful diagnostic method for the rapid detection of musculoskeletal infections caused by MSSA and MRSA.