The rapid and visual detection of methicillin-susceptible and methicillin-resistant Staphylococcus aureus using multiplex loop-mediated isothermal amplification linked to a nanoparticle-based lateral flow biosensor.

Background: Staphylococcus aureus (S. aureus), including methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA), is an eminent human pathogen that can colonize the human host and cause severe life-threatening infections. The development of a reliable, simple and rapid assay for detecting S. aureus and identifying MRSA is important for diagnosis and follow-up treatment.

Methods: A novel molecular diagnosis technique, named multiplex loop-mediated isothermal amplification linked to a nanoparticle-based lateral flow biosensor (m-LAMP-LFB), was applied to detect all S. aureus species and identify MRSA. Two sets of primers were designed based on the femA gene (S. aureus-specific gene) and the mecA gene (encoding penicillin-binding protein 2a), and the multiple-LAMP products were analyzed using LFB. The m-LAMP-LFB amplification conditions, including the target DNA concentration, reaction temperature and time, were optimized. The sensitivity and specificity of the m-LAMP-LFB method were tested in the current study, and the multiple-LAMP-LFB technology was applied to detect the MSSA and MRSA strains from clinical samples.

Results: The S. aureus- and MRSA-specific primers based on the femA and mecA genes allowed the multiple-LAMP technology to detect S. aureus and MRSA, respectively. The multiple-LAMP conditions were optimized at 63 °C for 40 min. The full process, including genomic DNA template preparation, LAMP, and product identification, could be achieved in 80 min. The limit of detection (LoD) of the multiple-LAMP assay for femA and mecA detection was 100 fg of genomic DNA template per reaction. The specificity of m-LAMP-LFB detection was 100 %, and no cross-reactions to non-S. aureus strains were observed.

Conclusion: The multiple-LAMP-LFB technique developed in the current study is a reliable, simple, rapid, specific and sensitive method to identify MSSA and MRSA infections for appropriate antibiotic therapy.