Fluorescent Detection of Methicillin Resistant Staphylococcus aureus by Loop-mediated Isothermal Amplification Assisted with Streptavidin-coated Quantum Dots

Background: Methicillin Resistance Staphylococcus aureus (MRSA) could be considered as a major concern in medicine can cause nosocomial infec-tion and bacteremia, especially in patients using catheter and household medical devices. Methods: Using molecular diagnostic methods are important for identifica-tion of MRSA from the Methicillin Sensitive Staphylococcus aureus (MSSA). Here we described a fluorescent assay using biotin-labelling Loop-medi-ated isothermal amplification (LAMP) method assisted with streptavidin-coated Quantum Dots (QDs) for detection of MRSA. For comparison, an-other fluorescent assay using LAMP assisted with Green Viewer (GV; a fluorescent dye) was applied for detection of MRSA. The mecA gene was selected as the target for amplification by LAMP and for biotin-labeling of the LAMP amplicons, biotin-11-dUTP was mixed with the dNTPs (deoxy Nucleotide Phosphates) in LAMP reaction. For determining the clinical performance of the developed assay, 30 blood samples with MRSA posi-tive results were tested with QD-LAMP, the conventional LAMP, GV-LAMP, and Polymerase Chain Reaction (PCR). Results: Obtained results indicated that % sensitivity of QD-LAMP was 86.66% for detection of mecA positive MRSA samples; however, the Limit of Detection (LoD) of QD-LAMP was 1.5×104 Colony Forming Unit (CFU). Conclusion: The results suggested that the QD-LAMP assay was easy to operate and could be used for detection of MRSA in parallel to the blood culture with less sensitivity for detection of bacteremia and pediatric septi-cemia with low counts of MRSA.