Dual proximity ligation mediated chain extension and displacement assisted signal cycles for sensitive and accurate methicillin-resistant Staphylococcus aureus (MRSA) detection†

Infectious diseases have emerged as a significant global concern, posing a substantial burden in terms of high morbidity and mortality and presenting considerable challenges in clinical diagnosis and treatment. Therefore, it is highly desired to develop new strategies for sensitive and accurate bacteria detection to address the global epidemic of antibiotic resistance. In this study, a new technique utilizing a dual proximity ligation mediated chain extension and displacement strategy was developed for precise identification and highly sensitive detection of Methicillin-Resistant Staphylococcus aureus (MRSA). The antibodies recognize both protein A and PBP2a on the surface of MRSA, leading to the initiation of proximity ligation and signal amplification processes. The signal amplification procedure generated a substantial number of G-quadruplex sequences, which subsequently bind with thioflavin T (ThT) to significantly amplify its fluorescence, enabling the detection of MRSA with a low detection limit of 3.5 cfu mL⁻¹. In this method, dual proximity ligation assays were integrated to mediate the signal amplification process, thus endowing the method with a greatly elevated specificity in both MRSA identification and signal amplification. Due to its non-label format, high selectivity, and sensitivity, this method can serve as a practical and versatile approach for detecting different bacteria in the early stages of infectious diseases.