Selective Capture and Identification of Methicillin-Resistant Staphylococcus aureus by Combining Aptamer-Modified Magnetic Nanoparticles and Mass Spectrometry

Abstract

A nucleic acid aptamer that specifically recognizes methicillin-resistant Staphylococcus aureus (MRSA) has been immobilized on magnetic nanoparticles to capture the target bacteria prior to mass spectrometry analysis. After the MRSA species were captured, they were further eluted from the nanoparticles and identified using matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). The combination of aptamer-based capture/enrichment and MS analysis of microorganisms took advantage of the selectivity of both techniques and should enhance the accuracy of MRSA identification. The capture and elution efficiencies for MRSA were optimized by examining factors such as incubation time, temperature, and elution solvents. The aptamer-modified magnetic nanoparticles showed a capture rate of more than 90% under the optimized condition, whereas the capture rates were less than 11% for non-target bacteria. The as-prepared nanoparticles exhibited only a 5% decrease in the capture rate and a 9% decrease in the elution rate after 10 successive cycles of utilization. Most importantly, the aptamer-modified nanoparticles revealed an excellent selectivity towards MRSA in bacterial mixtures. The capture of MRSA at a concentration of 102 CFU/mL remained at a good percentage of 82% even when the other two species were at 104 times higher concentration (106 CFU/mL). Further, the eluted MRSA bacteria were successfully identified using MALDI mass spectrometry.

Aptamers: A prospective tool for infectious diseases diagnosis

“…Furthermore, to detect SEs, scientists have also developed aptamer C10 for S. aureus enterotoxin C1 (SEC1), aptamer R12.06 for □toxin, aptamer Antibac1 and Antibac2 for a peptidoglycan, and aptamer PA#2/8 for protein A. [54][55][56][57] Methicillin-resistant Staphylococcus aureus (MRSA), usually referred to as "superbug", is a nosocomial and multi-drug resistant microbe presenting tolerance to β-lactam antimicrobials. 53 Currently, substantial traditional approaches have been proposed…”

“…Those approaches have some limitations in the identification of MRSA, e.g., cultivationrelated approaches are fairly low efficient. 54 In the face of the worldwide crisis of antibiotic resistance, there is an urgent need has been extended from the nucleic acid identification to microbe identification. 56 The results show that their method has significantly improved sensitivity in the detection of MRSA.…”

“…Cultivation‐related approaches, like the disk diffusion test and microdilution approach, mainly depend on the suppressive content of antimicrobials, while DNA‐derived approaches, like PCR, target the mecA gene. Those approaches have some limitations in the identification of MRSA, e.g., cultivation‐related approaches are fairly low efficient 54 . In the face of the worldwide crisis of antibiotic resistance, there is an urgent need for new high‐specificity and high‐sensitivity bacterial detection strategies.…”

“…Furthermore, to detect SEs, scientists have also developed aptamer C10 for S. aureus enterotoxin C1 (SEC1), aptamer R12.06 for □‐toxin, aptamer Antibac1 and Antibac2 for a peptidoglycan, and aptamer PA#2/8 for protein A. 54 , 55 , 56 , 57 …”

“…Those approaches have some limitations in the identification of MRSA, e.g., cultivation‐related approaches are fairly low efficient. 54 In the face of the worldwide crisis of antibiotic resistance, there is an urgent need for new high‐specificity and high‐sensitivity bacterial detection strategies. Clinically, the accurate and rapid identification of MRSA is pivotal.…”