Rapid identification of pathogenic bacteria from clinical positive blood cultures via virus-like magnetic bead enrichment and MALDI-TOF MS profiling

Reducing the time required for the detection of bacteria in blood samples is a critical area of investigation in the field of clinical diagnosis. Positive blood culture samples often require a plate culture stage due to the interference of blood cells and proteins, which can result in significant delays before the isolation of single colonies suitable for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis. In this study, we developed a non-specific enrichment strategy based on SiO₂-encapsulated Fe₃O₄ nanoparticles combined with MALDI-TOF MS for direct identification of bacteria from aqueous environments or positive blood culture samples. Three distinct types of Fe₃O₄@SiO₂ magnetic nanoparticles (MNPs) with unique surface morphologies were developed: spherical MNPs with smooth surfaces (Fe₃O₄@SN), mesoporous silica coated MNPs (Fe₃O₄@MSN), and MNPs exhibiting a viral spiked structure (Fe₃O₄@VSN). These MNPs exhibited excellent binding affinity towards both Staphylococcus aureus and Klebsiella pneumoniae in PBS and artificial saliva solutions. Furthermore, the strategy of using Fe₃O₄@VSN, which involves non-specific interactions between bacterial cells and the virus-like surface, resulted in a dramatic reduction in the minimum detectable concentrations of target pathogens by up to 1000-fold compared to conventional methods. Our results demonstrate that the use of Fe₃O₄@VSN has the potential to significantly reduce the processing time required after blood culture and may be useful for enrichment and identification of microorganisms in complex clinical samples.