Bacteria tracking by in vivomagnetic resonance imaging

Abstract

BackgroundDifferent non-invasive real-time imaging techniques have been developed over the last decades to study bacterial pathogenic mechanisms in mouse models by following infections over a time course. In vivo investigations of bacterial infections previously relied mostly on bioluminescence imaging (BLI), which is able to localize metabolically active bacteria, but provides no data on the status of the involved organs in the infected host organism. In this study we established an in vivo imaging platform by magnetic resonance imaging (MRI) for tracking bacteria in mouse models of infection to study infection biology of clinically relevant bacteria.ResultsWe have developed a method to label Gram-positive and Gram-negative bacteria with iron oxide nano particles and detected and pursued these with MRI. The key step for successful labeling was to manipulate the bacterial surface charge by producing electro-competent cells enabling charge interactions between the iron particles and the cell wall. Different particle sizes and coatings were tested for their ability to attach to the cell wall and possible labeling mechanisms were elaborated by comparing Gram-positive and -negative bacterial characteristics. With 5-nm citrate-coated particles an iron load of 0.015 ± 0.002 pg Fe/bacterial cell was achieved for Staphylococcus aureus. In both a subcutaneous and a systemic infection model induced by iron-labeled S. aureus bacteria, high resolution MR images allowed for bacterial tracking and provided information on the morphology of organs and the inflammatory response.ConclusionLabeled with iron oxide particles, in vivo detection of small S. aureus colonies in infection models is feasible by MRI and provides a versatile tool to follow bacterial infections in vivo. The established cell labeling strategy can easily be transferred to other bacterial species and thus provides a conceptual advance in the field of molecular MRI.

MRI Visualization of Staphyloccocus aureus-Induced Infective Endocarditis in Mice

“…S. aureus can be labeled with iron oxide nano particles in vitro and applied for induction of infections in mice. Vegetations in these models are readily observable in T2* weighted MRI, as previously shown in subcutaneous or semi-systemic infection models [21]. In the present work, we have developed a mouse model of S. aureus -induced IE and combined the CINE UTE MRI of the valves with iron-labeling of S. aureus , to assess whether MRI can detect IE.…”

Complexes of Metal-Based Nanoparticles with Chitosan Suppressing the Risk of Staphylococcus aureus and Escherichia coli Infections

“…Recently, magnetic nanoparticles (MNPs) were also considered as contrast agents for MRI because they take advantage of property changes that occur when materials are nano-scaled (Cormode et al, 2013). In vivo investigations of bacterial infections previously relied mostly on bioluminescence imaging; however, in vivo bacteria tracking (Hoerr et al, 2013) or monitoring of progress of bacterial diseases (Ali et al, 2014) by MRI has been utilized. The fluorescence microscopy and flow cytometry are based on fluorescence marks utilizing externally added fluorophores that selectively bind to specific targets in tissues.…”

In vivo targeted peripheral nerve imaging with a nerve-specific nanoscale magnetic resonance probe

“…The relationship of these was expressed as the SNR, and a high SNR image is desirable for MRI. With recent developments in hardware and sequences, high-field MRI and dedicated animal scanners have been able to image at the single-cell resolution while still maintaining an ideal SNR [36][37][38]. Therefore, we hypothesized that in vivo targets of peripheral nerve-specific proteins, specifically, myelin-associated proteins, could be imaged using MCMRI and its specific MRI probes accompanied by optimal MRI techniques and a high-field scanner.…”