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Open Access Research article

Bacteria tracking by in vivo magnetic resonance imaging

Verena Hoerr1, Lorena Tuchscherr2, Jana Hüve35, Nadine Nippe4, Karin Loser4, Nataliya Glyvuk5, Yaroslav Tsytsyura5, Michael Holtkamp6, Cord Sunderkötter4, Uwe Karst6, Jürgen Klingauf35, Georg Peters2, Bettina Löffler2 and Cornelius Faber1*

Author affiliations

1 Department of Clinical Radiology, University Hospital Münster, Münster 48149, Germany

2 Institute of Medical Microbiology, University Hospital Münster, Münster 48149, Germany

3 Fluorescence Microscopy Facility Münster, Institute of Medical Physics and Biophysics, University Hospital Münster, Münster 48149, Germany

4 Department of Dermatology, University Hospital Münster, Münster 48149, Germany

5 Institute of Medical Physics and Biophysics, University Hospital Münster, Münster 48149, Germany

6 Institute of Inorganic and Analytical Chemistry, University of Münster, Münster 48149, Germany

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Citation and License

BMC Biology 2013, 11:63  doi:10.1186/1741-7007-11-63

Published: 28 May 2013

Abstract

Background

Different 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.

Results

We 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.

Conclusion

Labeled 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.

Keywords:
Bacterial cell labeling; Bacteria tracking; Infectious diseases; Mouse models of infection; Cellular and molecular MRI