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Bacterial Infection on the ASK


Overview


Preclinical tools are necessary to study bacterial infection as it is both a costly and serious clinical issue. Terminal collection of infected tissue for histology or culture is a standard method of determining the progression of bacterial infection. While effective, the approach is invasive and time consuming. In vivo imaging using fluorescent agents is an attractive alternative as it allows for rapid and non-invasive determination of disease progression and treatment efficacy. Optical in vivo imaging technology has been successfully used to non-invasively measure the spread of infection, monitor infection dynamics and determine the in vivo efficacy of antimicrobial compounds in various infectious disease models can be monitored and tracked non-invasively in living animals using one of PerkinElmer’s IVIS or FMT Imaging Systems.


Products for imaging bacterial infection


The following agents can be used to study infectious disease in vivo. In many cases these agents can also be used for in vitro and ex vivo applications. More information on each agent, such as technical information, protocols for use, and ordering information can be found by clicking on the links below. 
  • BacteriSense targets the negative charge on the surface of bacterial membranes. This probe has a short blood half-life allowing for re-injection every 24 hours to monitor infectious disease models. The 645 emission wavelength of this probe makes it possible for fluorescent microscopy visualization using commonly available microscopy filters.
  • RediJect Bacterial Detection Probe 750 also binds to the negatively charged surface of bacteria, however this agent has a longer blood half-life (18 hours) compared to BacteriSense 645, allowing for longer post-injection imaging time points.
  • Optical Reporter Microorganisms are bioluminescent Gram-positive and Gram-negative bacterial strains validated in vitro and in vivo. They can be used alone, or in combination with our fluorescent agents to monitor bacterial infections and the efficacy of drug treatments. Also available are bioluminescent plasmids which can be transfected into your bacterial cell line of interest. 

The agents above specifically detect bacteria at the site of infection, for products which can be used to detect inflammation associated with infectious disease please visit the Acute Inflammation or Pulmonary Inflammation sections for more information on these applications.


Mouse models of infection


In the infectious disease model below, bacterial infection is detected using a near-infrared fluorescent agent which binds to anionic lipids within the bacterial membrane. Agent can be injected 18-24 hours post bacterial injection, and fluorescence monitored as early as 1 hour post injection (if using BacteriSense™ 645) or later time points (if using Bacterial Detection Probe 750 which has a much longer half-life).

Bacteria are injected into the mouse. Some 18-24 hours later, NIR bacterial imaging agent is injected retro-orbitally. If using BacteriSense 645, the mouse is imaged 1 hour post agent injection while if using Bacterial Detection Probe 750, 18-24 hours post agent injection the animal can be imaged. Both probes can be used to monitor infection treatment efficacy in realistic timeframes and can be imaged on either FMT or IVIS imaging systems. Agents can be imaged in three dimensions or planarly. While 2D planar imaging allows for optical monitoring of infection, 3D tomography allows the added advantage of quantifying concentration of dye at the site of infection.

bacterialinfectionfig1.jpg
Figure 1: Schema of the infection model.

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Figure 2: Sensitivity of Detection using BacteriSense 645. 105 to 108 colony forming units (CFU) of E. coli were injected intramuscularly in the left flank of the mouse, 18 hours later BacteriSense 645 was injected intravenously and mice were imaged 1 hour post-agent injection. Tomography and planar 2D images generated using FMT2500. The color bar represents either fluorescent concentration in nM (tomography) or fluorescent brightness in counts/energy (2D planar).

In Figure 3 below, Optical reporter microorganisms are used to initiate infection, which can be tracked using a bioluminescent imager (such as the IVIS® Spectrum).

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Figure 3: Pneumonia model in mice using Bacterial Detection Probe and S. pneumonia strain Xen10. In vivo fluorescence imaging at depth in pneumonia. Nu/nu mice were infected with S. pneumoniae strain Xen10 intranasally and infection in the lungs was monitored with bioluminescence imaging (A). 3D reconstructed BLI image was co-registered with micro CT using the Quantum FX micro CT system (B). RediJect Bacterial Detection Probe was administered intravenously and mice were imaged using the transillumination (Trans-Raster 745/800) feature of the IVIS Spectrum. The probe targeting the lung infection can be clearly monitored non-invasively (C).


Application notes and posters



Citations


Please visit our Citations Library for references using our pre-clinical imaging agents for infectious disease studies.