Fiber optic microendoscopy for preclinical study of bacterial infection dynamics

Citation

Mufti, N., Kong, Y., Cirillo, J. D., & Maitland, K. C. (2011). Fiber optic microendoscopy for preclinical study of bacterial infection dynamics. Biomedical Optics Express, 2(5), 1121–1134.

Keywords

• Fiber optic microendoscopy
• Bacterial infection
• Mycobacterium bovis Bacillus Calmette-Guérin (BCG)
• tdTomato
• In vivo imaging
• Subcutaneous infection
• Intra-tracheal infection
• Detection limit
• Fluorescence
• Confocal microscopy

Brief

Researchers developed and characterized a fiber optic microendoscope that can detect bacterial lung and skin infections in mice, showing promise for improved in vivo imaging of bacterial infections.

Summary

This article presents a fluorescence microendoscope and explores its potential for imaging and quantifying bacterial infections.

Here are the key findings from the study:

• A fluorescence microendoscope, with a resolution of 4 µm and a 750 µm field-of-view, was developed to visualize bacteria in vivo. This device utilizes a fiber optic bundle to excite fluorescently labeled bacteria and collect the emitted signal.
• The system successfully detected and resolved:

1. Bacterial colonies in vitro.
2. Regions of bacterial infection in the skin and lungs of mice.
3. Subcutaneous inoculations of bacteria at concentrations ranging from 10⁶ to 10⁴ CFU (colony forming units).
4. Intra-tracheal inoculations of bacteria ranging from 10⁸ to 10⁶ CFU.

• The average fluorescence signal from bacteria in the skin and lung images demonstrated a linear relationship with CFU. This correlation suggests the potential for using this system to quantify bacterial load in vivo.
• The system's limit of detection was determined to be:

1. 10⁴ CFU for subcutaneous inoculations in the skin.
2. 10⁷ CFU for intra-tracheal inoculations in the lungs.

However, the authors note:

• Bacteria may be detectable at lower concentrations, but detection may be obscured by tissue autofluorescence or limitations in image analysis techniques.
• The microendoscope demonstrates promise for in vivo imaging using a smaller fiber bundle that could be delivered directly into the lungs via a catheter. This approach could facilitate the study of bacterial infections, such as tuberculosis, in their native environment.
• The microendoscope, with modifications, could enable dual-channel imaging. This advancement would allow for simultaneously visualizing bacteria and host cells, providing insights into the dynamics of infection.

The authors conclude that this microendoscope has the potential to enhance our understanding of bacterial infection progression and facilitate the development of improved diagnostic and therapeutic strategies.

Origin: https://opg.optica.org/boe/fulltext.cfm?uri=boe-2-5-1121&id=211652