ScienceDaily (June 24, 2008) — Microbiologists at the University of Calgary have demonstrated the first direct visualization of the dissemination of Borrelia burgdorferi, the bacterium that causes Lyme disease. This real-time, three-dimensional look at spirochete dissemination in a living mammalian host.

Pathogenic spirochetes are a group of bacteria that cause a number of emerging and re-emerging diseases worldwide, including syphilis, leptospirosis, relapsing fever, and Lyme disease. The mechanism by which they disseminate from the blood to target sites is unknown. Direct visualization of these bacteria may yield critical insight into resultant disease processes.

The team therefore set out to directly observe these bacteria at the single-cell level in a living host, using an engineered fluorescent strain of B. burgdorferi as an example bacterium. Using conventional and spinning disk confocal microscopy, the investigators were able to track the movement of the bacteria and the interaction of the bacteria with the vascular wall in mice. They found that vascular escape is a multi-stage process and that spirochete movement appears to play an integral role in dissemination from the blood to target tissue sites.

This use of high-resolution, 3D imaging to visualize the dissemination of a bacterial pathogen in vivo lays the groundwork for a better understanding of the mechanisms by which these and other bacteria disseminate throughout the body to cause disease.

Journal reference:

1. Moriarty TJ, Norman MU, Colarusso P, Bankhead T, Kubes P, et al. Real-Time High Resolution 3D Imaging of the Lyme Disease Spirochete Adhering to and Escaping from the Vasculature of a Living Host. PLoS Pathog, 4(6): e1000090 DOI: 10.1371/journal.ppat.1000090

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B) Phase contrast and epifluorescent visualization of spirochetes cultured from mouse ears. Ear punches obtained from infected C3H/HeN mice 13 days after inoculation were cultured in BSK-II medium in the absence of gentamycin selection before visualization. C) Visualization of live fluorescent B. burgdorferi in a living mouse ear by spinning disk confocal IVM. The spirochetes, indicated by yellow arrows, were observed four weeks after intraperitoneal inoculation of a C57 BL/6 mouse. Blood vessels were visualized by jugular vein injection of FITC-labeled albumin. Video footage of fluorescent B. burgdorferi moving in the ear of a living C57 mouse is presented in Video S1. (Credit: Moriarty et al., PLoS Pathog, 4(6): e1000090 DOI: 10.1371/journal.ppat.1000090)

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