Transmission Electron Microscopy as a Novel Tool for Diagnostics of Infectious Agents in The Cerebrospinal Fluid

Abstract

Transmission electron microscopy (TEM) remains as an important and irreplaceable tool for direct microbiology diagnostics that allows a fast detection of infectious agents based on visualized morphology. An indisputable advantage this nonselective method is possibility to visualize all present agents in the biological samples in comparison with other techniques that are often highly specific. TEM uses negative contrast electron microscopic techniques where the objects of interests are captured on good film and copper grid coated with a carbon film with is stained by heavy metal salts. This staining surrounds the object and causes dark background, thus it makes the object of interests lighter due to lower ability to disperse primary electrons. By this technique we can visualize 2 nm substructure details. This technique is important not only in viral diagnostics but also in the detection of spirochetes in CSF that may cause several neural symptoms in patients particularly signs of meningoencephalitis. In CSF, we observed both whole spirochetes and their fragments. Importantly the positive diagnostic of the spirochetes can be found even though the serology and PCR methods are negative. To increase the specificity of this technique, we applied an immunoelectron microscopy that uses specific antibodies conjugated with gold particles that binds to the OspA and OspC antigen (Borrelia Burgdorferi). We can often visualize several agents in the CSF sample. Besides spirochetes, several viruses can be present such as Picornavirus or Paramyxovirus. TEM as a nonselective technique for the direct visualization of infectious agents in CSF highly increases the possibility to diagnose the cause of aseptic meningitis.