@Antares in NYC , I will give it a go.
A chimera is an organism that contains DNA from two otherwise discreet organisms. You can have chimeric plants, and chimeric animals. On a cellular level, a chimera is the result of genetically different or unique cells; it is like an independent hybrid of two organisms.
I think what MacDonald is claiming is that he has found via staining, in plaques within donated Alzheimer's brains, biofilms that are comprised in part, not just of Lyme or B Miyamotoi, but a genetic crossbreed of the two. A spirochetal chimera. He also found distinct and viable Bb and miyamotoi in these plaques, findings which are equally significant for different reasons...But the chimera carries implications that resonate back in time to undermine many claims made by mainstream Lyme.
Antibody tests for Lyme and for B Miyamotoi (theoretically since there aren't yet commercially available tests for miyamotoi), are based on identifying outer surface proteins of the spirochetes. But the chimeric affect confounds that process by reshuffling the protein deck in such a way as to render current Borrelia metrics useless. As MacDonald notes, "Chimera DNA produces chimera proteins."
He also addresses his theory about Borrelia contributing to Alzheimer's. Judith Miklossy out of Switzerland (I think) has also addressed the role of different spirochetes, including Borrelia, in degenerative dementias. One aspect I found fascinating was his theory that amyloid deposits are DEFENSE mechanisms against the chimera filled brain biofilms. He is postulating that the infamous amyloid plaques associated with Alzheimers are biofilms - biofilms covered in amyloid.
These findings will need to be verified, of course, and I don't think anyone should assume that that will happen soon, if at all. We have a history, both within Lyme and ME/CFS communities, of exciting developments that fall stillborn for one reason or another.
We can already anticipate some of the responses: Geographically, Bb dispersion does not map to Alzheimers or MS etc. Or an independent team will dissect a group of Alzheimers' brain and find no evidence of biofilms of any kind of Borrelia.
They may be proven right. We will have to wait and see.
It would be nice, though, if I could read of independent verification efforts, and not have to wonder how and when "independent" lost its way.