Rob, not sure whose current thinking that is -- it's not accurate. Bartonella is contagious -- even from your loved ones. E.g., saliva, sex, etc. as is the case with Lyme disease. Gram negative bacteria are often very good at adapting and even changing forms (phenotypes).
It's funny you say that, as I have cats that I got from rescue shelters. I got Bart from one of them, and here's the proof. My blood draw and microscopy at International Biocare in Tijuana:
https://www.youtube.com/watch?v=qQWggZSS5t4
Try to watch the whole thing. If not, skip to 4:50 to see the Bartonella attaching to my red blood cells.
My other videos are here:
https://www.youtube.com/user/ADRSupport/videos
Hope this helps.