Comment by gadders
I read this article once: https://www.newyorker.com/magazine/2015/12/07/bacteria-on-th...
" The tumor had spread to his brain stem and was shortly expected to kill him. Muizelaar cut out as much of the tumor as possible. But before he replaced the “bone flap”—the section of skull that is removed to allow access to the brain—he soaked it for an hour in a solution teeming with Enterobacter aerogenes, a common fecal bacterium. Then he reattached it to Egan’s skull, using tiny metal plates and screws. Muizelaar hoped that inside Egan’s brain an infection was brewing."
The scientists did get penalised for it but as a hail mary it might be worth investigating. My best wishes for your friend.