@toni1132 Hi Toni, I soak my showerhead in a plastic container of neat vinegar for at least an hour then screw it back on. The American Thoracic Society suggests using neat bleach. But mycobacteria are resistant to bleach so I don't do that.
The research I've seen shows that mycobacteria grow especially well in showerheads -- much better than in taps etc. (Showerheads can have up to 4,000 times the number of mycobacteria than happens in prdinary running tap water in the same house!). So apart from drinking long-boiled water, very frequent cleaning of our showerheads is the best thing we can do. So I use a cheaper showerhead and replace the whole thing twice a year -- the vinegar causes some rusting around the shower holes.
P.S. Copper showerheads might help to control some bacteria but unfortunately won't help much to kill mycobacteria. The main thing is taking the shower head off and soaking it all in neat vinegar frequently.
Good luck, Annie