When I was in junior high, I ran water that was near boiling down the bell of my cornet about every two weeks. Brass instruments are essentially brazed brass plumbing. Extremely hot water is safe, unless it is an early lacquer. Silver plating is not a problem. I don't do that as often with the trumpets I play now. The best practice is to keep the instrument clean.
Thorough swabbing of the bore after playing and regular treatment with a safe antimicrobial should greatly reduce the risk of such infections. In the case of instruments that have been in storage, a thorough cleaning is in order followed by the same kind of regular maintenance. I am going to look into the idea of camphor crystal packets because this does double duty and reduces key oxidation.
We could all be in fear of shower stall fungus too. The easy answer is keep your shower (and you horn) clean. Typically you'd clean a moldy shower stall before taking a shower. Treat an instrument the same way. Right now I'm testing pure white thyme oil for effectiveness at eliminating mold inside a case that had a musty odor like mildew. The clarinet inside is hard rubber so it should be easy to clean. What I am guessing is that the fumes of the thyme oil will do the trick without the need to saturate the case interior. In this particular experiment the case lining will need to be replaced due to wear. I just want to see if the thyme oil is effective.
Thymol is a chemically processed water soluble version of thyme oil. When I worked in archival document / paper art conservation, we used crystalline thymol to treat documents that displayed foxing (mold). It was very effective just by leaving the documents in a sealed chamber with the crystals for a few days. Natural thyme oil has the same properties but has to be carried in an oil. Thyme oil mixed into the bore oil seems to make a lot of sense to me. Beware of the chemically processed thymol crystals. Thymol is mildly carcinogenic. The natural thyme oil is not.
Saxophones? "How many saxophone players does it take to clean the shower......"
There are areas in a sax, particularly the goose necks of the tenor and baritone that are not swab friendly. If there are corks and pads on those, or steel sprung mechanisms you can't really dunk them in steaming water like I do with my trumpets and cornets and other valved brass. Likewise, you can't spike a bore oil with thyme and tea tree. An alcohol soaked swab might be in order for those goose necks. Bassoon bocals have the same problem and thin silk swab is used to dry them out and clean them.
The other side of it is keeping your immune system healthy. That might be primary. Most of these infections are opportunist microbes that can't get a toe hold in a healthy individual. Eat clean, drink clean, live clean and you are more likely to stay clean.