How do you prevent brain infection?

Easy: That's a difficult question to answer given brain infections are rare..So to avoid them just live a good healthy life and get regular check-ups.

Healthy living: Bacterial encephalitis is uncommon these days thanks to healthy living and nutrition, getting bad teeth fixed right away, and getting treated promptly for sinusitis or ear infections. Bronchitis, pneumonia, endocarditis etc can spread in the blood stream and need to be treated aggressively to avoid seeding. Viral (herpes, hiv) or fungal brain infections are special situations - ask your doctor.