Lack of ventilation is a major cause of mould and bacteria developing, so make sure you have an extractor fan that is powerful enough to remove the moisture and humidity from the bathroom and is ducted to the outside.
It’s important to keep your tiles and grout clean. Wiping them down after a shower will help, along with a weekly, more thorough clean.
A regular deep clean by a professional tile and grout cleaner will get rid of anything that your weekly clean can’t reach. They have powerful equipment to extract dirt, grime and bacteria from within the tile and grout, which will reduce the risk of harmful mould setting in and turning into a major problem.