There are a lot of things that we can't control when it comes to our gut health. If we are sick, and the GP suggests antibiotics, then it is something we can't avoid. Don't take antibiotics unless absolutely necessary. It saves the healthy gut bacteria from being wiped out and causing long term changes to your gut microbiota.
Eating a healthy diet is also key to good intestinal health. Studies have shown that eating a typical western diet that is low in fibre and high in processed foods has been linked with alteration in gut microbiota and increased chronic disease risk (inflammatory bowel disease anyone!) A diet consisting of variations of plant foods are necessary to have a variety of strains of good bacteria in the gut. Diversity is key to a healthy gut.