Yes.
Apparently the gut flora rapidly change after childbirth and after gastric bypass.
After childbirth, moving from baby food to permanent adult diet, with severe sickness or surgery including antibiotics; and slowly, if you move to a significantly different environment and eat different foods.
There is also a different and parallel floral environment on the skin, especially in the “coliform zone” from the knees to the navel. It is so unique to the individual that it is thought of as almost a fingerprint. And when people have sex, they get an invasion of a radically different skin flora. This eventually normalizes the flora of a monogamous couple.
However, people who engage in a lot of casual sex can develop a “superflora”, which means that if they have sex with a virgin or someone with a weak immune system, they are likely to give them a “yeast infection” (often mistaken for venereal disease).