Hello from JustAnswer.
A bacterial culture growing a significant amount of E. coli may not be an overgrowth of the E. coli. E. coli is one of the normal germs in the colon. And the colon serves as a reservoir for E. coli to cause infections elsewhere in the body, such as in the urinary tract.
If one normal germ is growing disproportionately to the other germs that also typically grow in the stool, it may be an overgrowth of the one germ or it may be due to the loss of other germs. If there is a loss of the normal competition between germs because of the absence of certain germs, then whichever germ remains will grow more than usual.
Simply taking antibiotics may make the problem worse, as it may interfere with the return of the competing bacteria. Taking probiotics, such as you have been doing, is reasonable, but there are also several different types of probiotics, depending upon which germs are present, and it may be more effective to alternate between different probiotics.
The other issue that can arise and cause the symptoms that you describe is excessive growth of a germ in a portion of the gut that is not supposed to have much growth of the germ, such as in the small intestine, called SIBO (for small intestinal bacterial overgrowth). Finding and diagnosing SIBO can be difficult and may require specialized testing by a Gastroenterologist.
So, if you have only tried one type probiotic, it would be reasonable to first try several types of probiotics. If that is ineffective, then it would be better to first see a Gastroenterologist before simply taking an antibiotic for the E. coli.
If I can provide any additional information, please let me know.