Can you offer any definitive proof of what you say? I have never seen any reliable information anywhere that says anything of the sort. If such were the case one would expect to see all the colloidal silver forums here and elsewhere filled with people complaining about bacterial overgrowths and intestinal problems.
Bacteria multiplies extremely rapidly and it most certainly does NOT take years to regrow beneficial bacteria. It might take years to obtain a healthy BALANCE between the good and bad intestinal flora if you don't take steps to replenish the good bacteria with good probiotics and prebiotics (and that entails far more than popping a few acidiophilus pills or eating a cup or two of store-bought name brand yogurt).
People who fail to do so run the very real risk of the bad bacteria multiplying and dominating, since some bad bacteria multiplies quite rapidly compared to some of the good bacteria. But normally all it takes is plenty of pro and pre-biotics to keep that from happening.
Besides antibiotics, which I do not recommend, there are any number of natural and healthy items which kill off bacteria. It would be nonsense to deprive oneself of all of those items nature has provided, including silver which is itself an essential mineral. A healthy anti-fungal diet such as the Candida diet is good, but I feel sorry for anyone who needlessly suffers through years of strict diets or other regimens without trying what is often a much quicker and more effective solution.