&gt; bacteria and human cells are drastically different<p>Doesn&#x27;t that sort of depend on what you consider a human cell?  Our gut bacteria is supposed to be fairly important to us, and something that might affect it on a large scale might have consequences.<p>Note, that I&#x27;m not saying that bacteriophage use if harmful, just that you have to be careful when discounting possible harmful side-effects.  History is rife with examples of new safe health technologies that we only understand the negative aspects of later.