> But doctors at Great Ormond Street Hospital attempted an untested "phage therapy", which uses viruses to infect and kill bacteria. Phage-therapy never became mainstream medicine and the field was eclipsed by the discovery of antibiotics, which are much easier to use.

Yes, phage therapy quickly disappeared after antibiotics were discovered. At the time, antibiotics were more convenient as they usually help against a wide range of bacteria while with phages you need to specifically test which phage works best for the strand you want to fight. It takes days with phages vs minutes with antibiotics.

The co-discoverer of phages went to georgia and helped establish phage research at a medical institue [1]. The institute survived through the horrible times of stalin and later it became of strategic importance as the west didn't share antibiotics with the soviet union. Due to the strategic importance, samples had to be sent to the institute from all over the soviet union and now the institute has one of the largest phage collections in the world. It has continued giving phage therapies to patients for decades, up until this day. Definitely not mainstream but don't call it untested!

[1]: https://en.wikipedia.org/wiki/George_Eliava_Institute