Complex sentence: An entirely different approach is phage therapy (e.g., at the Eliava Institute in Georgia), which in mice had a reported efficacy against up to 95% of tested "Staphylococcus" isolates.
Split into simpler sentences: An entirely different approach is phage therapy (e.g., at the Eliava Institute in Georgia). Experimental phage therapy tested in mice had a reported efficacy against up to 95% of tested "Staphylococcus" isolates.