In vitro FMEs of amoxicillin, gentamicin, ceftriaxone, and vancomycin against a reference strain of E. faecalis and two penicillin-resistant pneumococcal strains (strains PRP-1 and PRP-2). (A) FME of the combination (open circle), amoxicillin (increasing concentrations from the left; ▪), or gentamicin (increasing concentration from the right; ▴) against E. faecalis. (B) FME of the combination (open circle), amoxicillin (increasing concentrations from the left; ▪), or ceftriaxone (increasing concentration from the right; ▴) against strain PRP-1. (C) FME of the combination (open circle), vancomycin (increasing concentrations from the left; ▪), or ceftriaxone (increasing concentration from the right; ▴) against strain PRP-1. (D) FME of the combination (open circle), amoxicillin (increasing concentrations from the left; ▪), or ceftriaxone (increasing concentration from the right; ▴) against strain PRP-2. (E) FME of the combination (open circle), vancomycin (increasing concentrations from the left; ▪), or ceftriaxone (increasing concentration from the right; ▴) against strain PRP-2.