In vitro antimicrobial susceptibility. (A) MIC distributions for 13 antimicrobial agents against 185 C. difficile. VAN, vancomycin; MTZ, metronidazole; FDX, fidaxomicin; RFX, rifaximin; AMC, amoxicillin-clavulanate; CLI, clindamycin; ERY, erythromycin; CRO, ceftriaxone; MEM, meropenem; MXF, moxifloxacin; TET, tetracycline; TZP, piperacillin-tazobactam; TMP, trimethoprim. Where available, established susceptible and resistant breakpoints are indicated by vertical green and red lines, respectively. (B) Plots showing overall percentage of nonsusceptibility and percentage of phenotypic-genotypic concordance for the TetR (tetracycline-resistant), FQR (fluoroquinolone-resistant), and MLSB (macrolide-lincosamide-streptogramin B-resistant) phenotypes.