ABSTRACT MICs of 25 Abiotrophia defectiva and 109 Granulicatella adiacens isolates were determined by broth microdilution. Using CLSI breakpoints, the susceptibilities of A. defectiva and G. adiacens isolates were, respectively, 24% and 34% to penicillin, 92% and 22% to ceftriaxone, 48% and 3% to cefepime, 72% and 87% to meropenem, 92% and 10% to cefotaxime, 100% and 97% to levofloxacin, 92% and 80% to clindamycin, and 24% and 50% to erythromycin. All isolates were susceptible to vancomycin. In the penicillin-susceptible subgroup, all A. defectiva isolates were susceptible to ceftriaxone; however, 62% of G. adiacens isolates were ceftriaxone nonsusceptible.