TABLE 2

MICs of 63 strains of commensal streptococci divided by species designation

Antibiotic and MIC (μg/ml)No. (%) of strainsNo. (%) of strains of species:
S. mitis (n = 46)S. oralis (n = 10)S. infantis (n = 6)S. pseudopneumoniae (n = 1)
Benzylpenicillin
    ≤0.2530 (48)21 (46)7 (70)1 (17)1
    >0.25–211 (17)9 (19)1 (10)1 (17)
    >222 (35)16 (35)2 (20)4 (66)
    Median1.01.00.18754.0
Piperacillina
    ≤0.2522 (35)15 (33)6 (60)1
    >0.25–215 (24)11 (24)1 (10)3 (50)
    >226 (41)20 (43)3 (30)3 (50)
    Mean1.01.00.1252.5
Oxacillina
    ≤0.2515 (24)12 (26)2 (20)1
    >0.25–215 (24)10 (22)4 (40)1 (16)
    >233 (52)24 (52)4 (40)5 (84)
    Median4.04.01.2512.0
Cephalothinb
    ≤0.516 (25)14 (30)1 (10)1
    >0.5–210 (16)5 (11)4 (40)1 (16)
    >237 (59)27 (59)5 (50)5 (84)
    Median8.04.03.08.0
Cefuroxime
    ≤0.524 (39)18 (40)5 (50)1
    >0.5–11 (2)1 (16)
    >137 (59)27 (60)5 (50)5 (84)
    Median4.04.01.254.0
Cefotaxime
    ≤0.527 (44)20 (44)6 (60)1
    >0.5–218 (29)11 (25)2 (20)5 (84)
    >217 (27)14 (31)2 (20)1 (16)
    Median2.02.00.2822.0
  • a No resistant breakpoints for the mitis group of streptococci are given by EUCAST. Breakpoints for benzylpenicillin are used for comparison.

  • b No resistant breakpoints for the mitis group of streptococci are given by EUCAST. Breakpoints for cefotaxime are used for comparison.