Table 1.

Susceptibility profile relationship with type of β-lactamase

pI by IEF (no. of strains)No. (%) of strains resistant toa:
AMPAMP + CLAMEZMEZ + CLACARCEF
5.4 (10)10 (100)6 (60)9 (90)0 (0)10 (100)6 (60)
7.6 + 5.4 (20)20 (100)8 (40)11 (55)1 (5)20 (100)11 (55)
7.6 (34)34 (100)6 (18)17 (50)0 (0)34 (100)19 (56)
7.6 + 7.1 (20)20 (100)2 (10)9 (44)0 (0)20 (100)6 (30)
7.1 (13)13 (100)0 (0)2 (15)0 (0)12 (92)2 (15)
  • a AMP, ampicillin; CLA, clavulanic acid; MEZ, mezlocillin; CAR, carbenicillin; CEF, cephalothin. The following breakpoints were used: for ampicillin, ampicillin-clavulanic acid, and cephalothin, ≥16 μg/ml; for mezlocillin and mezlocillin-clavulanic acid, ≥64 μg/ml; for carbenicillin, ≥32 μg/ml.