TABLE 6.

ED50s of combinations of piperacillin and penem molecules for murine acute lethal infections with various pathogens

CompoundbED50 (mg/kg) (95% confidence limits)a for infection with:
TEM-1-producing E. coliTEM-29- and OXA-1-producing E. coliCMY-2-producing E. coliAmpC-producing Enterobacter aerogenes
PIP alone165.8 (120-231)127.3 (60.7-227)101.8 (38-430)421 (191-1,648)
PIP-A30.4 (22.5-41.4)44.1 (31.1-66.9)NTNT
PIP-B21.8 (15.9-29.7)53.1 (33.5-108.4)14.4 (10.8-19.3)100.8 (49-463)
PIP-C19.5 (13.9-26.9)78.7 (64.3-96.7)22.4 (15.9-34.2)102 (50-243)
PIP-D22.8 (16.3-31.7)67.6 (39.2-129)14.2 (8.9-19.4)96.4 (46.2-185)
PIP-E24.5 (16.5-38.2)44.4 (31.2-67.5)NT98.1 (68.4-154)
PIP-F20.0 (15.1-26.5)37.4 (21.8-65.9)15.1 (10.3-20.3)125.3 (71.6-214)
PIP-G31.8 (23.9-43.1)37.6 (21.9-66.2)14.9 (9.6-20.5)123.2 (62.1-241)
PIP-TZB46.4 (33.9-67.5)NT35.4 (24.1-54.5)NT
LD50c (CFU)5 × 1024.7 × 1025.1 × 1031.8 × 106
  • a The ED50s listed correspond to the efficacy of piperacillin. NT, not tested.

  • b Piperacillin (PIP)-inhibitor at a 4:1 ratio. TZB, tazobactam.

  • c LD50, 50% lethal dose of organism in each infection.