TABLE 3.

Antibiotic susceptibility of P. aeruginosa PAO1 and mutant strains grown with polyamines or their precursors

P. aeruginosa strain and growth conditionsMICs (μg/ml)a
Px-BCOLKANGENCIPNORTETEtBrACO
PAO1 grown with
    MMPb22640.50.060.25825664
    MMP (20 μM MgSO4)c8825620.060.25825664
    MMP + spermidine16162562128>512512
    MMP + spermine (1 mM)4412810.2518>512256
    MMP + putrescine2225620.518512256
    MMP + cadaverine2225620.120.58512256
    MMP + agmatine2225620.120.58512256
    MMP + ornithine22640.50.060.25825664
    MMP + arginine22640.50.060.25825664
    MMP + lysine22640.50.060.25825664
PAO1 (spuF::Tc) grown with MMP + spermidine1616640.50.060.25>100>512512
PAO1 (spuH::Tc) grown with MMP + spermidine1616640.50.060.25>100>512512
  • a MIC measurements were repeated three times with identical results by broth dilution methods as described in Materials and Methods. Values in boldface indicate increases in the MICs of the tested antibiotics. Px-B, polymyxin B; COL, colistin; KAN, kanamycin; GEN, gentamicin; CIP, ciprofloxacin; NOR, norfloxacin; TET, tetracycline; EtBr, ethidium bromide; ACO, acridine orange.

  • b MMP contains 1 mM MgSO4, and 20 mM concentrations of glutamate and other supplements unless otherwise indicated.

  • c MMP containing 20 μM MgSO4 with incubation of 20 h.