TABLE 2.

Susceptibilities of mature (48-h-old) colony biofilms to antibiotics

AntibioticLRa (mean ± SEM)% Protection explained byb:
Lack of oxygenLack of oxygen for 24 h
None0.14 ± 0.07
Ciprofloxacin1.13 ± 0.146284
Tobramycin0.52 ± 0.126970
Ceftazidime0.82 ± 0.02>110>110
Chloramphenicol0.05 ± 0.0395109
Carbenicillin0.53 ± 0.12NCNC
Tetracycline0.21 ± 0.0580105
  • a LR, log reduction.

  • b The maximum percentage of biofilm protection that can potentially be explained by oxygen deprivation was calculated as [(log reduction for aerobic 4-h-old biofilm − log reduction for anaerobic 4-h-old biofilm)/(log reduction for aerobic 4-h-old biofilm − log reduction for 48-h-old biofilm)] × 100. NC, not calculated because killing in 48-h-old biofilms was greater than that in 4-h-old biofilms.