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Table 2 Antibiotic susceptibilities of five biofilm-positive isolatesa grown in different modes.

From: Antibiotic susceptibility of coagulase-negative staphylococci isolated from very low birth weight babies: comprehensive comparisons of bacteria at different stages of biofilm formation

Isolate and mode of growth Initial bacterial density (CFU/ml) Penicillin (μg/ml) Gentamicin (μg/ml) Oxacillin (μg/ml) Vancomycin (μg/ml) Ciprofloxacin (μg/ml) Rifampicin (μg/ml)
   MIC MBC MIC MBC MIC MBC MIC MBC MIC MBC MIC MBC
RP62A              
Log Planktonic (2.6-7.3)× 105 8 8 16 32 64 64 2 2 0.06 0.12 0.008 0.03
Monolayer (6.0-15.6) × 105 32 128 c 64 64 16 64 2 8 0.12 0.12 0.002 0.008
Stat Planktonic (0.2-0.5) × 109 b > 1024   1024   > 1024   32   ≤1   32
Biofilm (0.9-1.9) × 109 >1024e >1024 64 >1024 64 >1024 16 >1024d 0.25 >1024 0.004 0.015
Isolate 3
Log Planktonic (2.9-8.3) × 105 8 16 0.25 0.25 0.25 0.25 2 4 0.12 0.25 0.008 0.015
Monolayer (5.0-11.0) × 105 32 64 0.25 0.5 0.12 0.5 2 8 0.25 0.5 0.002 0.004
Stat Planktonic (0.6-2.2) × 109   >1024   32   >1024   > 1024   1024   256
Biofilm (0.3-1.3) × 109 >1024 >1024 16 16 0.25 2 16 16 0.25 2 0.5 4
Isolate 8a
Log Planktonic (2.6-5.5) × 105 128 128 32 32 8 8 1 2 0.25 0.25 0.008 0.03
Monolayer (6.4-11.1) × 105 >128 >128 32 64 64 64 1 8 0.12 0.5 0.004 0.015
Stat Planktonic (4.4-4.9) × 108   >1024   >1024   >1024   >1024   1024   2
Biofilm (0.6-1.8) × 108 1024 >1024 256 >1024 256 >1024 8 >1024 0.12 >1024 0.004 4
Isolate 9
Log Planktonic (3.1-5.2) × 105 32 64 32 32 8 16 1 2 0.25 0.25 0.015 0.03
Monolayer (4.6-10.8) × 105 >128 >128 32 >128 16 32 2 8 0.25 0.5 0.004 0.015
Stat Planktonic (0.7-0.8) × 109   >1024   >1024   >1024   >1024   >1024   256
Biofilm (1.1-1.7) × 109 >1024 >1024 64 >1024 >128 >1024 8 >1024 0.25 >1024 0.008 4
Isolate 11
Log Planktonic (2.7-8.5) × 105 8 8 64 >128 32 64 1 1 0.06 0.12 >128 >128
Monolayer (3.2-17.8) × 105 32 64 >128 >128 32 64 1 2 0.06 0.12 >128 >128
Stat Planktonic (0.8-1.6) × 109   >1024   >1024   >1024   >1024   512   1024
Biofilm (0.2-0.6) × 109 >1024 >1024 256 >1024 256 >1024 8 >1024 0.25 16 64 >1024
  1. α Biofilm-positive isolates (OD600 >0.24).
  2. b MICs for CoNS at stationary phase are not provided as the values could not be determined by standard methods.
  3. c Values underlined indicate a significant increase in the MICs or MBCs between log-planktonic and adherent monolayer modes of growth.
  4. d Values in italic indicate a significant change in the MBCs between stationary-planktonic and biofilm modes of growth.
  5. e Values in bold indicate a significant increase in MICs or MBCs between log-planktonic/adherent monolayer and biofilm modes of growth