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Table 3 Antibiotic susceptibility of four biofilm-negative 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
SP2
Log Planktonic (1.2-4.1) × 105 0. 5 0. 5 8 8 0.06 0.06 1 2 0.12 0.12 0.008 0.03
Monolayer (2.6-4.7) × 105 2 8 c 16 16 0.12 0.12 0.5 1 0.12 0.12 0.004 0.008
Stat Planktonic (3.5-9.5) × 107 b >1024   1024 d   2   4   2   0.008
Biofilm (1.0-3.2) × 107 128 >1024e 8 32 0.12 2 2 4 0.12 2 0.002 0.008
Isolate 15
Log Planktonic (2.2-5.5) × 105 128 128 32 64 16 32 4 4 0.25 0.25 0.015 0.03
Monolayer (5.2-16.4) × 105 >128 >128 32 64 16 64 4 8 0.12 0.25 0.004 0.008
Stat Planktonic (3.7-7.9) × 108   >1024   >1024   >1024   >1024   >1024   64
Biofilm (0.7-0.9) × 108 >1024 >1024 256 >1024 256 >1024 16 >1024 0.25 512 0.004 0.008
Isolate 19
Log Planktonic (2.9-7.4) × 105 >128 >128 64 64 2 8 2 2 0.25 0.25 0.008 0.015
Monolayer (3.2-14.6) × 105 >128 >128 64 >128 2 8 2 8 0.12 0.25 0.002 0.008
Stat Planktonic (0.7-1.5) × 109   >1024   >1024   >1024   >1024   1024   2
Biofilm (0.1-0.2) × 109 1024 >1024 64 >1024 64 >1024 4 >1024 0.25 4 0.008 0.06
Isolate 22
Log Planktonic (2.8-5.6) × 105 >128 >128 64 64 8 16 4 4 0.12 0.25 0.015 0.03
Monolayer (4.8-16.3) × 105 >128 >128 32 >128 32 32 2 8 0.12 0.25 0.004 0.008
Stat Planktonic (0.5-0.7) × 109   >1024   >1024   >1024   >1024   >1024   256
Biofilm 0.2 × 109 1024 >1024 >128 >1024 >128 >1024 16 >1024 0.25 1 0.008 0.03
  1. a Biofilm-negative isolates included biofilm-weak producer (0.24 >OD600≥ 0.12) and biofilm-negative producer (OD600 <0.12).
  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 italics 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.