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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.