Table 3.
Antibiotic susceptibility of four biofilm-negative isolatesa grown in different modes.
| 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 | 8c | 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 | 1024d | 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 |
a Biofilm-negative isolates included biofilm-weak producer (0.24 >OD600≥ 0.12) and biofilm-negative producer (OD600 <0.12).
b MICs for CoNS at stationary phase are not provided as the values could not be determined by standard methods.
c Values underlined indicate a significant increase in the MICs or MBCs between log-planktonic and adherent monolayer modes of growth.
d Values in italics indicate a significant change in the MBCs between stationary planktonic and biofilm modes of growth.
e Values in bold indicate a significant increase in MICs or MBCs between log-planktonic/adherent monolayer and biofilm modes of growth.