TABLE 2.
Bactericidal activity of gentamicin associated with a glycopeptide and selection of mutants resistant to the combinationsa
| Strain | Phenotypeb | Regulationc | Vancomycin plus gentamicin
|
Teicoplanin plus gentamicin
|
||
|---|---|---|---|---|---|---|
| Variation of log10 CFU in 24 h (mean ± SD) | Resistant mutantsd | Variation of log10 CFU in 24 h (mean ± SD) | Resistant mutantsd | |||
| JH2-2 | Vms Tes | NA | −(1.7 ± 1.4) | − | −(2.6 ± 1.0) | − |
| BM4281 | Vmr Tes | Vmi | +(0.3 ± 0.9) | + | −(4.6 ± 0.5) | − |
| BM4275 | Vmr Tes | Vmi | +(0.7 ± 0.8) | + | −(2.2 ± 1.6) | − |
| BM4309 | Vmr Ter | Vmi Tei | −(0.6 ± 1.3) | + | −(3.4 ± 1.3) | + |
| BM4310 | VmHet TeHet | Vmi Tei | +(0.8 ± 0.2) | + | −(4.0 ± 1.9) | + |
| BM4360 | Vmr Ter | Constitutive | +(0.3 ± 0.1) | + | +(0.6 ± 0.6) | + |
a
Bacteria (5 × 107 CFU/ml) were inoculated in broth containing gentamicin (4 μg/ml) and vancomycin (10 μg/ml) or teicoplanin (10 μg/ml) and incubated at 37°C for 24 h. Surviving bacteria and mutants were enumerated on agar or on agar containing the same antibiotics at the same concentrations.
b
Vm, vancomycin; Te, teicoplanin; s, susceptible; r, resistant; Het, heterogeneous.
c
NA, not applicable; Vmi, inducible by Vm; Tei, inducible by Te.
d
+, presence of mutants; −, absence of mutants.