Biology Reference
In-Depth Information
Table 2.
Minimum Bactericidal Concentrations.
Formulations
MBC (mg/L)
CAMH broth
Inhibitory factors
Free tobramycin
1
16
Lipo tobramycin
2
8
Free polymyxin B
0.5
32
Lipo polymyxin B
0.25
16
Bactericidal activity of free and liposomal formulations against susceptible
P. aeruginosa
ATCC 27853 strain was
carried out inbroth aloneor inpresence of DNNF-actin /LPS/L TA at a fi nal concentration of 1000 m /L.
Antibacterial Activity on CF Sputum
To test the efficacy of entrapped versus free antibiotics in the CF sputa, pooled sputum
was diluted and incubated with increasing concentrations of tobramycin and poly-
myxin B for 18 hr. As shown in Figure 4, bacterial counts were reduced, but neither
of the formulations eradicated endogenous bacteria present in the sputum. Liposomal
tobramycin (128 mg/l; 5.3 ± 0.1 logs) and polymyxin B (8 mg/l; 3.8 ± 0.1 logs) dis-
played higher bactericidal activity than free tobramycin (512 mg/l; 5.4 ± 0.2 logs) and
polymyxin B (32 mg/l; 3.9 ± 0.1 logs). The sputum itself did not seem to have any
antibacterial activity against endogenous strains as bacterial counts were increased
from 0 hr (5.2 ± 0.1 logs) to 18 hr (7.8 ± 0.1 logs).
Figure 4.
CF Sputum treatment with various antibiotic formulations. CFU counts were made after
incubation of diluted CF sputum (1:10 w/v) in PBS with two-fold dilutions of free tobramycin at 512
mg/l (F-TOB), liposomal tobramycin at 128 mg/l (L-TOB), free polymyxin B at 32 mg/l (F-PMB), and
liposomal polymyxin B at 8 mg/l (L-PMB). Growth controls are represented at 0 hr (empty bar), and
18 hr (dark bar).
