Activity and Interactions of Liposomal Antibiotics in Presence of Polyanions and Sputum of Patients with Cystic Fibrosis - Recent Advances in Microbiology - page 87

Figure 3. Bactericidal activity and inhibition of antibiotics by LPS and LTA. A) Bactericidal
concentrations of free tobramycin (F-TOB) and liposomal tobramycin (L-TOB) were incubated in
presence of LPS/LTA (1 to 1,000 mg/l). B) Bactericidal concentrations of free polymyxin B (F-PMB)
and liposomal polymyxin B (L-PMB) were incubated in presence of LPS/LTA (1 to 1,000 mg/l).
Growth controls are represented at 0 hr (empty bar), and 3 hr (dark bar). Comparisons between
free and liposomal formulations were made by ANOVA one-way post t-test, and P-values were
considered significant when (***) p<0.001.
Since negatively charged polyanions hindered bactericidal activity in a short pe-
riod of time (3 hr exposure), their effect on the MBCs in an 18 hr period were also
investigated (Table 2). MBC levels increased 16-fold for free tobramycin (16 mg/l)
compared to 4-fold for its liposomal form (8 mg/l). Free (32 mg/l) and liposomal
polymyxin B (16 mg/) were inhibited equally by the polyanions (64-fold increase in
MBC).