despite these favourable pharmacokinetic properties and notable effects against bacterial biofilms, the emergence of CP-690550 nmr resistance can preclude its use as a single agent. The use of combination antimicrobial regimens with FOS could help to reduce the risk of antimicrobial resistance as well as provide a synergistic effect with other antimicrobials including beta-lactams, aminoglycosides, and fluoroquinolones [22, 25, 26]. Interestingly, synergistic studies have demonstrated that FOS may even decrease the level of penicillin-resistance in pneumococci by AZD0156 chemical structure altering the degree of expression of penicillin-binding proteins . When used in combination, FOS appears to exert substantial antimicrobial activity and may be clinically effective against infections caused specifically by “problem” Gram-positive cocci pathogens both in vitro and in vivo [28, 29]. In support to this, we found that FOS in combination with CLA is highly effective in reducing biofilm biomass in vitro, more so than either therapy alone. We suggest that this may be an effective therapy to reduce biofilm-related wound infections. Further study is warranted to test its impact in vivo; this study lays the foundation for that work. Results and discussion Structurally unrelated to other antimicrobials, FOS uniquely inhibits the first
step of peptidoglycan biosynthesis in bacterial cell wall by binding to UDP-N-acetyl-glucosamine LY2835219 supplier enolpyruvate transferase . Its low molecular weight (194.1 Da) and non-reactivity with the negatively charged bacterial glycocalyx allows for
efficient diffusion into tissues and the biofilm matrix . This may explain its enhanced antimicrobial activity against biofilm embedded bacteria, as it has been shown to destabilize biofilms and thereby enhance the permeability of other antimicrobials [20, 22, 31]. Fosfomycin and clarithromycin synergistic activity Microtitre plate assay (MPA) results identified synergism between CLA and FOS in reducing biofilm production. Fractional inhibitory concentration index (FICI) values (Table 1) revealed fractional about synergy (FICI ≤ 0.5) of 0.31 to 0.56 in the FOS and CLA resistant strains. As a set 1:1 combination of FOS and CLA (Breakpoint dose for CLA resistance is ≥ 8 μg/ml) was chosen, the FIC may be lower based on specific MIC against biofilm for each strain. In comparison with the control samples, low doses of FOS at 8 μg/ml (P > 0.05) and CLA at 8 μg/ml (P > 0.05) independently produced no significant reduction in biofilm production, whereas treatment with FOS and CLA in combination resulted in a significant (P < 0.05) reduction in the bacterial biomass (Figure 1) in one-way ANOVA models. To ensure that this impact was directed against biofilm formation and was not simply inhibiting bacterial growth both FOS resistant (≥64 μg/ml) and CLA resistant (≥256 μg/ml) strains were chosen.