Small hydrophilic antibiotics, such as β-lactams, tetracycline, P505-15 supplier fluoroquinolones

etc., use porin channels to cross the outer membrane and diffuse very well [39]. For this reason, they do not take advantage by the disruption of membranes; thus their association with polysorbate 80 is indifferent. Conclusions In conclusion, polysorbate 80 shows a bactericidal activity against H. pylori and exerts a synergistic Quisinostat mouse effect with some chemotherapics. We therefore propose such compound for the treatment of H. pylori infection in association with antibiotics. Methods Determination of MBC The 22 strains used are listed in Table 1. The whole study was conducted following the approval of the local University Hospital Ethics Committee. All patients gave a written informed consent prior to inclusion of strains isolated from them in the study. Bacterial suspensions were stored in glycerol broth at −80°C until the MBC determination was carried out. Suspensions were thawed and subcultured twice in selective Brucella agar plates (Pylori plates, BioMérieux, Italia S.p.A., Rome, Italy.) containing 10% foetal calf serum and 10 mg/L of each vancomycin, trimethoprim, GS-1101 in vivo and amphotericin B and 5 mg/L of cefsulodin. Plates

were incubated in jars with a microaerobic environment generated using Campy Pak sleeves (Oxoid Ltd., Basingstoke, England). Polysorbate 80 and antibiotics -amoxicillin, clarithromycin, metronidazole, tetracycline and levofloxacin- (Sigma Aldrich-Milan, Italy) were dissolved in sterile water containing (when necessary) 4% of DMSO, sterilized by filtration and double

diluted in Megestrol Acetate Brucella broth containing 10% foetal calf serum, 10 mg/L of each vancomycin, trimethoprim, and amphotericin B and 5 mg/L of cefsulodin (to avoid contaminations). One microwell contained plain broth and was the control. Tests were carried out in triplicate in a final volume of 0.1 mL, using Microtiter® plates. H. pylori suspensions were prepared starting from cultures on Brucella agar with 10% foetal calf serum incubated in a microaerobic environment for 48 h. The bacterial suspensions were then added to each microwell at a final concentration of approximately 106 colony-forming units per mL. After 24 h of incubation under microaerobic conditions at 37°C, 3 μL of broth from each dilution were deposited onto Brucella agar plates, which were incubated for 3–5 days in a microaerobic atmosphere at 37°C. The lowest concentration in broth, for which the subculture on agar showed complete absence of growth, was considered the MBC. Results are the average of three determinations. Determination of antimicrobial activity of polysorbate 80 associated with antibiotics Tests to evaluate the possible synergistic effect of polysorbate 80 associated with antibiotics were performed on all strains.