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Chisari G., Drago L., De Vecchi E., Reibaldi M.
Aim. The authors evaluated the in vitro effects of a sub-inhibitory concentration of fusidic acid and gentamicin on adherence of coagulase-negative staphylococci to polymethyl methacrylate (PMMA), heparin-surface-modified (HSM) and hydrophobic acrylic (HA) intraocular lenses (IOLs).
Methods. Five clinical isolates of Staphylococcus epidermidis (strains CMO-1, CMO-3, CMO-4, CMO-5 and CMO-7) were chosen for their ability to produce slime. Minimum inhibitory concentrations (MIC) were determined by a broth microdilution method. For adhesion experiments, each strain (about 10 CFU/ml) was inoculated into Tryptic Soy broth containing fusidic acid or gentamicin at a concentration of 1/6 X MIC or no antibiotics (control), and incubated for 4 hours at 37°C. Then, IOLs were immersed into these bacterial cultures and removed after 30, 60 and 180 minutes. Bacterial adhesion to IOLs was evaluated by bacterial counts and confirmed by scanning electron microscopy.
Results. Minimum inhibitory concentrations of fusidic acid and gentamicin ranged from 0.19 to 0.78 mg/L and from 0.78 to 3.12 mg/L, respectively. Control samples evidenced a more marked adhesive activity to HA and PMMA IOLs than to surface of HSM PMMA IOLs. Both fusidic acid and gentamicin were able to significantly reduce the adhesion of S. epidermidis to all the IOLs surfaces at subinhibitory concentrations when compared with untreated IOLs.
Conclusion. Our data confirmed the excellent activity of fusidic acid and gentamicin against bacterial adhesion to IOLs and the role of heparin in reducing adhesion to PMMA IOLs.