Supplementary Material for: Anti-Infective Properties of <i>Lactobacillus fermentum</i> against <i>Staphylococcus aureus</i> and <i>Pseudomonas aeruginosa</i>

Surgical wounds and implant-associated <i>Staphylococcus aureus</i> and <i>Pseudomonas aeruginosa </i>infections are often difficult to treat because of limited susceptibility of several of these strains to conventional antibiotics. As a result, there is a constant need for new alternative drugs. The aim of this study was to investigate the antimicrobial properties of <i>Lactobacillus fermentum, </i>a probiotic bacterium, which we have isolated from colonic biopsies. The inhibition of <i>S. aureus</i> and <i>P. aeruginosa</i> growth was evaluated by coincubating with <i>L. fermentum</i> strains. Growth inhibition was tested for several of their clinical isolates using agar well diffusion assays. For biofilm assay <i>S. aureus</i> and <i>P. aeruginosa</i> were grown on the glass slides and in 96-well plates in presence of 2.5 µg/ml culture filtrate of <i>L. fermentum</i>. Biofilms were photographed using confocal microscope or stained with 0.1% crystal violet. Reduction in the cytotoxicity of <i>S. aureus</i> and <i>P. aeruginosa </i>was observed in presence of 2.5 µg/ml <i>L. fermentum</i>-spent media. Using in vitroexperiments, we showed that <i>L. fermentum</i>-secreted compound(s) inhibits the growth, cytotoxicity and biofilm formation of several <i>S. aureus</i> and <i>P. aeruginosa</i> strains. Compound(s) present in the culture supernatant of <i>L. fermentum</i> may have promising applications in treating hospital-acquired infections.