Effect of <i>Staphylococcus aureus</i> Cell-Free Culture Liquid on the Structure and Biochemical Composition of <i>Klebsiella pneumoniae</i> and <i>Pseudomonas aeruginosa</i> Biofilms

Recently acquired data suggest that many infections are associated with formation of multispecies biofilms, in which both antibiotic sensitivity and the permeability of the extracellular matrix differ from those of monocultures. In this work, we show that addition of cell-free culture liquid of Staphylococcus aureus to the biofilms of Klebsiella pneumoniae and Pseudomonas aeruginosa increased the content of α- and β-polysaccharides in the matrix up to twofold, which in turn probably affected the biofilm structure. Increased content of the polysaccharide component was also confirmed by a significantly increased expression of the K. pneumoniae pgaA gene and of the P. aeruginosa pelA and pslA genes in the presence of S. aureus culture liquid.