[Activation of formation of bacterial biofilms by azithromycin and prevention of this effect]

Growth of members of most of the studied genera of gram-positive (Dietzia, Kocuria, and Rhodo- coccus) and gram-negative bacteria (Pseudomonas and Chromobacterium) in biofilms exhibited higher resistance to an translation inhibitor, azithromycin compared to the growth of planktonic cultures of the same strains. Low concentrations of azithromycin were found to stimulate biofilm formation by the studied saprotrophic strains. The rate of synthesis of the polysaccharide matrix component exceeded the rate of cell growth, indicating implementation of the biofilm phenotype under these conditions. It was found that an alkylhydroxybenzene (AHB) compound 4-hexylresorcinol was capable of almost uniform suppression of growth of both planktonic cultures and biofilms of the saprotrophic strains under study. In some cases, combined action ofazithromycin and AHB resulted in an additive inhibitory effect and prevented the stimulation of biofilm growth by subinhibitory azithromycin concentrations. Thus, AHB may be considered a promising antibiofilm agent.