Cyanobacterium Chroococcus sp. Mediated Silver Nanoparticles to Fight Candida albicans and Staphylococcus aureus...

Biofilm structure enables microorganisms to survive in adverse environmental conditions, and biofilm-related infections are an increasing global public health concern. Information on the structure and interactions of polymicrobial biofilms, which generally contain more than one species in nature and in vivo, is also quite limited. Candida albicans and Staphylococcus aureus, important opportunistic pathogens, are frequently co-isolated together in infections and exhibit increased resistance to treatment. Silver nanoparticles (AgNPs) have been proposed as effective agents against antimicrobial-resistant strains, but synthesis by traditional methods has negative effects on the environment and health. In this study, the effects of cyanobacterium Chroococcus-mediated AgNPs on planktonic and biofilm-formed single and dual S. aureus ATCC 25923 and C. albicans ATCC 14053 strains were investigated for the first time to our knowledge. The MIC test results obtained showed that S. aureus ATCC 25923 was much more sensitive to AgNPs, whereas resistance to amphotericin B and ampicillin increased in dual culture. Scanning and transmission electron microscopic findings, biofilm reduction test, hydrophobicity determination, and confocal microscopic data revealed that AgNPs acted with multi-targets on cell wall and membrane structures, cytoplasm, and organelles in single and dual cultures and had antibiofilm effects. XTT test results demonstrated the biofilm-reducing effect of AgNPs, but this effect was diminished in dual species biofilms compared to single biofilms. In addition, application of AgNPs before biofilm formation is much more effective than application after biofilm formation. Interestingly, the effect of ampicillin on dual biofilm structure was greater than on single biofilm, suggesting that bacterial lysis induced by ampicillin may disrupt fungal biofilm structure or that environmental changes following lysis suppress biofilm development. Our data support that Chroococcus-mediated AgNPs have promising potential in biofilm management, although elucidating the mechanisms underlying the observed limited resistance in dual biofilms remains important.