Quantitative Insights and Visualization of Antimicrobial Tolerance in Mixed-Species Biofilms

Biofilms are a major problem in hard-to-heal wounds. Moreover, they composed of different species and often tolerant to antimicrobial agents. At the same time, interspecific synergy and/or competition occurs when some bacterial clash. For this reason, tolerance two dual-species wound biofilm models Pseudomonas aeruginosa Staphylococcus aureus or Enterococcus faecium against antimicrobials dressings were analyzed quantitatively by confocal laser scanning microscopy (CLSM). The results compared findings with planktonic bacteria. Octenidine-dihydrochloride/phenoxyethanol polyhexamethylene biguanide (PHMB) irrigation solutions showed significant, albeit delayed reduction bacteria, while PHMB dressing was not able induce effect. However, cadexomer-iodine caused sustained killed almost all bacteria down 102 cfu/mL within 6 days control (1010 cfu/mL). By means CLSM untreated human models, it became evident that P. dominates over E. S. aureus. Additionally, appeared as vast layer at bottom samples, formed grape-like clusters. In second model, distribution even clearer. Only few visible, contrast aeruginosa. It seems avoid each other seek their respective niches. These mixed-species efficacy substances nearly species-independent. Their frequent application appears be important. remains challenge treatment requires new, combined therapy options.