LAUSR

OBJECTIVES Biofilms associated with implantable medical devices and wounds are of clinical relevance, often requiring the repeated use of antibiotics without success. A search for non-antibiotic antimicrobial and anti-biofilm solutions is warranted, in line with Antimicrobial Stewardship. Our study aims to evaluate the broad-spectrum antimicrobial efficacy of tetrasodium-EDTA, ethanol and chlorhexidine hydrochloride alone and in combination against clinically relevant planktonic and biofilm cells of both bacterial and fungal pathogens. METHODS MICs and MBCs were determined for tetrasodium-EDTA, ethanol and chlorhexidine hydrochloride against planktonic cells of test pathogens. The MBEC Assay® biofilm inoculator device was used to evaluate the biofilm eradication ability of test antimicrobials alone and in combination against clinically relevant pathogens. Checkerboard micro-broth dilution assay was performed to analyze the synergism between the test antimicrobials. RESULTS Against planktonic cells, the combination of tetrasodium-EDTA with ethanol or chlorhexidine resulted in synergistic to indifferent activity with no antagonism observed. Against mature biofilms, all combinations were synergistic. The MBEC of each test antimicrobial was decreased from 4-to-64-fold when used in combination as compared to when agents were used alone. We optimized the concentration of antimicrobials to achieve rapid eradication of preformed biofilms. A triple-combination of 3% tetrasodium-EDTA, 20% ethanol and 2.5 µg/mL chlorhexidine-HCL completely eradicated 48-h-old-biofilms of all test strains within 2 h. CONCLUSION All three antimicrobial agents can be used together for prevention and treatment of biofilms and biofilm-related infections. The observedin vitro efficacy should be tested further through in vivo and clinical studies.