An Investigation of Cellulase and Epigallocatechin-3-gallate as Enhancers of Antibiotic Efficacy in Polymicrobial Biofilm Treatments

I. Abstract The treatment of bacterial infections is becoming increasingly difficult with the alarming rise of antibiotic resistance. Research has illustrated that the majority of these infections are composed of polymicrobial biofilms that can withstand antibiotic treatment to a higher degree than single-species microbial communities. Nonetheless, monospecies biofilms are still utilised for the investigation of novel combinatorial treatments, risking failure to transfer results to in vivo infections. This study aims to provide evidence that novel combinatorial therapies can enhance the efficacy of antibiotics in treating multispecies biofilm infections. Expanding on work within the field concerning the antibiofilm compounds epigallocatechin-3-gallate and cellulase, we sought to analyse the effects of cellulase and epigallocatechin-3-gallate, in combination with ampicillin, on polymicrobial biofilms. We pursued this by performing crystal violet assays and measuring colony-forming unit counts on environmental samples following combinatorial treatments. Statistical analysis demonstrated that cellulase significantly reduced both biofilm biomass and viable bacteria while epigallocatechin-3-gallate did not affect either quantifier. Whilst these results were not completely in line with expectations, the pronounced effect of cellulase and the epigallocatechin-3-gallate ethanol solvent were considered significant contributions to polymicrobial combinatorial treatment research. With further work in this space identifying additional therapies and examining compounds in vivo, there is the potential for millions of lives to be saved and the threat of a pandemic of antimicrobial resistance to be countered. Competing Interest Statement The authors have declared no competing interest.