Strain-Dependent Effects of Glycosidases and Papain on Preformed Biofilm Biomass and Biofilm Formation in Escherichia coli

Biofilm formation by Escherichia coli can contribute to persistence and reduced susceptibility to antimicrobial treatment. Here, we evaluated treatment-associated changes following individual exposure to preparations of the glycosidases SdBgl1B and dispersin B (DspB) and the cysteine protease papain in assays assessing changes in preformed biofilm biomass and in biomass formed during 24 h of enzyme exposure across four E. coli strains (042, 1007, P180, and 23699) using static crystal violet microtiter-plate assays. The assays comprised three independent biological replicates with three technical wells per replicate for each condition. Papain-treated wells showed reductions in preformed crystal-violet-stained biomass of up to 92.4% for strain 042 at 1.00 mg/mL and 81.4–90.8% for strain 23699 across the tested concentration range. DspB-treated wells showed 67–72% less preformed biomass for strain 23699 and approximately 89% less biomass formed over 24 h by strain 042 at 0.03–0.06 mg/mL. Exposure to SdBgl1B was associated with variable responses, including approximately 62% less biomass formed by strain 042 at the enzyme concentration of 0.50 mg/mL. These percentages describe changes relative to the corresponding controls, not statistically established rankings among strains or enzymes. Several enzyme–strain combinations displayed non-monotonic responses, and some treatments produced crystal violet signals above the control. The control scheme does not resolve vehicle- or preparation-dependent staining contributions, precluding enzyme-specific causal attribution. Because crystal violet staining quantifies total attached stained material rather than specific matrix cleavage or bacterial viability, these findings document changes in the attached biomass endpoint but do not establish biofilm eradication, a molecular degradation mechanism, or bactericidal activity. Further matrix characterization, viability, dispersal, and confocal microscopy assays are required to determine mechanism and assess translational potential.