Comparative <em>In Vitro Staphylococcus aureus</em> Biofilm Evaluation on 3D-Printed Polylactic Acid and Polyethylene Terephthalate Glycol-modified Surfaces

Three-dimensional (3D) printing has accelerated the development of customized medical devices, but biofilm formation on printed materials remains a major threat to implant safety and performance. Because material chemistry and print-dependent surface features can influence bacterial attachment and antibiotic tolerance, standardized in vitro approaches that enable meaningful comparisons across commonly used 3D-printing polymers are needed. Here, we compare biofilm development on polylactic acid (PLA) and polyethylene terephthalate glycol (PETG) using a multi-model in vitro evaluation framework that captures complementary aspects of biofilm biology, including early adhesion, maturation, and antimicrobial tolerance, under both static and flow conditions. S. aureus biofilms were established and assessed using quantitative (viable bacterial load and minimal biofilm eradication concentration [MBEC]) and qualitative (scanning electron microscopy) endpoints. Both PLA and PETG supported biofilm formation across models; however, PLA tended to show higher early adhesion and greater biofilm density. In static assays, PLA demonstrated higher CFU values than PETG, whereas vancomycin MBEC values were similar between materials. Assay-dependent differences in MBEC were observed across platforms, underscoring how model structure can influence apparent antimicrobial susceptibility. Under dynamic flow, biofilm burden increased relative to static conditions, with minimal material-dependent differences. Collectively, these results highlight the susceptibility of both polymers to biofilm formation and demonstrate the value of a multi-model framework for evaluating material-associated biofilm behavior and benchmarking antimicrobial performance on 3D-printed device-relevant substrates.