Date of Award

8-2025

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Microbiology

Committee Chair/Advisor

Xuiping Jiang

Committee Member

Harry Kurtz Jr.

Committee Member

Kristi Whitehead

Committee Member

David Buckley

Abstract

Biofilms are resistant to many stressors including disinfectant treatments. Disinfection may be further complicated by biofilms formed on damaged surfaces, as the damaged parts provide bacteria a better place to attach and grow. To better understand the risks, a new method to standardize surface scratching, to emulate worn surfaces via surface roughness changes was developed. These surfaces were used to grow biofilms with an adapted standardized EPA method to determine disinfection efficacy differences on scratched and non-scratched high-density polyethylene (HDPE) and stainless steel (SS) coupons treated with commercial disinfectants [hypochlorite (CL)-based, hydrogen peroxide (HP)-based, and quaternary ammonium (QA)-based]. Post-80 grit sandpaper scratching, average surface roughness of SS and HDPE increased by 0.82 µm and 12.69 µm, respectively. Early-phase biofilms were more pronounced on 80 grit-scratched surfaces versus smooth surfaces; no significant difference for mature biofilms was detected. Disinfection treatments achieved biofilm log reductions/coupon ranging from 3.23 to 6.22 (Pseudomonas aeruginosa) and 2.92 to 5.62 (Staphylococcus aureus). Biocide comparisons revealed HP and CL disinfectants performed significantly better than QA on HDPE. CL and QA performed significantly better than HP on SS against P. aeruginosa. The desired 6 log/coupon reduction was only achieved against P. aeruginosa grown on a non-scratched HDPE coupon treated with CL. Overall, bacteria, surface material, roughness, and disinfectants affected the biofilm disinfection.

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