Characterization of a novel antimicrobial surface and its effectiveness against important pathogens

  • Maria Teresa de Moura Pereira Bento de Carvalho (Student)

Student thesis: Master's Thesis


The survival and spread of resistant foodborne and nosocomial-associated bacteria through high-touch surfaces is not always prevented by the employment of cleaning protocols. Antimicrobial surface coatings surge from the need to eradicate pathogenic bacteria and prevent future infections and even outbreaks. This study aimed to characterize a novel QAC-based coating in terms of cytotoxicity, kinetics, and durability and to determine its ability to inhibit important health-associated pathogens on different surface materials (polyvinyl chloride, glass, and stainless steel). Preliminary efficacy of the novel antimicrobial coating was conducted against several Gram-positive and -negative bacteria. Their growth was inhibited after direct contact, and three relevant pathogens were selected to proceed with the study - Acinetobacter baumannii ESB260, Escherichia coli ATCC 25922, and Listeria monocytogenes Scott A. Both E. coli and L. monocytogenes were sensitive to all antibiotics tested, unlike A. baumannii that was resistant. In addition, all the pathogens presented similar temperature and pH susceptibility profiles. The antimicrobial activity of the coating and its durability on tested surfaces were assessed through an international standard developed by the International Organization for Standardization, (ISO). None of the pathogens were able to survive within 1-minute of contact time on each coated surface. However, despite its quick contact killing time, the durability of the antimicrobial coating on each surface, after 7 days, was not promising. No antimicrobial activity was observed against all the pathogens on the coated surfaces after cleaning with a wet cloth, bleach, and a commercial degreaser, except E. coli and L. monocytogenes which were both inhibited on glass surfaces treated with the commercial degreaser. Bactericidal activity and minimum inhibitory concentrations for the product were also assessed. Cytotoxicity of the compound was investigated through MTT assay; concentrations as low as 5% (v/v) were revealed to be cytotoxic towards both human keratinocyte cells and mouse fibroblast cells. However, no vestigial concentrations of antimicrobial coating (≤0.3125% v/v) were cytotoxic to human colorectal adenocarcinoma cells. Further tests are required, especially regarding the treatments to assure the coating's durability, but it is clear that this novel coating is promising to eliminate clinically relevant pathogens.
Date of Award27 Oct 2021
Original languageEnglish
Awarding Institution
  • Universidade Católica Portuguesa
SupervisorJoana Inês Bastos Barbosa (Supervisor) & Paula Teixeira (Co-Supervisor)


  • Antimicrobial activity
  • Quaternary ammonium compounds
  • Touch surfaces


  • Mestrado em Microbiologia Aplicada

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