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Updated: Mar 16, 2026
Antimicrobial Characterization of Advanced Materials for Bioengineering Applications
Published on: August 4, 2018
The Activity of Antimicrobial Surfaces Varies by Testing Protocol Utilized
Matias D Campos1, Paola C Zucchi1, Ann Phung1
1Department of Pharmacy and Health Systems Sciences, Northeastern University, Boston, Massachusetts, United States of America.
Background:
Contaminated hospital surfaces are an important source of nosocomial infections. A major obstacle in marketing antimicrobial surfaces is a lack of efficacy data based on standardized testing protocols.
Aim:
We compared the efficacy of multiple testing protocols against several "antimicrobial" film surfaces.
Methods:
Four clinical isolates were used: one Escherichia coli, one Klebsiella pneumoniae, and two Staphylococcus aureus strains. Two industry methods (modified ISO 22196 and ASTM E2149), a "dried droplet", and a "transfer" method were tested against two commercially available antimicrobial films, one film in development, an untreated control, and a positive (silver) control film. At 2 (only ISO) and 24 hours following inoculation, bacteria were collected from film surfaces and enumerated.
Results:
Compared to untreated films in all protocols, there were no significant differences in recovery on either commercial brand at 2 or 24 hours after inoculation. The silver surface demonstrated significant microbicidal activity (mean loss 4.9 Log10 CFU/ml) in all methods and time points with the exception of 2 hours in the ISO protocol and the transfer method. Using our novel droplet method, no differences between placebo and active surfaces were detected. The surface in development demonstrated variable activity depending on method, organism, and time point. The ISO demonstrated minimal activity at 2 hours but significant activity at 24 hours (mean 4.5 Log10 CFU/ml difference versus placebo). The ASTEM protocol exhibited significant differences in recovery of staphylococci (mean 5 Log10 CFU/ml) but not Gram-negative isolates (10 fold decrease). Minimal activity was observed with this film in the transfer method.
Conclusions:
Varying results between protocols suggested that efficacy of antimicrobial surfaces cannot be easily and reproducibly compared. Clinical use should be considered and further development of representative methods is needed.
Insights
Standardized testing protocols for antimicrobial surfaces yield inconsistent results, hindering clinical adoption. Further development of representative methods is crucial for reliable efficacy assessment.
Area of Science:
- Microbiology
- Materials Science
- Infection Control
Background:
- Contaminated hospital surfaces contribute to nosocomial infections.
- Lack of standardized efficacy data impedes antimicrobial surface market entry.
Purpose of the Study:
- Compare efficacy of multiple testing protocols for antimicrobial film surfaces.
- Evaluate standardized vs. novel methods for antimicrobial surface assessment.
Main Methods:
- Tested four clinical isolates (E. coli, K. pneumoniae, S. aureus) against commercial and developmental antimicrobial films.
- Utilized modified ISO 22196, ASTM E2149, dried droplet, and transfer methods.
- Enumerated bacterial recovery at 2 and 24 hours post-inoculation.
Main Results:
- Silver control showed significant microbicidal activity across most methods.
- Commercial antimicrobial films showed no significant difference from untreated controls in most tests.
- Developmental film exhibited variable efficacy depending on method, organism, and time.
- ISO and ASTM methods showed some efficacy, but results varied by organism and time.
Conclusions:
- Inconsistent results highlight challenges in reproducible antimicrobial surface efficacy comparison.
- Current standardized protocols may not accurately reflect real-world performance.
- Development of clinically relevant testing methods is essential.
