How Do We Determine the Efficacy of an Antibacterial Surface? A Review of Standardised Antibacterial Material Testing Methods

Abstract

Materials that confer antimicrobial activity, be that by innate property, leaching of biocides or design features (e.g., non-adhesive materials) continue to gain popularity to combat the increasing and varied threats from microorganisms, e.g., replacing inert surfaces in hospitals with copper. To understand how efficacious these materials are at controlling microorganisms, data is usually collected via a standardised test method. However, standardised test methods vary, and often the characteristics and methodological choices can make it difficult to infer that any perceived antimicrobial activity demonstrated in the laboratory can be confidently assumed to an end-use setting. This review provides a critical analysis of standardised methodology used in academia and industry, and demonstrates how many key methodological choices (e.g., temperature, humidity/moisture, airflow, surface topography) may impact efficacy assessment, highlighting the need to carefully consider intended antimicrobial end-use of any product.

A novel long-acting antimicrobial nanomicelle spray

“…The coat was always allowed to dry under aseptic conditions. The number of bacteria added was 50 µL of log 5.7 bacteria/slide which is the maximum reported bacterial density on surfaces used by the public [40]. Finally, to enumerate the amount bacteria that survived, normal saline was used, as the transfer media, and a negative control (uncoated glass slide) was used to enumerate the number of colonies survived on sterile slide without NM-3 [40].…”

Microbial resistance to nanotechnologies: An important but understudied consideration using antimicrobial nanotechnologies in orthopaedic implants

“…With these highly localized, precise, and controlled nano delivery modalities, bacterial resistance progression can be largely impeded; yet the uncertainty of their long-term stability in the physiological environment and ADME (absorption, distribution, metabolism and excretion) profile in vivo requires future investigation in order to fully verify their practicality for hospital use [ 154 ]. Importantly, majority of these drug delivery systems only kill 80–90% of bacteria, which is far below the clinically relevant antibacterial efficacy (2–3 log reduction) [ 155 ]. Additionally, whether there is sufficient penetration to access deep tissue via this delivery method remains to be observed.…”

“…One major problem is believed to be the sub-par reduction in bacteria for all these lab-based antibacterial nanotechnologies. A log-fold change of 2–3 is usually the threshold of efficacy of antimicrobial materials, pathogenic inhibition in vivo remains a cumbersome issue yet to be resolved for most of the past research [ 155 ]. The incomplete clearance of implant-residing bacteria is likely to generate persister cells and predispose the patients to antimicrobial resistance associated dire consequences.…”

Self-Healing and Antibacterial Essential Oil-Loaded Mesoporous Silica/Polyacrylate Hybrid Hydrogel for High-Performance Wearable Body-Strain Sensing

“…Besides, the sample size was 20 mm × 5 mm × 1.5 mm, and the stretching rate was obtained at 60 mm/min. The antibacterial activity of the hybrid hydrogel against Staphylococcus aureus and Escherichia coli was assessed using the shaking method. , Three parallel control samples were examined for all the samples (e.g., pure cotton fabrics, EO, control hydrogels, and hybrid hydrogels). The antibacterial properties exhibited by all the samples were determined based on GB/T 20944.3–2008.…”