Assessment of early onset surface damage from accelerated disinfection protocol
The objective of this study was to evaluate the extent and potential mechanisms of early onset surface damage from simulated wiping typical of six-months of routine disinfection and to assess the subsequent microbial risk of surfaces damaged by disinfectants.
Eight common material surfaces were exposed to three disinfectants and a neutral cleaner (neutral cleaner, quaternary ammonium, hydrogen peroxide, sodium hypochlorite) in accelerated aging tests to simulate a long-term disinfection routine. Materials were also immersed in dilute and concentrated chemical solutions to induce surface damage. Surfaces were chemically and physically characterized to determine extent of surface damage. Bactericidal efficacy testing was performed on the Quat-based disinfectant using a modified version of EPA standard operating procedure MB-25-02.
The wiping protocol increased surface roughness for some material surfaces due to mechanical abrasion of the wiping cloth. The increased roughness did not correlate with changes in bactericidal efficacy. Chemical damage was observed for some surface-disinfectant combinations. The greatest observed effects from disinfectant exposure was in changes in wettability or water contact angle.
Early onset surface damage was observed in chemical and physical characterization methods. These high-throughput material measurement methods were effective at assessing nanoscale disinfectant-surface compatibility which may go undetected though routine macroscale testing.
KeywordsSurface damage Roughness Contact angle Disinfectant Material testing
Acrylonitrile Butadiene Styrene
Atomic force microscopy
Ethylene Propylene Diene Monomer (M-class) rubber
Fourier transform infrared
High density polyethylene
Low density polyethylene
Quaternary Ammonium Compounds
X-ray photoelectron spectra
Environmental cleaning practices are key to preventing the transmission of healthcare-associated infections (HAIs), which resulted in ~ 75,000 deaths in the United States in 2011 . Surface-applied disinfectants are frequently used in environmental cleaning as part of the regular hygiene plan. The high-frequency of disinfectant products coming into contact with a wide range of surfaces has the potential to induce incremental damage through each exposure. The risk of damage to the surface is subject to several influences. The age of the surface, exposure time, chemical composition of the disinfectant, and method of disinfectant application all contribute to potential surface damage . The CDC’s Guidelines for Disinfection and Sterilization in Healthcare Facilities lists the shortcomings of various disinfection chemicals, including what kinds of surfaces they can damage .
An article by Spaulding in 1964 reviewed alcohol as a disinfectant and showed that alcohol has been known to damage certain materials . Likewise, disinfectant-induced corrosion of stainless steel has been reported where the damage is undetectable to the naked eye . Although small, this mild degree of surface damage can provide a place for bacteria to inhabit and grow. Repeated use of a disinfectant on a damaged surface will only exacerbate the damage and create a wider berth for bacteria to inhabit . Although it has been known for some time that repeated exposure of a surface to a disinfectant can cause surface damage, the effect on disinfectant efficacy has not been quantified. The objective of this study was to evaluate the extent and potential mechanisms of early onset surface damage from simulated wiping typical of six-months of routine disinfection and to perform a limited assessment of the subsequent microbial risk of surfaces damaged by disinfectants. We hypothesized that subtle changes in the surface chemistry or morphology, as a result of disinfection-induced damage will create potential micro-environments where bacterial pathogens can persist.
Surface damage characterization
Summary of materials with hardness and water absorption; data provided by manufacturer
Hardness (Hardness rating)
Durometer 60D (Medium)
Rockwell R100 (Hard)
Durometer 40A (Medium soft)
Durometer 40D (Medium soft)
Rockwell M100 (Extra hard)
Rockwell R120 (Hard)
Summary of four solutions with product names and dilution ratio
Diversey Virex II 256
Hydrogen peroxide disinfectant
Diversey Oxivir Five 16 concentrate
A conventional goniometer was used to measure contact angles. A sessile drop of 4 μL was supplied to measure contact angle between the sample and the droplet. The samples were also characterized by Fourier transform infrared (FTIR) spectroscopy in order to identify bonding changes before and after wiping and immersing. Samples were weighed before and after immersion tests to determine water absorption. Atomic Force Microscopy (AFM) was utilized to obtain the topography of damaged surfaces in a tapping mode of operation. Surface topography was carried out with measuring surface roughness (Rq). X-ray photoelectron spectra (XPS) were obtained using Kratos Axis Ultra DLD spectrometers with Al Kα radiation (hν = 1486.58 eV).
Bactericidal efficacy testing
Bactericidal efficacy testing was only performed on the diluted Quat disinfectant using a modified version of EPA standard operating procedure MB-25-02 [EPA]. Briefly, bacterial culture was mixed with a soil load (yeast, mucin, and BSA) and inoculated onto 1“× 1” coupons of the polycarbonate, low-density polyethylene, and Formica materials. The coupons were desiccated for 1 h to adhere the bacteria to the surface. The disinfectant was then applied to the coupons and left to sit for the label contact time. After the contact time was reached, 10 mL of neutralizing buffer was added, and the coupon was vortexed in the neutralizing buffer. The solution was vacuum-filtered onto a filter membrane to recover any bacteria that were left. The membrane filter was plated onto TSA for 24–48 h. at 37 °C, and colonies were counted. This procedure was repeated for the treated surfaces and undamaged samples (which established a baseline of disinfectant efficacy).
The Quat-based disinfectant used was Virex II 256. The concentrated disinfectant was diluted at 1:256 using hard water, following EPA MB-25-02 . The disinfectant label contact time was 10 min, and five biological replicates were done for each surface-disinfectant combination. The bacteria tested was Staphylococcus aureus (ATCC #6538), the standard test microbe used in EPA MB-25-02 .
Statistical Analysis Software (SAS), version 9.4, was used to perform analysis of the data. All data were transformed to log10 reduction values for analysis. One-way ANOVA with Tukey Honest Significant Difference (HSD) test was used to determine if differences in disinfectant efficacy existed between the three surface treatments (α = 0.05).
Summarized wiping and immersing test results with full strength and diluted solutions on the six polymers, steel, and glass
Roughness values from the AFM results. Scan sizes of the LDPE and PC images are 100 μm, and the Formica-like surface images are 10 μm
Mechanical damage characterization
In order to characterize microstructure, optical microscopy was initially utilized to analyze overall surface damages on treated surfaces because it is expedient and does not require special sample preparation. Stress whitening was observed at high magnification of optical microscopy, especially on wiped HDPE and wiped LDPE. Stress whitening is a general feature of mechanical surface damage induced by tensile deformation on various polymeric materials and is aesthetically undesirable [6, 7]. Since LDPE has a lower scratch resistance than HDPE, the LDPE showed more scratching during the wiping process. Optical images of HDPE and LDPE were helpful for detecting mechanical damage, while at the microscale chemical damage was hardly observed. In contrast, optical images of EPDM showed a significant chemical effect since the degradation of EPDM can take place in specific chemical environments, as when the disinfectant contains hydrocarbons, hypochlorite, or peroxide . Regarding Formica, this surface seemed to be vulnerable to mechanical impact from wiping disinfection, especially with full-strength disinfectant. This result occurred because full strength disinfectant leaves a residue which evaporates with difficulty, while diluted disinfectant evaporates quickly. Furthermore, since the Formica surface can absorb solution into its laminated layers, the residue of full-strength disinfectant can act more aggressively. Therefore, the repeated wiping of its surface soaked with full strength disinfectant could easily result in mechanical damage. With respect to PC, it has a high impact strength but relatively low scratch resistance . Since PC is transparent it is largely used on clear, see-through surfaces. Fortunately, the mechanical damaging on PC was not aggressive enough to affect the macroscopic transparency, which did not significantly differ from the effects of various concentrations of disinfectant. However, it is noteworthy that even after 4 weeks, when diluted Quat disinfectant was utilized as an immersing solution, immersed PC created a sticky surface which was difficult to remove when rinsed with DI water and was more excessive than the residues deposited on other surfaces from the disinfectant solutions.
Since AFM is able to measure the length and depth of surface damages with a surface profile, it could be a powerful quantitative method tool for surface damage characterization. Despite the use of gentle textured Kimtech wipes, wiped LDPE showed various sizes of scratches on the surface, including one very deep trench, a scratch with a depth of 925 nm as shown in Fig. 2(b). Important to note, bacteria could grow in this space since the sizes of common bacteria are approximately 0.5-1 μm . Furthermore, the scratch with built-up side ridges could lower cleanability: frequent wiping of a ductile surface could produce scratches capable of retaining bacteria. Even though wiping PC also creates a scratched surface, the increased roughness was only a few nanometers, which would not be large enough to allow bacterial growth. From the AFM images of Formica, when the Formica sample was treated with disinfectant, the compressed cellulose fibers that absorbed the solution emerged as small particles on the immersed surface as shown in Fig. 2(i). Judging from the optical images, significant mechanical damage appeared on the Formica surface, however, the AFM results also showed that at the nanoscale, the immersing process resulted in a chemically changed Formica surface.
Chemical damage characterization
Some polymers can absorb small molecules, such as water molecules, as shown in Table 1. Thus, absorption of solutions could be a major chemical impact when samples were immersed in disinfectants [11, 12]. In particular, it is well known that ABS has low chemical resistance to oxidizing agents, which are available to break up the ABS chains . The FTIR results of immersed ABS show a modified IR spectrum with decreased intensities when full strength hydrogen peroxide disinfectant was utilized. These findings may indicate a partial scission of bonds in the ABS, causing decreases in chemical bonds. Aqueous hydrogen peroxide can be dissociated to a free radical, a strong oxidizing agent that can damage substrates . Thus, the higher the concentration of hydrogen peroxide disinfectant, the more aggressive the solution can be on polymer surfaces. Looking at Table 3, the Formica-like surface treated with full strength solutions is also marked as “changed”. Since the Formica surface has a laminated structure, it was able to adsorb solutions physically, which demonstrated a marked change due to its dark surface color. For the immersed PC in diluted Quat disinfectant, sticky residues that were difficult to remove were formed, but the FTIR did not show any notable changes. Since the ATR-FTIR penetration depth is 2 μm , the measurement is not sensitive to the outermost surface of the material. Thus, even though FTIR did not show any changes, it is possible that nanometer-scaled damage occurred on the surface; the damaged PC surface chemistry was measured using XPS.
Regarding the results of XPS, the double bonds that were opened to make covalent bonds with nitrogen from the diluted Quat disinfectant could have precipitated the decreased ratio of C=O. Binding energy also provided both elemental and chemical information. The measured C-O and C=O bonds were slightly shifted to a higher binding energy, thus, it is possible that covalent bonds with nitrogen adsorbed from the diluted Quat disinfectant . Additionally, the ratios of carbon single bonds with hydrogen which is the number 2 carbon in formula increased when the ratio of C=O bonds was significantly decreased. It is also noticeable that no sticky residue occurred with the use of full strength Quat disinfectant. This result indicates that the diluent (water) likely plays a significant role in enabling the specific degradation mechanism when Quat disinfectant and PC are combined and that the residue on the dilute Quat-PC surface is not simply material deposited from the disinfectant . Subsequent XPS data confirmed chemical changes at the PC surface .
The EPA testing method used in this study determined that there was not a significant difference in bactericidal efficacy between undamaged, wiped, and immersed samples. This might be because even undamaged surfaces already had a lot of scratches or the scratches might not have been significantly different to provide protection from disinfection in one cased but not the other. Although LDPE have been observed as mechanically susceptible surfaces from microstructure characterization, there might not be measurable differences from those in the bactericidal efficacy test. The Formica surface also originally had a wavy and bumpy texture, thus, the mechanical damages from the disinfectant process might not have affected the bactericidal efficacy among the undamaged, wiped, and immersed Formica surfaces. Regarding the PC, while PC surface was chemically damaged from the immersing process, it might not be comparable to differentiating disinfectant efficacy between undamaged and immersed PC surfaces. Therefore, the EPA testing method used in this study may not be sensitive enough to detect the differences in disinfectant efficacy due to surface damage. We feel that further study is warranted with respect to disinfectant efficacy of lightly mechanically damaged surfaces as observed from the gentle wiping protocol in this study to better understand the critical threshold of surface damage which can result in loss of bactericidal efficacy.
Surfaces which experience a high-frequency of exposure to disinfectant chemicals may be at additional risk of critical surface damage that renders the surface more challenging to disinfect. Chemical compatibility tests and other screening protocols may overlook the effects of long-term exposure and may otherwise be insufficiently sensitive to changes at the outermost interface material. The surface characterization of eight surfaces exposed to four different disinfectants was used to assess the sensitivity of detection methods for early onset surface damage. The surfaces tested were lightly damaged from a test protocol simulating six-months of routine disinfection. As such, widespread macroscopic damage was not observed. Although full strength disinfectants are not usually utilized in practice, the test was able to demonstrate chemical resistance under an aggressive condition. Some chemical damage was detected using water contact angle and XPS, whereas more conventional FTIR spectroscopy did not detect significant chemical changes. The discrepancy here is attributed to the surface sensitivity of the respective techniques. Most treated surfaces showed no significant chemical damage for any disinfectant exposure (including the concentrated disinfectants under immersed conditions), this further emphasizes the impact of mechanical abrasion as a key source of critical surface damage. Bactericidal efficacy of Virex II 256 (Quat-based) was assessed for select surfaces which exhibited moderate surface damage. However, the EPA testing method used in this study did not detect significant differences in disinfectant efficacy due to modest surface damage. Further study is warranted for surfaces that have experienced more aggressive surface damage, possibly from real in-service material samples, to determine a critical defect population necessary to alter bactericidal efficacy.
The authors thank Kay Bixler and Xiaobao Li for their technical input on the research design and experimental methods.
This work was supported by Diversey Inc., Charlotte, NC, USA.
Availability of data and materials
All data generated or analyzed during this study included in this published article.
HJ performed the disinfectant processes, mechanical and chemical characterization, and wrote the manuscript. AW performed bactericidal efficacy testing and was a contributor in writing and editing the manuscript. PT provided testing materials, industry experience, and was a contributor in writing and editing the manuscript. HO and JH served as the principle investigator for the study and was a contributor in writing and editing the manuscript. All authors read and approved the final manuscript.
Ethics approval and consent to participate
Consent for publication
The authors declare that they have no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
- 2.Truscott W. Researching the right disinfectant for your Facility : without damaging instruments or surfaces; 2017.Google Scholar
- 3.Rutala WA, Weber DJ, HICPAC HICPAC. Guideline for disinfection and sterilization in healthcare facilities. Cent Dis Control Prot. 2017;161. https://www.cdc.gov/infectioncontrol/guidelines/environmental/.
- 5.EPA. “Epa Sop Mb-25-02,” … I. Pomerantz (Environmental Prot. Agency, Off); 2012. p. 10–7.Google Scholar
- 6.Dasari A, Duncan SJ, Misra RDK. "Micro- and nano-scale deformation processes during scratch damage in high density polyethylene," Mater Sci Technol. 2003;19(2):239–43.Google Scholar
- 15.Chem A, Chemistry TA, Academy H, Chemistry A, H B, Chemistry A. FTIR-ATR-spectroscopic analysis of Bis-crown ether based PVC-membranes; 1988. p. 448–53.Google Scholar
- 18.Linda DTG, Sawyer C. Polymer Microscopy. 2nd edi ed. London: Chapman and Hall; 1996.Google Scholar
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.