Evaluating Low-Level Disinfection of Smartphones Using Disinfectant Wipes Under Laboratory-Simulated Conditions

Yulia Chaikin, Tanaya Meaders, Nataliya Marchenko

Sparrow Acoustics Inc., 95 Water Street, St. John’s, Newfoundland and Labrador, A1C 5W2, Canada

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Abstract

Background: Smartphones are now widely used in clinical settings for communication, documentation, and even diagnostic procedures such as digital auscultation. However, their frequent handling makes them potential carriers of microorganisms. Simple and effective cleaning methods are therefore essential to prevent the spread of healthcare-associated infections.

Methods: This study evaluated the efficacy of disinfectant wipes in reducing microbial contamination on mobile device surfaces used in clinical practice. Three commercially available smartphones were experimentally contaminated with bacterial suspensions of Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae supplemented with 5% bovine serum. After drying, each surface was wiped with CaviWipes™ containing isopropanol and quaternary ammonium compounds. Samples were then neutralized in Letheen broth, plated, and incubated to determine bacterial survival.

Results: Cleaning with disinfectant wipes completely eliminated all tested bacteria. No viable colonies were detected after treatment, corresponding to reductions greater than six log₁₀ units for each strain. These results confirm full bactericidal activity in accordance with accepted criteria for low-level disinfection of non-critical medical devices.

Conclusions: Regular cleaning of smartphones with disinfectant wipes is a fast, effective, and laboratory-confirmed method for maintaining microbiological safety in clinical use. This practical approach requires no additional equipment and should be incorporated into routine infection prevention practices in healthcare facilities.

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Background

In recent years, the use of mobile devices in healthcare has increased significantly. Initially, they were used mainly for quick calls or message, and later for accessing medical records, calculating medication dosages, and providing educational support^1,2,3. According to published studies, physicians and nurses check their smartphones dozens of times during a typical shift, reflecting their deep integration into clinical routines^4,5,6.

Smartphones have become not only an auxiliary tool but also a component of diagnostic work. They can be used for cardiac and pulmonary auscultation, as well as for recording, storing, and securely transmitting the obtained sounds. This form of digital auscultation facilitates remote patient consultations and initial screening when stationary diagnostic equipment is not available^7,8.

Concerns regarding smartphone hygiene in clinical environments have persisted in parallel with their growing use. The popular belief that phones are “dirtier than a toilet seat” is widespread in the media but lacks scientific confirmation. In practice, the degree of microbial contamination depends not on the device itself but on how regularly it is cleaned. The real threat often comes from traditional medical instruments, most notably, stethoscopes. After even a single examination, the level of bacterial contamination on the stethoscope’s diaphragm and tubing becomes comparable to that found on a physician’s hands⁹. Although official cleaning guidelines have been published by the Centers for Disease Control and Prevention (CDC)¹⁰ and World Health Organization (WHO)¹¹, most clinicians do not follow them: stethoscopes are disinfected in fewer than 20 % of cases between patients and in only 4% in full compliance with CDC protocols¹².

Microbial contamination of smartphones used by healthcare professionals has been confirmed in multiple studies conducted across different countries and clinical departments. Samples collected from phones used by healthcare workers revealed the presence of clinically significant pathogens^13,14,15.

Unlike stethoscopes, which are composed of parts made from various materials (rubber, plastic, metal, etc.) and include joints, bends, and membranes, smartphones feature a smooth, non-porous, and structurally integral design. This configuration eliminates hard-to-reach areas where contaminants could accumulate, making cleaning and disinfection much easier and more effective. Regular cleaning with sanitizing wipes has been shown to reduce microbial contamination by over 99%¹⁶. Smartphone manufacturers, including Apple Inc., officially allow the use of alcohol-based wipes and Clorox disinfecting wipes on external device surfaces¹⁷; these recommendations are consistent with CDC guidelines for low-level disinfection (LLD) disinfection of non-critical medical devices¹⁰.

However, the effectiveness of mobile device disinfection in clinical practice has so far been confirmed by a limited number of controlled studies. This gap served as the basis for our study, which aimed to evaluate the hygienic effectiveness of the standard LLD procedure for smartphones used for digital auscultation. To this end, laboratory testing was conducted to quantitatively assess the reduction in microbial contamination after treatment with disinfectant wipes and to determine whether the result met the regulatory criterion of greater than 6-log₁₀ for non-critical medical devices^10,18,19.

Materials and Methods

Testing Overview

In this study, we evaluated the effectiveness of disinfectant wipes in eliminating bacterial contamination from smartphone surfaces used for digital auscultation. All testing was performed under controlled laboratory conditions that simulated clinical contamination and cleaning procedures.

Test Facility and Regulatory Compliance

All laboratory work was conducted at Nelson Laboratories (Salt Lake City, Utah, USA) under a validated microbiological testing protocol (Nelson Labs Protocol 202502461, Revision 01; Study 1815005-S01). The procedures complied with the U.S. FDA Good Manufacturing Practice (GMP) regulations outlined in 21 CFR Parts 210, 211, and 820. Disinfection was performed using CaviWipes™ (Metrex Research, Romulus, MI, USA), which are pre-saturated with isopropanol and quaternary ammonium compounds.

Guidelines and References

The testing process followed recommendations of the CDC and the U.S. Environmental Protection Agency (EPA) for LLD of non-critical medical devices ^10,18.

Test Articles and Conditions

Three commercially available smartphones (iPhone 16 Pro) were used as test articles. This device was selected because it has the smooth, non-porous glass-metal surfaces typical of modern smartphones across major manufacturers. The device name is reported solely for methodological transparency and does not influence or limit the applicability of the findings.

To ensure consistent sampling, each phone was divided into four designated areas: the screen, back panel, bottom edge, and control buttons. To reproduce clinical contamination, 0.2 mL of a bacterial suspension supplemented with 5% bovine serum was applied to each area using a syringe. In total, 0.8 mL of inoculum was applied to each device (0.2 mL × four areas). Although this represents a greater liquid volume than typically encountered during routine smartphone use, it was intentionally selected to create a uniform, worst-case contamination load. This approach ensured consistent distribution of microorganisms across all surfaces and enabled a rigorous assessment of disinfection efficacy under high-burden laboratory conditions. The inoculum was allowed to air-dry at room temperature for approximately 50 minutes for Escherichia coli and Staphylococcus aureus or 52 minutes for Pseudomonas aeruginosa and Klebsiella pneumoniae.

The bacterial strains selected for evaluation were Staphylococcus aureus (ATCC 6538), Pseudomonas aeruginosa (ATCC 15442), Escherichia coli (ATCC 8739), and Klebsiella pneumoniae (ATCC 13883). Letheen broth (LETH) was used as a neutralizing medium. Recovered samples were plated on Mannitol Salt Agar (MSA), Eosin Methylene Blue Agar (EMB), MacConkey Agar (MAC), and Cetrimide Agar (CEA). Plates were incubated at 35-39 °C for up to six days before enumeration.

A 3-minute contact time was used in this study because it corresponds to the full wet-contact duration specified on the CaviWipes™ product label for achieving its highest disinfection claim (tuberculocidal activity). Although low-level disinfection (LLD) of non-critical devices can often be achieved with shorter contact times, the 3-minute interval was selected for two reasons: (i) it represents a standardized, regulator-recognized contact time for this wipe formulation in validated laboratory testing, and (ii) maintaining visible wetness for 3 minutes is feasible in a clinical workflow, particularly during routine device turnover between patients. Using the longest validated contact time ensures that the study conditions reflect a conservative, reproducible benchmark consistent with the product’s EPA-registered instructions for use.

Key test parameters are summarized in Table 1.

Table 1: Test materials, bacterial strains, and disinfection parameters

Item	Description
Disinfectant	CaviWipes™ (isopropanol + quaternary ammonium compounds)
Soil load	5% bovine serum in purified water
Environmental conditions	22-24 °C; relative humidity 40-60%
Contact time	3 minutes (surface kept visibly wet)
Replication design	Each bacterial strain tested on three devices in triplicate
Controls	Untreated inoculated surfaces (positive) and sterile coupons (negative)

Experimental Procedure

The cleaning and disinfection process followed the validated Nelson Labs LLD protocol. For clarity and reproducibility, the key steps of the procedure are summarized in Table 2.

Table 2: Summary of procedural steps

Step		Description
1	Preparation	Each smartphone was sterilized before testing to eliminate background contamination, and test areas were marked.
2	Inoculation	A 0.2 mL bacterial suspension (5% bovine serum) was applied to each area and allowed to dry for 50-52 minutes at room temperature.
3	Baseline sampling	Samples were collected from contaminated areas to determine the initial microbial load (N0).
4	Disinfection	Surfaces were wiped with CaviWipes™, maintaining full coverage and visible wetness for three minutes (three wipes per device).
5	Post-cleaning sampling	Samples were taken from the same areas after disinfection to quantify surviving microorganisms (Nt).
6	Neutralization and plating	Samples were transferred into Letheen broth, filtered, and plated on MSA, EMB, MacConkey, Cetrimide. Plates were incubated at 35-39 °C for 1-6 days.
7	Colony counting	Colonies were manually counted. The log-reduction value (LRV) was calculated as LRV = log10 (N0) - log10 (Nt).

Neutralization and Validation Controls

The efficiency of neutralization was verified using Letheen broth, with recovery rates ranging between 93% and 123%, confirming that the neutralizer did not inhibit microbial regrowth. Positive controls yielded baseline counts exceeding 2 × 10⁶ colony-forming unit (CFU) per device, demonstrating adequate contamination and recovery. All quality-control criteria were met, confirming the reproducibility and reliability of the procedure.

Acceptance Criteria and Data Analysis

Based on CDC and EPA standards for non-critical medical devices, LLD is defined by the elimination of vegetative bacteria and other non-spore-forming microorganisms^10,18. In accordance with ASTM E1054-08 and ISO 11737-1:2018, a greater than 6-log₁₀ reduction in bacterial counts was adopted as the benchmark for demonstrating complete bactericidal efficacy under test conditions^20,21. Data were analyzed using GraphPad Prism 10.2 (GraphPad Software, USA) and Microsoft Excel 365. Mean CFU counts and log-reduction values were calculated in triplicate for each organism. Results were classified as “Met” when the greater than 6-log₁₀ reduction threshold was achieved. All testing was conducted under the validated Nelson Labs LLD protocol, in full compliance with the referenced ASTM and ISO standards.

Results and Discussion

Quantitative outcomes and log,sub>10 reductions

Quantitative outcomes and log₁₀ reductions

The laboratory evaluation showed that disinfectant wipes completely removed bacterial contamination from smartphone surfaces inoculated with four clinically significant strains. After cleaning with CaviWipes™, no viable microorganisms were detected on any of the tested devices. All four strains showed log₁₀ reductions greater than 6, with mean values between 6.3 and 7.1, exceeding the benchmark for effective LLD. No growth was observed following neutralization and incubation, confirming full microbial elimination. Table 3 shows the mean bacterial counts before and after cleaning, along with the calculated log₁₀ reductions.

Table 3: Mean bacterial recovery and log₁₀ reduction after cleaning with disinfectant wipes

Microorganism	Mean CFU		Mean log10 reduction (LRV)	Result
	before cleaning (N0)	after cleaning (Nt)
Klebsiella pneumoniae (ATCC 13883)	2.0 × 106	< 1.0 × 100	> 6.3	Pass
Pseudomonas aeruginosa (ATCC 15442)	5.3 × 106	< 1.0 × 100	> 6.7	Pass
Escherichia coli (ATCC 8739)	2.0 × 107	< 2.0 × 100	> 7.0	Pass
Staphylococcus aureus (ATCC 6538)	2.8 × 107	< 2.1 × 100	> 7.1	Pass

[1] Detection limits differ slightly between organisms because of small variations in sample processing steps, including the volume transferred into neutralizing broth and the dilution factor applied before plating. As a result, the minimum detectable CFU values ranged from <1.0 × 10⁰ to <2.1 × 10⁰ CFU per device. These differences reflect methodological constraints rather than differences in disinfection efficacy.

After wiping, bacterial counts on all smartphone surfaces fell below the detection limit (<10 CFU per device), confirming reductions of more than 6 log₁₀ for each organism. The neutralization control confirmed that no residual antimicrobial activity remained, indicating that reductions reflected actual disinfection rather than chemical interference. Negative controls showed no growth, confirming the sterility of the overall experimental setup. The quantitative results of the achieved mean log₁₀ reduction for each bacterial strain are illustrated Figure 1.

Figure 1: Mean log₁₀ reduction (LRV) for each bacterial strain after disinfection

he resulting data (Table 3) show a clear decline from approximately 10⁶ CFU to below the detection threshold (<10 CFU), confirming that the procedure met the established criteria for effective LLD of non-critical medical devices.

Interpretation, limitations, and practical implications

The laboratory evaluation demonstrated that cleaning smartphone surfaces with disinfectant wipes provided effective LLD. For all four tested strains, a reduction in bacterial load of more than 6 log₁₀ was observed; after neutralization and incubation, no colony growth was detected. These results indicate that smartphones are safe for clinical use when disinfected regularly, highlighting the importance of surface hygiene in preventing healthcare-associated infections.

It should be noted that the present study was performed using CaviWipes™ containing isopropanol and quaternary ammonium compounds as a representative example of disinfectant wipes commonly used in clinical settings. Although the test covered only one product, the findings validate the LLD process under CDC-defined conditions and are consistent with the expected performance of comparable disinfectant formulations¹⁰.

Although most previous studies have focused on stethoscopes and other reusable medical tools, smartphones have become an integral component of modern healthcare. They are routinely used for digital auscultation, documentation, and communication, which makes their hygienic maintenance increasingly important. Regular disinfection should therefore be regarded as a standard element of infection-prevention practice in healthcare facilities. The smooth, non-porous surface and solid construction of modern smartphones with minimal gaps promote even distribution of disinfectants and reduce the accumulation of organic material, making the cleaning and disinfection process simpler and more efficient. The use of ready-to-use disinfectant wipes represents a practical and rapid method of routine surface cleaning that does not require specialized equipment. Compared to ultraviolet (UV) or infrared (IR) systems, whose effectiveness depends on precise positioning and exposure duration²², manual disinfection enables immediate removal of organic residues (e.g., sebum, sweat, and skin cells) and laboratory-confirmed bacterial elimination.

Testing was performed under controlled conditions using clinically relevant bacterial cultures representing the most common hospital-associated pathogens and a model organic load. In real clinical settings, surfaces may be exposed to more complex types of microbial contamination, including viral and spore-forming microorganisms. Human factors such as cleaning frequency, technique, or consistency of wiping were also outside the scope of this work. Although the study was designed to simulate clinical contamination, it remains an in-vitro evaluation performed under controlled laboratory conditions. In real practice, wiping technique, pressure, coverage of all surface areas, and immediate re-contamination after device handling introduce significant variability. Additionally, real contamination on smartphones often contains complex multilayered organic residues typical of everyday device use (including biofilm-like deposits of sweat, skin oils, and cosmetic products), which may be more resistant to removal than the standardized 5% bovine serum soil load used in this protocol. Furthermore, although this study used standard ATCC reference strains, it should be acknowledged that some real-world clinical isolates, particularly Staphylococcus aureus and Pseudomonas aeruginosa, may exhibit reduced susceptibility or tolerance to quaternary ammonium compounds (QACs), as reported in recent literature. This does not affect the validity of the present laboratory findings but highlights the importance of ongoing monitoring of disinfectant susceptibility in clinical environments²³.

In practical settings, these parameters are better addressed through standardized guidelines and ongoing quality monitoring in healthcare facilities. Despite these methodological and scope-related limitations, the findings offer strong evidence that regular wiping of device surfaces with appropriate disinfectant products provide reliable LLD and can be recommended as an effective, accessible tool for infection control in routine clinical and public health practice²⁴.

Conclusion

This study demonstrates that regular cleaning of smartphones with appropriate disinfectant products, already available in most healthcare facilities, provides an effective and practical means of preventing bacterial contamination. Routine surface hygiene of mobile devices should be recognized as an essential element of infection prevention, supporting the safe integration of digital technology into clinical practice.

List of Abbreviations

ASTM - American Society for Testing and Materials

ATCC - American Type Culture Collection

CDC - Centers for Disease Control and Prevention

CEA - Cetrimide Agar

CFU - Colony-Forming Units

EMB - Eosin Methylene Blue Agar

EPA - U.S. Environmental Protection Agency

FDA - U.S. Food and Drug Administration

GMP - Good Manufacturing Practice

IR - Infrared

ISO - International Organization for Standardization

LETH - Letheen Broth

LLD - Low-Level Disinfection

LRV - Log Reduction Value

MAC - MacConkey Agar

MSA - Mannitol Salt Agar

UV - Ultraviolet

Conflicts of Interest

All authors are employees of Sparrow Acoustics Inc. The company develops software for digital auscultation but does not manufacture disinfectants, disinfectant wipes, or smartphone devices. Sparrow Acoustics Inc. has no commercial or financial relationship with Metrex Research (manufacturer of CaviWipes™), Apple Inc., or any other disinfectant or smartphone vendors.

The disinfectant product evaluated in this study (CaviWipes™) and the smartphone model used for testing were selected solely to represent commonly available products in clinical practice. No external entity influenced the study design, laboratory procedures, data analysis, interpretation, or the content of the manuscript.

The authors declare no additional conflicts of interest.

Funding

This study was funded by Sparrow Acoustics Inc., which commissioned and paid for the laboratory testing as a standard fee-for-service contract performed independently by Nelson Laboratories (Salt Lake City, UT, USA). Nelson Laboratories functioned as an independent third-party testing facility and was not affiliated with Sparrow Acoustics Inc. Sparrow Acoustics Inc. had no role in the study design, microbiological procedures, data collection, data analysis, or interpretation of results.

The authors alone made the decision to prepare and submit this manuscript for publication.

Authors’ Contributions

Yulia Chaikin conceptualized the study, coordinated project logistics with the independent laboratory, and provided critical feedback on the manuscript.

Tanaya Meaders contributed to the clinical context and provided administrative oversight.

Nataliya Marchenko prepared and edited the manuscript, integrated the findings, and served as the corresponding author.

All authors reviewed and approved the final version of the manuscript and agree to be accountable for all aspects of the work.

Authors’ Information

Yulia Chaikin, PhD - Head of QA/RA, Sparrow Acoustics Inc., Canada

ORCID: 0009-0002-2256-1821

Tanaya Meaders, BSN, RN - Senior Vice President, Medical Business Development, Sparrow Acoustics Inc., Canada

ORCID: 0009-0009-5145-9691

Nataliya Marchenko, MD - Medical Writer, Sparrow Acoustics Inc., Canada, Corresponding Author

ORCID: 0009-0001-9382-7511

Acknowledgments

The authors thank Nelson Laboratories (Salt Lake City, UT, USA) for performing the microbiological testing and providing the validation report.

Data Availability

All relevant data supporting the findings of this study are contained within the article. Additional details derived from the Nelson Laboratories validation report (Study 1815005-S01, 2025) are available from the corresponding author upon reasonable request.

Ethical Approval

Ethical approval was not required, as this study did not involve human participants or animal subjects.

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