How reliable are test results from 17 laboratories on the basis of EN 1500 for a hand rub based on 80% (w/w)?

INTRODUCTION

A ring trial organized by the Association of Applied Hygiene (VAH) on the bactericidal efficacy of an ethanol-based hand rub was carried out in 17 laboratories according to EN 1500 with the aim of describing the variability of test results and fulfilment of the methodological acceptance criteria.

METHOD

As a test product, a hand rub based on 80% ethanol (w/w) was tested in comparison with the reference alcohol (60% iso-propanol, v/v) in a crossover design. After pre-washing and contamination following the norm, hands were treated either with the reference alcohol (2 × 3 mL for 2 × 30 s) or the test product (3 mL in 30 s). Post-decontamination values were determined immediately after the rub-in period. Validated neutralizers were used. The arithmetic means of all individual log10 pre-values, post-values and reduction values were calculated per laboratory. Non-inferiority was assumed when the Hodges-Lehmann 97.5% confidence limit was <0.6 in comparison with the reference. A z-score was calculated to determine the laboratory performance.

RESULTS

Two laboratories did not meet the acceptance criteria and were excluded from the analysis. The bactericidal efficacy of the test product was non-inferior to the reference product in four laboratories and not non-inferior in 11 laboratories. The z-score for the Hodges-Lehmann 97.5% confidence limit indicated a satisfactory performance in all laboratories.

CONCLUSION

We consider the EN 1500 test method to be robust in terms of the variability of test results. For products of borderline efficacy, the evaluation should be based on more than one test.

Evolving the EN 1500 test method for alcohol-based hand rub closer to clinical reality by reducing the organic load on hands and enabling product to be applied to dry hands

BACKGROUND

The methods currently used in Europe and North America to evaluate the bactericidal efficacy of hand hygiene products have some limitations, e.g., in the selection of test organisms or the method of contamination, and none of the methods allows prediction of actual clinical efficacy. WHO has therefore proposed to develop methods that better reflect typical clinical reality.

METHODS

In a first experiment, we investigated two contamination methods (immersion according to EN 1500 and low-volume according to ASTM E2755) with the EN 1500 test organism Escherichia coli and using 60% v/v iso-propanol. The second experiment was for comparison of the two contamination methods with Enterococcus faecalis. Finally, the two test organisms were compared using the low-volume contamination method. Data within each experiment was statistically compared using the Wilcoxon test for paired samples and data from all experiments were combined and fit to linear mixed effects models.

RESULTS

Mixed-effects analysis confirmed that the test organism and contamination method both impacted the pre-values and all three of these were factors that influenced log₁₀ reductions. Higher pre-values resulted in significantly higher log₁₀ reductions, immersion contributed to significantly higher log₁₀ reductions, and E. coli affected significantly lower log₁₀ reductions.

CONCLUSION

An efficacy evaluation against E. faecalis with a low-volume contamination method could be considered as an alternative to the EN 1500 standard. This could help improve the clinical relevance of the test method with including a Gram-positive organism and reducing soil load which allows a product application closer to reality.

Failure of sodium hypochlorite to meet the EN 1500 efficacy requirement for hygienic hand disinfection

This study evaluated the bactericidal efficacy of two alternative hand antiseptics, based on sodium hypochlorite or sodium hypochlorite and hypochlorous acid, compared with isopropanol on the hands of volunteers artificially contaminated with Escherichia coli using EN 1500. The reference alcohol was applied according to the norm, and the study formulations were used as in common practice (3 mL for 30 s). The products showed mean log₁₀ reductions of 1.63 and 1.89, both of which were inferior to the reference treatment (4.78). Due to the failure to achieve sufficient bactericidal efficacy within 30 s, sodium hypochlorite (0.05-0.06%) should not be considered for hand disinfection.

Bactericidal efficacy of two modified WHO-recommended alcohol-based hand rubs using two types of rub-in techniques for 15 s

We evaluated the bactericidal efficacy of two modified WHO-recommended alcohol-based hand rubs (3 mL) after a 15-s rubbing period using two different rub-in techniques (three vs six steps). The formulation based on 80% w/w ethanol and 0.5% v/v glycerol (modified WHO I) showed a mean log₁₀-reduction of 3.63 ± 0.87 (six steps) and 3.80 ± 0.71 (three steps) which was inferior to the reference treatment (4.27 ± 0.98; six steps). The efficacy of the formulation based on 75% w/w isopropanol and 0.5% v/v glycerol (modified WHO II) was not inferior to the reference treatment for either rub-in technique.

Handrubbing with sprayed alcohol-based hand rub: an alternative method for effective hand hygiene

BACKGROUND

Hand hygiene is crucial in infection prevention and control. It is unclear whether sprayed alcohol-based hand rub (ABHR) is non-inferior to the World Health Organization (WHO)-recommended method of handrubbing with poured ABHR.

AIM

To test whether sprayed ABHR can be an alternative (non-inferior) method for effective hand hygiene with/without handrubbing.

METHODS

A laboratory experiment was conducted with ABHR (isopropanol 60% v/v) according to European Norm 1500. Hand hygiene was performed by: (1) handrubbing with ABHR poured on to the palm of the hand; (2) handrubbing with sprayed ABHR; and (3) applying sprayed ABHR to hands without handrubbing. Hands were contaminated with Escherichia coli ATCC 10536, followed by hand hygiene and microbiological sampling. A generalized linear mixed model with a random intercept per subject was used to analyse the reduction in bacterial count following hand hygiene.

FINDINGS

In total, 19 healthcare workers participated in the study. Handrubbing with sprayed ABHR was non-inferior [margin log₁₀ 0.6 colony-forming units (cfu)/mL] to the WHO-recommended method of handrubbing with poured ABHR; bacterial count reductions were log₁₀ 3.66 cfu/mL [95% confidence interval (CI) 1.68-5.64] and log₁₀ 3.46 cfu/mL (95% CI 1.27-5.65), respectively. Conversely, non-inferiority was not found for sprayed ABHR without handrubbing [bacterial count reduction log₁₀ 2.76 cfu/mL (95% CI 1.65-3.87)].

CONCLUSION

Handrubbing with sprayed ABHR was non-inferior to handrubbing with ABHR poured on to the palm of the hand to reduce bacterial counts on hands under experimental conditions. Handrubbing with sprayed ABHR may be an acceptable alternative hand hygiene method pending assessment in other settings and for other pathogens.

How long is enough? Identification of product dry-time as a primary driver of alcohol-based hand rub efficacy

Background

The World Health Organization has called for the development of improved methodologies to evaluate alcohol-based handrub (ABHR) efficacy, including evaluation at “short application times and volumes that reflect actual use in healthcare facilities”. The objective of this study was to investigate variables influencing ABHR efficacy, under test conditions reflective of clinical use.

Methods

The test product (60% V/V 2-propanol) was evaluated according to a modified EN 1500 methodology, where application volumes of 1 mL, 2 mL, and 3 mL were rubbed until dry. Statistical analyses were performed to investigate the relative influences of product volume, hand size, and product dry-time on efficacy, and hand size and hand contamination on product dry-time.

Results

Mean log₁₀ reduction factors (SD) were 1.99 (0.66), 2.96 (0.84) and 3.28 (0.96); and mean dry-times (SD) were 24 s (7 s), 50 s (14 s), and 67 s (20 s) at application volumes of 1 mL, 2 mL, and 3 mL, respectively (p ≤ 0.030). When data were examined at the individual volunteer level, there was a statistically significant correlation between dry-time and log reduction factor (p < 0.0001), independent of application volume. There was also a statistically significant correlation between hand surface area and dry-times (p = 0.047), but no correlation between hand surface area and efficacy (p = 0.698).

Conclusions

When keeping other variables such as alcohol type and concentration constant, product dry-time appears to be the primary driver of ABHR efficacy suggesting that dosing should be customized to each individual and focus on achieving a product dry-time delivering adequate efficacy.

Effect of hand lotion on the effectiveness of hygienic hand antisepsis: Implications for practicing hand hygiene

BACKGROUND

Skin protection products should be used after washing hands with soap, during breaks, after work, and during leisure time. Aside from their beneficial effects, skin care products may also interact with alcohol-based hand disinfectants by reducing their efficacy. The aim of this study was to investigate the effect of a hand lotion on the effectiveness of hygienic hand antisepsis using an alcohol-based handrub.

METHODS

The effect of a protective hand lotion against an isopropyl alcohol-based handrub was investigated in 20 healthy volunteers according to the European standard test procedure EN 1500 in the following combinations: handwashing and application of hand lotion, only application of hand lotion, and no washing and no hand lotion (control), each for 5 minutes or 1 hour before hand antisepsis. The difference in microbiologic before-and-after values were expressed as log reduction factor.

RESULTS

The effectiveness of hand antisepsis was not significantly affected in any of the groups using the tested hand lotion.

CONCLUSIONS

Hand antisepsis may be delayed for 5 minutes after hand lotion application. Shorter time intervals might be possible but were not tested.

Dose considerations for alcohol-based hand rubs

BACKGROUND

Manufacturers' recommended dosages for alcohol-based hand rubs are typically determined by measuring product efficacy using a model protocol such as EN 1500; however, anecdotal reports and informal observation suggests that in many cases users self-titrate to much lower doses in real-world application.

AIM

To examine the interdependence of alcohol-based hand-rub volume on in-vivo efficacy using the EN 1500 standard test method, on drying time on users' hands, and on their perceptions of acceptability.

METHODS

Three formulations were studied using EN 1500 and a modification of this method. The modification used volumes ranging from 0.5 to 3.0 mL and 30 s application. Drying times were recorded and user acceptability was established using a three-point scale (too long, OK, or too short). Dying times were analysed in relation to hand surface area.

FINDINGS

The drying time for all three products increased as a function of volume. The drying time displayed a positive association with volume and a negative association with hand surface area. The optimum volume for user acceptability was between 1.5 and 2 mL, yielding a drying time of between 20 and 30 s.

CONCLUSION

Whereas EN 1500 is appropriate for establishing the efficacy of a hygienic hand-rub formulation compared to a benchmark, it does not reflect actual in-use conditions or the likely clinical effectiveness of the product. In particular, it fails to address the need to optimize the volume of application and user acceptability of the product.

Efficacy of hand rubs with a low alcohol concentration listed as effective by a national hospital hygiene society in Europe

Background

Some national hospital hygiene societies in Europe such as the French society for hospital hygiene (SFHH) have positive lists of disinfectants. Few hand disinfectants with a rather low concentration of ethanol are listed by one society as effective for hygienic hand disinfection with 3 mL in 30 s including a virucidal activity in 30 s or 60 s, but published data allow having doubts. We have therefore evaluated the efficacy of three commonly used hand disinfectants according to EN 1500 and EN 14476.

Methods

Products 1 (Aniosgel 85 NPC) and 2 (Aniosrub 85 NPC) were based on 70% ethanol, product 3 (ClinoGel derma+) on 60% ethanol and 15% isopropanol (all w/w). They were tested in 3 laboratories according to EN 1500. Three mL were applied for 30 s and compared to the reference treatment of 2 × 3 mL applications of isopropanol 60% (v/v), on hands artificially contaminated with Escherichia coli. Each laboratory used a cross-over design against the reference alcohol with 15 or 20 volunteers. The virucidal activity of the products was evaluated (EN 14476) in one laboratory against adenovirus and poliovirus in different concentrations (80%, 90%, 97%), with different organic loads (none; clean conditions; phosphate-buffered saline) for up to 3 min.

Results

Product 1 revealed a mean log₁₀-reduction of 3.87 ± 0.79 (laboratory 1) and 4.38 ± 0.87 (laboratory 2) which was significantly lower compared to the reference procedure (4.62 ± 0.89 and 5.00 ± 0.87). In laboratory 3 product 1 was inferior to the reference disinfection (4.06 ± 0.86 versus 4.99 ± 0.90). Product 2 revealed similar results. Product 3 fulfilled the requirements in one laboratory but failed in the two other. None of the three products was able to reduce viral infectivity of both adenovirus and poliovirus by 4 log₁₀ steps in 3 min according to EN 14476.

Conclusions

Efficacy data mentioned in a positive list published by a society for hospital hygiene should still be regarded with caution if they quite obviously contradict published data on the same or similar products.