- Email: [email protected]
Impact of the amount of hand rub applied in hygienic hand disinfection on the reduction of microbial counts on hands
Journal of Hospital Infection (2010) 74, 212e218
Available online at www.sciencedirect.com
www.elsevierhealth.com/journals/jhin
Impact of the amount of hand rub applied in hygienic hand disinfection on the reduction of microbial counts on hands P. Goroncy-Bermes a,*, T. Koburger b, B. Meyer c a
Schu¨lke & Mayr GmbH, Norderstedt, Germany Hygiene Nord GmbH, Greifswald, Germany c Ecolab Deutschland GmbH, Du¨sseldorf, Germany b
Received 2 March 2009; accepted 18 September 2009 Available online 12 January 2010
KEYWORDS Application volume; EN 1500; Hand rub; Hygienic hand disinfection
Summary Two different hand rubs were tested in order to investigate the minimum volume required for microbicidal efficacy according to the European Norm EN 1500; we also sought to determine whether there is a correlation with hand size. Eight male volunteers with big hands (mean 184 cm 2 ) and eight female volunteers with significantly smaller hands (mean 148 cm2; P < 0.001) participated in our study. Application of 2 mL of both products (P) provided mean log10 reductions significantly smaller than those of the reference disinfectant (R) (product A: P ¼ 3.34, R ¼ 4.00, P ¼ 0.001; product B: P ¼ 3.37, R ¼ 3.75, P ¼ 0.022). Higher volumes (product A: 3 and 4 mL; product B: 2.5, 3 and 4 mL) ensured that the pass criteria of the European Norm (EN) 1500 were fulfilled. For both products log10 reductions increased with increasing product volume until a plateau was reached. For the smaller female hands, this plateau level was reached after applying 3 mL of product A and 2.5 mL of product B. The plateau level on male hands was observed after treating the hands with 4 mL of product A and 3 mL of product B. The increase in product volume also correlated with the decrease in the number of volunteers considering the product volume applied as insufficient. In conclusion, the applied volume for hygienic hand rub should not fall below 3 mL in order to achieve maximum benefit. ª 2009 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved.
* Corresponding author. Address: Schu ¨lke & Mayr GmbH, Research and Development, 22840 Norderstedt, Germany. Tel.: þ49 40 52100552; fax: þ49 40 52100577. E-mail address: [email protected] 0195-6701/$ - see front matter ª 2009 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jhin.2009.09.018
Amount of hand rub and efficacy of hand disinfection
Introduction Hand hygiene is generally regarded as one of the most important measures in the prevention of healthcare-associated infections.1,2 Different types of hand hygiene products and procedures such as hand washing with non-medicated or antimicrobial soap and hand rubbing with alcohol-based hand disinfectants are accepted as appropriate hand hygiene in different countries. However, in high demand situations, such as in most critical care units, or at times of overcrowding or understaffing, promoting hand disinfection with an alcohol-based hand rub solution seems to be the most practical means of improving compliance with hand hygiene guidelines and preventing the transmission of pathogens.1 It requires less time, acts faster, is less likely to irritate hands, and is superior to traditional hand washing or medicated soaps containing antiseptic agents.3e13 The European Norms (EN) 1500 (hygienic hand disinfection) and EN 12791 (surgical hand disinfection) are the state-of-the-art methods in Europe of demonstrating the antimicrobial activity of alcohol-based hand rubs.14,15 Contact time and product amount to be applied are used as parameters to describe the conditions under which a given hand-rub product passes EN 1500 and EN 12791. Recently, Kampf and Ostermeyer reported that the applied amount of reference solution 60% 1-propanol in surgical hand disinfection according to EN 12791 was insignificant as long as the volunteers kept their hands wet for the entire contact time.16 The applied volume considered sufficient was individually assessed by the volunteers. In a different study, 2.4 and 3.6 mL of four marketed hand rubs were tested on contaminated hands, for the reason that alcohol-based hand antiseptics are often tested using 3 or 5 mL per application, but smaller volumes are likely to be applied in clinical practice.17 However, while studies on hand antisepsis with handwash products exist, no study reporting the minimum dose of alcohol-based hand rubs for hygienic hand disinfection has yet been published.18,19 It was therefore the aim of this study to determine the smallest sufficiently effective amount of alcohol-based hand rubs applied to hands according to EN 1500 at a defined contact time of 30 s and whether there is a correlation with the hand size of the volunteers.
Methods Hand-rub preparations Two alcohol-based hand rubs commonly used for hygienic and surgical hand disinfection were
213 evaluated in this study. Product A (Spitacid) was manufactured by Ecolab Deutschland GmbH, Du ¨sseldorf, Germany and is based on 46.0% (w/w) ethanol (96%), 27.0% (w/w) 2-propanol and 1.0% (w/w) benzylalcohol. Product B (desderman N) was manufactured by Schu ¨lke & Mayr GmbH, Norderstedt, Germany and is based on 78.2% (w/w) ethanol (96%) and 0.1% (w/w) 2-biphenylol.
European test method EN 150014 The antimicrobial activity of the hand rubs was assessed with the help of 16 healthy volunteers (eight female, eight male) per experiment. No skin breaks, such as cuts or abrasions, were present on their hands, nor were other skin disorders. Nails were short and clean. The reduction in the release of test organisms from the artificially contaminated hands after application of the hand rubs was determined according to standard procedure. The hand size of each volunteer was determined by measuring the length (from the carpus to the tip of the middle finger) multiplied by width (thumb included).
Study design The study was performed in the laboratories of Hygiene Nord GmbH, Greifswald, Germany. Each volume of the hand rubs was tested in a separate experiment against the reference solution. Instead of a cross-over design, all of the volunteers first used the hand rub that was to be tested and then, in the second step, the reference disinfectant in order to avoid interference of the reference procedure with the test procedure. After a rest period of at least seven days, the next experiment was performed in the same order. The tests were started with the application of the largest amount (4 mL) and finished with the application of the smallest (2 mL). Preparation and application of the contamination fluid The contamination fluid containing Escherichia coli between 2 108 and 2 109 cfu/mL was prepared as described in EN 1500. Hands of the volunteers were immersed in the suspension up to the mid-metacarpals for 5 s with fingers spread apart and were then allowed to dry in the air for 3 min. Hand-rub procedure Immediately after sampling for the prevalues and without recontamination of the hands, the group performed the hand-rub procedures. The
214 reference solution containing 60% 2-propanol (v/v) was placed in each subject’s cupped hands in a modified way based on DGHM (Deutschen Gesellschaft fu ¨r Hygiene und Mikrobiologie) standard methods.20 Instead of placing 3 mL of the reference alcohol into the hands and adding another 3 mL after 30 s for another 30 s contact time as described by EN 1500, 3 mL of the reference solution was applied once for 30 s before volumes of 1e3 mL were applied to the hands for the next 30 s, just enough to keep them sufficiently wet. The two products were applied in several different amounts (product A: 2, 3 and 4 mL; product B: 2, 2.5, 3 and 4 mL) at a contact time of 30 s each to determine the impact of the applied volume on the antimicrobial activity. The disinfectants were distributed on the hands according to the standard hand-rub procedure described in EN 1500. Test validation The requirements for acceptance of test results were thus that all results from at least 12 subjects would be available, the overall mean of the log10 prevalues for reference and test procedures was to be 5.00, and in each procedure, R (reference solution) and P (product), not more than three individual log10 reductions of <3.00 would occur. Calculation of the log10 reduction For both reference and test procedure the log10 counts from right and left hands of each subject were averaged separately for prevalues and postvalues. From the difference between this individually combined log10 prevalue and the log10 postvalue, a log10 reduction was established for each volunteer. Then, the two arithmetic means of all individual log10 reductions were calculated for both the reference and the test procedure. Evaluation of the microbicidal activity Whenever the quality of the data was found acceptable, they were used for the evaluation of the microbicidal activity of the products tested, applying the following pass criteria: e for any product, the mean log10 reduction obtained is not to be significantly smaller than that obtained for the reference 2-propanol; e if the mean log10 reduction of a test product is smaller than that of the reference 2-propanol, then the difference shall be tested for statistical significance; e if the mean log10 reduction is significantly smaller than that obtained with the reference 2-propanol, the test product does not conform to this standard.
P. Goroncy-Bermes et al.
Statistical analysis To test the statistical significance of the difference between the mean log10 reductions of P and R, either for all subjects or separately for the male and female volunteers, the Wilcoxon matched-pairs signed ranks test was used in accordance with EN 1500. Data were presented either as suggested by EN 1500 or as an output of the SPSS software package (version 13.0). That test was also used for the pairwise comparison of the reduction obtained by the test subjects when using different amounts of the products. The critical value for N ¼ 16 is 42 (and 8 for N ¼ 8) at a significance level of P ¼ 0.1 in the directional test. To consider the difference RP as significant, rank sums had to be 42 (16 volunteers), 8 (8 volunteers) or P 0.1, respectively. In contrast to the related random variables R or P, hand size and the mean log10 reduction are independent variables. For each applied amount of the test products, the ManneWhitney U-test was used to assess the significance of the difference of the mean reduction factors obtained with small and large hands.
Results Hand size of the volunteers In this study, the measured average hand size of the eight female volunteers was significantly smaller than that of the eight male volunteers (Table I). The difference was w36 cm2.
Table I Hand size of the participating test subjects and significance of the mean difference Female subjects
Male subjects
Subject no.
Hand size (cm2)
Subject no.
Hand size (cm2)
2 3 6 7 9 12 15 16 Mean Relative SD
134.4 155.7 148.8 150.9 143.5 158.8 144.1 150.9 148.39 5.17
1 4 5 8 10 11 13 14
200.0 207.7 174.4 185.3 177.7 174.2 167.3 182.4 183.63 7.50
Means are significantly different (ManneWhitney U-test: P 0.001; t-test: P 0.001 at a ¼ 0.01). SD: Standard Deviation.
Amount of hand rub and efficacy of hand disinfection
215
Table II Mean log10 reduction after using different amounts of two alcohol-based disinfectants on hands of 16 volunteers compared with a reference solution (60% isopropyl alcohol) Product
Reference solution
Applied volume (mL)
P-value
Mean log10 reduction
Applied volume (mL)
Mean log10 reduction
4.19 3.94 3.34
4e6 4e6 4e6
3.69 3.65 4.00
P > R, P ¼ 0.037 P > R, P ¼ 0.386 P < R, P ¼ 0.001
4.52 4.47 3.99 3.37
4e6 4e6 4e6 4e6
4.00 4.01 3.86 3.75
P > R, P > R, P > R, P < R,
Product A 4 3 2 Product B 4 3 2.5 2
P ¼ 0.011 P ¼ 0.029 P ¼ 0.446 P ¼ 0.022
The significance (P 0.1) of the mean differences of log10 reduction between products (P) and reference solution (R) was assessed by the Wilcoxon matched-pairs signed-ranks test.
Microbicidal activity of the products The results summarised in Table II show that after using 4 mL of both products, the means of microbial reduction were significantly higher than those of the reference solution (product A: P ¼ 0.037; product B: P ¼ 0.011). When using product A, all volunteers assessed the applied volume as sufficient except one with a hand size of 185.3 cm2 (subject no. 8, Table I). After using 3 mL of product A, the mean reduction of the product was higher than the reduction of the reference solution (P > R: 3.94 vs 3.65) but the difference was not significant (P ¼ 0.386). One subject assessed the applied volume of 3 mL as insufficient (No. 8, Table I). In the tests using 3 mL of product B for the disinfection of the hands, the mean log10 reduction was significantly higher compared with the reference solution (P > R: 4.47 vs 4.01, P ¼ 0.029). Again, all volunteers assessed the applied volume as sufficient. The reductions obtained after treating the hands with 2 mL of both products were significantly lower than those of the reference disinfectant (product A: P < R: 3.34 vs 4.00, P ¼ 0.001;
Table III
product B: P < R: 3.37 vs 3.75, P ¼ 0.022). Several female and male volunteers (product A: 7; product B: 4) evaluated the applied volume as not sufficient. The statistical evaluation of log10 reductions obtained with different product volumes shows that the differences in mean log10 reduction between 2.5 and 3 mL and 3 and 4 mL for product B and between 3 and 4 mL for product A were not significant (Table III). All other differences were statistically significant.
Efficacy dependent on hand size The results demonstrate that higher log10 reductions were obtained after treating the bigger hands with any of the disinfectant solutions except when using 2 or 3 mL of product A although these differences were not significant (Table IV). However, no correlation between hand size and microbial reduction could be demonstrated by regression analysis of the full data set of each experiment (P > 0.05). The log10 reduction did not increase after applying 4 instead of 3 mL of product B while it did with product A. Using product A, the plateau
Statistical comparison of antimicrobial reduction obtained with different amounts of test product
Product A (mL)
Product B (mL)
RF of volumex vs RF of volumey
P-value
4.0 (4.19) vs 3.0 (3.94) 4.0 (4.19) vs 2.0 (3.34) 3.0 (3.94) vs 2.0 (3.34)
0.220 0.000 0.009
RF of volumex vs RF of volumey 4.0 4.0 4.0 3.0 3.0 2.5
(4.52) (4.52) (4.52) (4.47) (4.47) (3.99)
vs vs vs vs vs vs
3.0 2.5 2.0 2.5 2.0 2.0
(4.47) (3.99) (3.37) (3.99) (3.37) (3.37)
P-value 0.495 0.091 0.001 0.126 0.001 0.006
RF, reduction factor in parentheses. The significance (P 0.1) of the mean differences in log10 reduction was assessed by the Wilcoxon matched-pairs signed-ranks test.
216
P. Goroncy-Bermes et al.
Table IV Mean log10 reduction after using different amounts of two alcohol-based disinfectants on hands of male and female volunteers compared with the reference solution (60% isopropyl alcohol) Product Applied volume (mL) Product A 4 3 2 Product B 4 3 2.5 2
Reference solution Mean log10 reduction Male
Female
P-value
4.35 3.78 3.19
3.96 4.10 3.49
0.279 0.439 0.221
5.02 5.01 4.02 3.47
4.02 3.92 3.97 3.28
0.052 0.040 0.168 0.244
Applied volume (mL)
Mean log10 reduction Male
Female
P-value
4e6 4e6 4e6
3.78 4.03 4.20
3.61 3.28 3.79
0.253 0.041 0.123
4e6 4e6 4e6 4e6
4.14 4.15 3.82 3.78
3.87 3.88 3.89 3.72
0.229 0.221 0.347 0.313
The significance (P ¼ 0.1) of the mean differences in log10 reduction was assessed by the ManneWhitney U-test.
level was not reached at 3 mL for the hands of the male volunteers. To demonstrate the correlation between applied volume and overall antimicrobial activity more clearly for product B, an additional test was run with 2.5 mL of that disinfectant. The resulting reduction in bacterial density by 4.02 log10 steps (mean value of the male hands) was between those obtained after applying 2 and 3 mL. After disinfecting the female volunteers’ smaller hands with 2.5 mL, it became apparent that the plateau level had already been reached at this volume. It was evident that the microbicidal efficacy was dependent on the correlation between hand size and a given volume of a hand rub applied. Plateau levels, where no further increase in microbial reduction could be achieved by applying higher amounts of product, were reached on smaller hands with lower amounts of product compared to bigger hands.
Discussion The hand disinfection process is terminated at the end of a specified contact time by recovery of surviving test organisms from the hands according to laboratory EN 1500 test conditions. In practice, the applied amount of product used will determine the ‘real life’ contact time of a hand rub. Healthcare workers will rub their hands with the product until hands feel dry again. The application of 3 mL of a hand rub usually leaves hands dry after 30 s, the minimum time recommended for hygienic hand disinfection. Recently, alcohol-based hand disinfectants with contact times shorter than 30 s have been launched for hygienic hand disinfection. That implies that in practice a smaller volume is used in order to have dry hands after a shorter
contact time. In this context it was interesting for us to assess the minimum amount of an alcoholic hand rub that fulfils the pass criteria of EN 1500 at 30 s contact time. Our results clearly demonstrate that at least 2.5e3 mL of alcohol-based hand rub is needed to obtain a micro-organism reduction according to the requirements of EN 1500.14 Application of 2 mL of the products resulted in log10 reductions that were significantly smaller than those of the reference solution. One reason might be that there is no sufficient solution left in the last step (step six) of the rub-in technique described in EN 1500 to disinfect the fingertips of each hand, in contrast to the reference disinfectant. According to the European Norm, sampling of surviving test organisms is performed by rubbing the distal phalanges of the right and left hand separately, including thumbs, for 1 min on two Petri dishes, each containing 10 mL of tryptic soy broth. Other parts of the hands are disregarded. Other parameters such as insufficiently treated areas might also be responsible for less antimicrobial activity of hand rubs. Kampf et al. reported that untreated areas on hands, visualised by a disinfectant solution containing a fluorescent dye, were found following short applications, even though 3 mL of hand rub were applied.21 However, fingertips and palms, the most relevant parts when using hands in healthcare, were often completely covered. Unfortunately, the antimicrobial activity was not evaluated, so it is unknown as to whether there is a correlation with untreated skin areas, defined as a gap of fluorescent dye on the hands. Nevertheless, the authors concluded that high quality hygienic hand disinfection is not possible within 15 s and that a 30 s application time should be recommended for clinical practice. High quality
Amount of hand rub and efficacy of hand disinfection hand disinfection was defined as the absence of large untreated areas and the absence of untreated areas on fingertips and palms. Given the increase in microbial reduction by using increasing amounts of disinfecting solutions, described above, up to a product-dependent plateau, one might expect the microbial reduction to correlate inversely with hand size at a fixed volume. No such correlation could be demonstrated, however. There is considerable variation in the log10 reduction and this may mask any possible correlation between hand size and log10 reduction. It may also be the case that the range of hand sizes is so limited in this study that any correlation may not manifest itself. The correlation could only be demonstrated by analysing average data for the male and female subgroups. In another study, Kampf reported that a 2.4 mL aliquot of a hand-rub product was sufficient to cover both hands in 96.9% of the subjects, as assessed by a technician who recorded ‘yes’ if the product volume was sufficient to completely cover the subject’s hands or ‘no’ if it was not.17 That is in contrast to our findings. Approximately one-third of the volunteers assessed the applied 2.5 mL volume of product B as ‘not sufficient’ although the mean reduction factor was higher than the reduction factor of the reference solution. The application of 3 mL of both products was individually assessed as ‘sufficient’, with one exception. Furthermore, Kampf showed in his study that the application of a higher volume was significantly more effective for some hand rubs tested and that it was also related to a product’s overall concentration of alcohol.17 These results were confirmed by our data. The application of higher volumes of both products increased the reduction of the bacterial count on contaminated hands until the plateau level was reached. Furthermore, it is obvious that both products act differently in killing micro-organisms on account of the different compositions of the hand rubs. Nevertheless, neither product fulfilled the pass criteria of EN 1500 after applying 2 mL but they did fulfil the pass criteria at 2.5 or 3 mL respectively. In most cases it was also observed that a higher reduction in bacterial density was obtained on the male volunteers’ bigger hands. Further investigation is required to find out the reason for this phenomenon. In conclusion, it is reasonable to recommend the application of 3 mL as a minimum dose of an alcoholic hand disinfectant at 30 s contact time provided that it contains a sufficient concentration of active ingredients to fulfil the pass criteria of EN 1500. In practice, the applied amount of product is not precisely measured. As a pragmatic
217 approach, therefore, one might instruct users to apply as much solution as needed to wet the overall surfaces of both hands thoroughly and rub hands to ensure coverage of all areas until they are dry. Conflict of interest statement All authors are employees of the companies as mentioned on the title page. Funding sources The study has been sponsored by Ecolab and Schu ¨lke & Mayr.
References 1. Pittet D, Boyce JM. Hand hygiene and patient care: pursuing the Semmelweis legacy. Lancet Infect Dis 2001:9e20. 2. Jumaa PA. Hand hygiene: simple and complex. Int J Infect Dis 2005;9:3e14. 3. Carro C, Camilleri L, Traore O, et al. An in-use microbiological comparison of two surgical hand disinfection techniques in cardiothoracic surgery: hand rubbing versus hand scrubbing. J Hosp Infect 2007;67:62e66. 4. Girou E, Loyeau S, Gegrand P, Oppein F, Brun-Buisson C. Efficacy of hand rubbing with alcohol based solution versus standard hand washing with antiseptic soap: randomized clinical trial. Br Med J 2002;325:362e365. 5. Kac G, Podglajen I, Gueneret M, Vaupre ´ S, Bissery A, Meyer G. Microbiological evaluation of two hand hygiene procedures achieved by healthcare workers during routine patient care: a randomized study. J Hosp Infect 2005;60: 32e39. 6. Tavolacci MP, Pitrou I, Merle V, Haghighat S, Thillard D, Czernichow P. Surgical hand rubbing compared with surgical hand scrubbing: comparison of efficacy and costs. J Hosp Infect 2006;63:55e59. 7. Kampf G. State-of-the-art hand hygiene in community medicine. Int J Hyg Environ Health 2003;206:465e472. 8. Kampf G, Lo ¨ffler H. Dermatological aspects of successful introduction and continuation of alcohol-based hand rubs for hygienic hand disinfection. J Hosp Infect 2003;55:1e7. 9. Kappes UP, Go ¨ritz N, Wigger-Alberti W, Heinemann C, Elsner P. Tandem application of sodium lauryl sulfate and n-propanol does not lead to enhancement of cumulative skin irritation. Acta Derm Venereol 2001;81:403e405. 10. Larson E, Girard R, Pessoa-Silva CL, Boyce J, Donaldson L, Pittet D. Skin reactions related to hand hygiene and selection of hand hygiene products. Am J Infect Control 2006; 34:627e635. 11. Lo ¨ffler H, Kampf G, Schmermund D, Maibach HI. How irritant is alcohol? Br J Dermatol 2007;157:74e81. 12. Parienti JJ, Thibon P, Heller R, et al. Hand-rubbing with an aqueous alcoholic solution vs traditional hand scrubbing and 30-day surgical site infection rates. J Am Med Assoc 2002; 288:722e727. 13. Rotter ML. Arguments for alcoholic hand disinfection. J Hosp Infect 2001;48(Suppl. A):S4eS8. 14. EN 1500:1997. Chemical disinfectants and antiseptics. Hygienic hand disinfection. Test method and requirement (phase 2, step 2). Brussels: Comite ´ Europe ´en de Normalisation; 1997.
218 15. EN 12791:2005. Chemical disinfectants and antiseptics. Surgical hand disinfection. Test method and requirement (phase 2, step 2). Brussels: Comite ´ Europe ´en de Normalisation; 2005. 16. Kampf G, Ostermeyer C. Influence of applied volume on efficacy of 3-minute surgical reference disinfection method prEN 12791. Appl Environ Microbiol 2004;70:7066e7069. 17. Kampf G. How effective are hand antiseptics for the postcontamination treatment of hands when used as recommended? Am J Infect Control 2008;36:356e360. 18. Aksoy A, Caglayan F, Cakmak M, et al. An investigation of the factors that affect surgical hand disinfection with polyvidone iodine. J Hosp Infect 2005;61:15e19.
P. Goroncy-Bermes et al. 19. Fuls JL, Rodgers ND, Fischler GE, et al. Alternative hand contamination technique to compare the activities of antimicrobial and nonantimicrobial soaps under different test conditions. Appl Environ Microbiol 2008;74:3739e3744. 20. Gebel J, Werner H-P, Kirsch-Altena A, et al. Hygienische Ha ¨ndedesinfektion e praxisnaher Versuch mit Probanden. In: Standardmethoden der DGHM zur Pru¨fung chemischer Desinfektionsverfahren. Wiesbaden: mhp-Verlag; 2001. p. 29e32. 21. Kampf G, Reichel M, Feil Y, Eggerstedt S, Kaulfers PM. Influence of rub-in technique on required application time and hand coverage in hygienic hand disinfection. BMC Infect Dis 2008;8:149e160.
Available online at www.sciencedirect.com
www.elsevierhealth.com/journals/jhin
Impact of the amount of hand rub applied in hygienic hand disinfection on the reduction of microbial counts on hands P. Goroncy-Bermes a,*, T. Koburger b, B. Meyer c a
Schu¨lke & Mayr GmbH, Norderstedt, Germany Hygiene Nord GmbH, Greifswald, Germany c Ecolab Deutschland GmbH, Du¨sseldorf, Germany b
Received 2 March 2009; accepted 18 September 2009 Available online 12 January 2010
KEYWORDS Application volume; EN 1500; Hand rub; Hygienic hand disinfection
Summary Two different hand rubs were tested in order to investigate the minimum volume required for microbicidal efficacy according to the European Norm EN 1500; we also sought to determine whether there is a correlation with hand size. Eight male volunteers with big hands (mean 184 cm 2 ) and eight female volunteers with significantly smaller hands (mean 148 cm2; P < 0.001) participated in our study. Application of 2 mL of both products (P) provided mean log10 reductions significantly smaller than those of the reference disinfectant (R) (product A: P ¼ 3.34, R ¼ 4.00, P ¼ 0.001; product B: P ¼ 3.37, R ¼ 3.75, P ¼ 0.022). Higher volumes (product A: 3 and 4 mL; product B: 2.5, 3 and 4 mL) ensured that the pass criteria of the European Norm (EN) 1500 were fulfilled. For both products log10 reductions increased with increasing product volume until a plateau was reached. For the smaller female hands, this plateau level was reached after applying 3 mL of product A and 2.5 mL of product B. The plateau level on male hands was observed after treating the hands with 4 mL of product A and 3 mL of product B. The increase in product volume also correlated with the decrease in the number of volunteers considering the product volume applied as insufficient. In conclusion, the applied volume for hygienic hand rub should not fall below 3 mL in order to achieve maximum benefit. ª 2009 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved.
* Corresponding author. Address: Schu ¨lke & Mayr GmbH, Research and Development, 22840 Norderstedt, Germany. Tel.: þ49 40 52100552; fax: þ49 40 52100577. E-mail address: [email protected] 0195-6701/$ - see front matter ª 2009 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jhin.2009.09.018
Amount of hand rub and efficacy of hand disinfection
Introduction Hand hygiene is generally regarded as one of the most important measures in the prevention of healthcare-associated infections.1,2 Different types of hand hygiene products and procedures such as hand washing with non-medicated or antimicrobial soap and hand rubbing with alcohol-based hand disinfectants are accepted as appropriate hand hygiene in different countries. However, in high demand situations, such as in most critical care units, or at times of overcrowding or understaffing, promoting hand disinfection with an alcohol-based hand rub solution seems to be the most practical means of improving compliance with hand hygiene guidelines and preventing the transmission of pathogens.1 It requires less time, acts faster, is less likely to irritate hands, and is superior to traditional hand washing or medicated soaps containing antiseptic agents.3e13 The European Norms (EN) 1500 (hygienic hand disinfection) and EN 12791 (surgical hand disinfection) are the state-of-the-art methods in Europe of demonstrating the antimicrobial activity of alcohol-based hand rubs.14,15 Contact time and product amount to be applied are used as parameters to describe the conditions under which a given hand-rub product passes EN 1500 and EN 12791. Recently, Kampf and Ostermeyer reported that the applied amount of reference solution 60% 1-propanol in surgical hand disinfection according to EN 12791 was insignificant as long as the volunteers kept their hands wet for the entire contact time.16 The applied volume considered sufficient was individually assessed by the volunteers. In a different study, 2.4 and 3.6 mL of four marketed hand rubs were tested on contaminated hands, for the reason that alcohol-based hand antiseptics are often tested using 3 or 5 mL per application, but smaller volumes are likely to be applied in clinical practice.17 However, while studies on hand antisepsis with handwash products exist, no study reporting the minimum dose of alcohol-based hand rubs for hygienic hand disinfection has yet been published.18,19 It was therefore the aim of this study to determine the smallest sufficiently effective amount of alcohol-based hand rubs applied to hands according to EN 1500 at a defined contact time of 30 s and whether there is a correlation with the hand size of the volunteers.
Methods Hand-rub preparations Two alcohol-based hand rubs commonly used for hygienic and surgical hand disinfection were
213 evaluated in this study. Product A (Spitacid) was manufactured by Ecolab Deutschland GmbH, Du ¨sseldorf, Germany and is based on 46.0% (w/w) ethanol (96%), 27.0% (w/w) 2-propanol and 1.0% (w/w) benzylalcohol. Product B (desderman N) was manufactured by Schu ¨lke & Mayr GmbH, Norderstedt, Germany and is based on 78.2% (w/w) ethanol (96%) and 0.1% (w/w) 2-biphenylol.
European test method EN 150014 The antimicrobial activity of the hand rubs was assessed with the help of 16 healthy volunteers (eight female, eight male) per experiment. No skin breaks, such as cuts or abrasions, were present on their hands, nor were other skin disorders. Nails were short and clean. The reduction in the release of test organisms from the artificially contaminated hands after application of the hand rubs was determined according to standard procedure. The hand size of each volunteer was determined by measuring the length (from the carpus to the tip of the middle finger) multiplied by width (thumb included).
Study design The study was performed in the laboratories of Hygiene Nord GmbH, Greifswald, Germany. Each volume of the hand rubs was tested in a separate experiment against the reference solution. Instead of a cross-over design, all of the volunteers first used the hand rub that was to be tested and then, in the second step, the reference disinfectant in order to avoid interference of the reference procedure with the test procedure. After a rest period of at least seven days, the next experiment was performed in the same order. The tests were started with the application of the largest amount (4 mL) and finished with the application of the smallest (2 mL). Preparation and application of the contamination fluid The contamination fluid containing Escherichia coli between 2 108 and 2 109 cfu/mL was prepared as described in EN 1500. Hands of the volunteers were immersed in the suspension up to the mid-metacarpals for 5 s with fingers spread apart and were then allowed to dry in the air for 3 min. Hand-rub procedure Immediately after sampling for the prevalues and without recontamination of the hands, the group performed the hand-rub procedures. The
214 reference solution containing 60% 2-propanol (v/v) was placed in each subject’s cupped hands in a modified way based on DGHM (Deutschen Gesellschaft fu ¨r Hygiene und Mikrobiologie) standard methods.20 Instead of placing 3 mL of the reference alcohol into the hands and adding another 3 mL after 30 s for another 30 s contact time as described by EN 1500, 3 mL of the reference solution was applied once for 30 s before volumes of 1e3 mL were applied to the hands for the next 30 s, just enough to keep them sufficiently wet. The two products were applied in several different amounts (product A: 2, 3 and 4 mL; product B: 2, 2.5, 3 and 4 mL) at a contact time of 30 s each to determine the impact of the applied volume on the antimicrobial activity. The disinfectants were distributed on the hands according to the standard hand-rub procedure described in EN 1500. Test validation The requirements for acceptance of test results were thus that all results from at least 12 subjects would be available, the overall mean of the log10 prevalues for reference and test procedures was to be 5.00, and in each procedure, R (reference solution) and P (product), not more than three individual log10 reductions of <3.00 would occur. Calculation of the log10 reduction For both reference and test procedure the log10 counts from right and left hands of each subject were averaged separately for prevalues and postvalues. From the difference between this individually combined log10 prevalue and the log10 postvalue, a log10 reduction was established for each volunteer. Then, the two arithmetic means of all individual log10 reductions were calculated for both the reference and the test procedure. Evaluation of the microbicidal activity Whenever the quality of the data was found acceptable, they were used for the evaluation of the microbicidal activity of the products tested, applying the following pass criteria: e for any product, the mean log10 reduction obtained is not to be significantly smaller than that obtained for the reference 2-propanol; e if the mean log10 reduction of a test product is smaller than that of the reference 2-propanol, then the difference shall be tested for statistical significance; e if the mean log10 reduction is significantly smaller than that obtained with the reference 2-propanol, the test product does not conform to this standard.
P. Goroncy-Bermes et al.
Statistical analysis To test the statistical significance of the difference between the mean log10 reductions of P and R, either for all subjects or separately for the male and female volunteers, the Wilcoxon matched-pairs signed ranks test was used in accordance with EN 1500. Data were presented either as suggested by EN 1500 or as an output of the SPSS software package (version 13.0). That test was also used for the pairwise comparison of the reduction obtained by the test subjects when using different amounts of the products. The critical value for N ¼ 16 is 42 (and 8 for N ¼ 8) at a significance level of P ¼ 0.1 in the directional test. To consider the difference RP as significant, rank sums had to be 42 (16 volunteers), 8 (8 volunteers) or P 0.1, respectively. In contrast to the related random variables R or P, hand size and the mean log10 reduction are independent variables. For each applied amount of the test products, the ManneWhitney U-test was used to assess the significance of the difference of the mean reduction factors obtained with small and large hands.
Results Hand size of the volunteers In this study, the measured average hand size of the eight female volunteers was significantly smaller than that of the eight male volunteers (Table I). The difference was w36 cm2.
Table I Hand size of the participating test subjects and significance of the mean difference Female subjects
Male subjects
Subject no.
Hand size (cm2)
Subject no.
Hand size (cm2)
2 3 6 7 9 12 15 16 Mean Relative SD
134.4 155.7 148.8 150.9 143.5 158.8 144.1 150.9 148.39 5.17
1 4 5 8 10 11 13 14
200.0 207.7 174.4 185.3 177.7 174.2 167.3 182.4 183.63 7.50
Means are significantly different (ManneWhitney U-test: P 0.001; t-test: P 0.001 at a ¼ 0.01). SD: Standard Deviation.
Amount of hand rub and efficacy of hand disinfection
215
Table II Mean log10 reduction after using different amounts of two alcohol-based disinfectants on hands of 16 volunteers compared with a reference solution (60% isopropyl alcohol) Product
Reference solution
Applied volume (mL)
P-value
Mean log10 reduction
Applied volume (mL)
Mean log10 reduction
4.19 3.94 3.34
4e6 4e6 4e6
3.69 3.65 4.00
P > R, P ¼ 0.037 P > R, P ¼ 0.386 P < R, P ¼ 0.001
4.52 4.47 3.99 3.37
4e6 4e6 4e6 4e6
4.00 4.01 3.86 3.75
P > R, P > R, P > R, P < R,
Product A 4 3 2 Product B 4 3 2.5 2
P ¼ 0.011 P ¼ 0.029 P ¼ 0.446 P ¼ 0.022
The significance (P 0.1) of the mean differences of log10 reduction between products (P) and reference solution (R) was assessed by the Wilcoxon matched-pairs signed-ranks test.
Microbicidal activity of the products The results summarised in Table II show that after using 4 mL of both products, the means of microbial reduction were significantly higher than those of the reference solution (product A: P ¼ 0.037; product B: P ¼ 0.011). When using product A, all volunteers assessed the applied volume as sufficient except one with a hand size of 185.3 cm2 (subject no. 8, Table I). After using 3 mL of product A, the mean reduction of the product was higher than the reduction of the reference solution (P > R: 3.94 vs 3.65) but the difference was not significant (P ¼ 0.386). One subject assessed the applied volume of 3 mL as insufficient (No. 8, Table I). In the tests using 3 mL of product B for the disinfection of the hands, the mean log10 reduction was significantly higher compared with the reference solution (P > R: 4.47 vs 4.01, P ¼ 0.029). Again, all volunteers assessed the applied volume as sufficient. The reductions obtained after treating the hands with 2 mL of both products were significantly lower than those of the reference disinfectant (product A: P < R: 3.34 vs 4.00, P ¼ 0.001;
Table III
product B: P < R: 3.37 vs 3.75, P ¼ 0.022). Several female and male volunteers (product A: 7; product B: 4) evaluated the applied volume as not sufficient. The statistical evaluation of log10 reductions obtained with different product volumes shows that the differences in mean log10 reduction between 2.5 and 3 mL and 3 and 4 mL for product B and between 3 and 4 mL for product A were not significant (Table III). All other differences were statistically significant.
Efficacy dependent on hand size The results demonstrate that higher log10 reductions were obtained after treating the bigger hands with any of the disinfectant solutions except when using 2 or 3 mL of product A although these differences were not significant (Table IV). However, no correlation between hand size and microbial reduction could be demonstrated by regression analysis of the full data set of each experiment (P > 0.05). The log10 reduction did not increase after applying 4 instead of 3 mL of product B while it did with product A. Using product A, the plateau
Statistical comparison of antimicrobial reduction obtained with different amounts of test product
Product A (mL)
Product B (mL)
RF of volumex vs RF of volumey
P-value
4.0 (4.19) vs 3.0 (3.94) 4.0 (4.19) vs 2.0 (3.34) 3.0 (3.94) vs 2.0 (3.34)
0.220 0.000 0.009
RF of volumex vs RF of volumey 4.0 4.0 4.0 3.0 3.0 2.5
(4.52) (4.52) (4.52) (4.47) (4.47) (3.99)
vs vs vs vs vs vs
3.0 2.5 2.0 2.5 2.0 2.0
(4.47) (3.99) (3.37) (3.99) (3.37) (3.37)
P-value 0.495 0.091 0.001 0.126 0.001 0.006
RF, reduction factor in parentheses. The significance (P 0.1) of the mean differences in log10 reduction was assessed by the Wilcoxon matched-pairs signed-ranks test.
216
P. Goroncy-Bermes et al.
Table IV Mean log10 reduction after using different amounts of two alcohol-based disinfectants on hands of male and female volunteers compared with the reference solution (60% isopropyl alcohol) Product Applied volume (mL) Product A 4 3 2 Product B 4 3 2.5 2
Reference solution Mean log10 reduction Male
Female
P-value
4.35 3.78 3.19
3.96 4.10 3.49
0.279 0.439 0.221
5.02 5.01 4.02 3.47
4.02 3.92 3.97 3.28
0.052 0.040 0.168 0.244
Applied volume (mL)
Mean log10 reduction Male
Female
P-value
4e6 4e6 4e6
3.78 4.03 4.20
3.61 3.28 3.79
0.253 0.041 0.123
4e6 4e6 4e6 4e6
4.14 4.15 3.82 3.78
3.87 3.88 3.89 3.72
0.229 0.221 0.347 0.313
The significance (P ¼ 0.1) of the mean differences in log10 reduction was assessed by the ManneWhitney U-test.
level was not reached at 3 mL for the hands of the male volunteers. To demonstrate the correlation between applied volume and overall antimicrobial activity more clearly for product B, an additional test was run with 2.5 mL of that disinfectant. The resulting reduction in bacterial density by 4.02 log10 steps (mean value of the male hands) was between those obtained after applying 2 and 3 mL. After disinfecting the female volunteers’ smaller hands with 2.5 mL, it became apparent that the plateau level had already been reached at this volume. It was evident that the microbicidal efficacy was dependent on the correlation between hand size and a given volume of a hand rub applied. Plateau levels, where no further increase in microbial reduction could be achieved by applying higher amounts of product, were reached on smaller hands with lower amounts of product compared to bigger hands.
Discussion The hand disinfection process is terminated at the end of a specified contact time by recovery of surviving test organisms from the hands according to laboratory EN 1500 test conditions. In practice, the applied amount of product used will determine the ‘real life’ contact time of a hand rub. Healthcare workers will rub their hands with the product until hands feel dry again. The application of 3 mL of a hand rub usually leaves hands dry after 30 s, the minimum time recommended for hygienic hand disinfection. Recently, alcohol-based hand disinfectants with contact times shorter than 30 s have been launched for hygienic hand disinfection. That implies that in practice a smaller volume is used in order to have dry hands after a shorter
contact time. In this context it was interesting for us to assess the minimum amount of an alcoholic hand rub that fulfils the pass criteria of EN 1500 at 30 s contact time. Our results clearly demonstrate that at least 2.5e3 mL of alcohol-based hand rub is needed to obtain a micro-organism reduction according to the requirements of EN 1500.14 Application of 2 mL of the products resulted in log10 reductions that were significantly smaller than those of the reference solution. One reason might be that there is no sufficient solution left in the last step (step six) of the rub-in technique described in EN 1500 to disinfect the fingertips of each hand, in contrast to the reference disinfectant. According to the European Norm, sampling of surviving test organisms is performed by rubbing the distal phalanges of the right and left hand separately, including thumbs, for 1 min on two Petri dishes, each containing 10 mL of tryptic soy broth. Other parts of the hands are disregarded. Other parameters such as insufficiently treated areas might also be responsible for less antimicrobial activity of hand rubs. Kampf et al. reported that untreated areas on hands, visualised by a disinfectant solution containing a fluorescent dye, were found following short applications, even though 3 mL of hand rub were applied.21 However, fingertips and palms, the most relevant parts when using hands in healthcare, were often completely covered. Unfortunately, the antimicrobial activity was not evaluated, so it is unknown as to whether there is a correlation with untreated skin areas, defined as a gap of fluorescent dye on the hands. Nevertheless, the authors concluded that high quality hygienic hand disinfection is not possible within 15 s and that a 30 s application time should be recommended for clinical practice. High quality
Amount of hand rub and efficacy of hand disinfection hand disinfection was defined as the absence of large untreated areas and the absence of untreated areas on fingertips and palms. Given the increase in microbial reduction by using increasing amounts of disinfecting solutions, described above, up to a product-dependent plateau, one might expect the microbial reduction to correlate inversely with hand size at a fixed volume. No such correlation could be demonstrated, however. There is considerable variation in the log10 reduction and this may mask any possible correlation between hand size and log10 reduction. It may also be the case that the range of hand sizes is so limited in this study that any correlation may not manifest itself. The correlation could only be demonstrated by analysing average data for the male and female subgroups. In another study, Kampf reported that a 2.4 mL aliquot of a hand-rub product was sufficient to cover both hands in 96.9% of the subjects, as assessed by a technician who recorded ‘yes’ if the product volume was sufficient to completely cover the subject’s hands or ‘no’ if it was not.17 That is in contrast to our findings. Approximately one-third of the volunteers assessed the applied 2.5 mL volume of product B as ‘not sufficient’ although the mean reduction factor was higher than the reduction factor of the reference solution. The application of 3 mL of both products was individually assessed as ‘sufficient’, with one exception. Furthermore, Kampf showed in his study that the application of a higher volume was significantly more effective for some hand rubs tested and that it was also related to a product’s overall concentration of alcohol.17 These results were confirmed by our data. The application of higher volumes of both products increased the reduction of the bacterial count on contaminated hands until the plateau level was reached. Furthermore, it is obvious that both products act differently in killing micro-organisms on account of the different compositions of the hand rubs. Nevertheless, neither product fulfilled the pass criteria of EN 1500 after applying 2 mL but they did fulfil the pass criteria at 2.5 or 3 mL respectively. In most cases it was also observed that a higher reduction in bacterial density was obtained on the male volunteers’ bigger hands. Further investigation is required to find out the reason for this phenomenon. In conclusion, it is reasonable to recommend the application of 3 mL as a minimum dose of an alcoholic hand disinfectant at 30 s contact time provided that it contains a sufficient concentration of active ingredients to fulfil the pass criteria of EN 1500. In practice, the applied amount of product is not precisely measured. As a pragmatic
217 approach, therefore, one might instruct users to apply as much solution as needed to wet the overall surfaces of both hands thoroughly and rub hands to ensure coverage of all areas until they are dry. Conflict of interest statement All authors are employees of the companies as mentioned on the title page. Funding sources The study has been sponsored by Ecolab and Schu ¨lke & Mayr.
References 1. Pittet D, Boyce JM. Hand hygiene and patient care: pursuing the Semmelweis legacy. Lancet Infect Dis 2001:9e20. 2. Jumaa PA. Hand hygiene: simple and complex. Int J Infect Dis 2005;9:3e14. 3. Carro C, Camilleri L, Traore O, et al. An in-use microbiological comparison of two surgical hand disinfection techniques in cardiothoracic surgery: hand rubbing versus hand scrubbing. J Hosp Infect 2007;67:62e66. 4. Girou E, Loyeau S, Gegrand P, Oppein F, Brun-Buisson C. Efficacy of hand rubbing with alcohol based solution versus standard hand washing with antiseptic soap: randomized clinical trial. Br Med J 2002;325:362e365. 5. Kac G, Podglajen I, Gueneret M, Vaupre ´ S, Bissery A, Meyer G. Microbiological evaluation of two hand hygiene procedures achieved by healthcare workers during routine patient care: a randomized study. J Hosp Infect 2005;60: 32e39. 6. Tavolacci MP, Pitrou I, Merle V, Haghighat S, Thillard D, Czernichow P. Surgical hand rubbing compared with surgical hand scrubbing: comparison of efficacy and costs. J Hosp Infect 2006;63:55e59. 7. Kampf G. State-of-the-art hand hygiene in community medicine. Int J Hyg Environ Health 2003;206:465e472. 8. Kampf G, Lo ¨ffler H. Dermatological aspects of successful introduction and continuation of alcohol-based hand rubs for hygienic hand disinfection. J Hosp Infect 2003;55:1e7. 9. Kappes UP, Go ¨ritz N, Wigger-Alberti W, Heinemann C, Elsner P. Tandem application of sodium lauryl sulfate and n-propanol does not lead to enhancement of cumulative skin irritation. Acta Derm Venereol 2001;81:403e405. 10. Larson E, Girard R, Pessoa-Silva CL, Boyce J, Donaldson L, Pittet D. Skin reactions related to hand hygiene and selection of hand hygiene products. Am J Infect Control 2006; 34:627e635. 11. Lo ¨ffler H, Kampf G, Schmermund D, Maibach HI. How irritant is alcohol? Br J Dermatol 2007;157:74e81. 12. Parienti JJ, Thibon P, Heller R, et al. Hand-rubbing with an aqueous alcoholic solution vs traditional hand scrubbing and 30-day surgical site infection rates. J Am Med Assoc 2002; 288:722e727. 13. Rotter ML. Arguments for alcoholic hand disinfection. J Hosp Infect 2001;48(Suppl. A):S4eS8. 14. EN 1500:1997. Chemical disinfectants and antiseptics. Hygienic hand disinfection. Test method and requirement (phase 2, step 2). Brussels: Comite ´ Europe ´en de Normalisation; 1997.
218 15. EN 12791:2005. Chemical disinfectants and antiseptics. Surgical hand disinfection. Test method and requirement (phase 2, step 2). Brussels: Comite ´ Europe ´en de Normalisation; 2005. 16. Kampf G, Ostermeyer C. Influence of applied volume on efficacy of 3-minute surgical reference disinfection method prEN 12791. Appl Environ Microbiol 2004;70:7066e7069. 17. Kampf G. How effective are hand antiseptics for the postcontamination treatment of hands when used as recommended? Am J Infect Control 2008;36:356e360. 18. Aksoy A, Caglayan F, Cakmak M, et al. An investigation of the factors that affect surgical hand disinfection with polyvidone iodine. J Hosp Infect 2005;61:15e19.
P. Goroncy-Bermes et al. 19. Fuls JL, Rodgers ND, Fischler GE, et al. Alternative hand contamination technique to compare the activities of antimicrobial and nonantimicrobial soaps under different test conditions. Appl Environ Microbiol 2008;74:3739e3744. 20. Gebel J, Werner H-P, Kirsch-Altena A, et al. Hygienische Ha ¨ndedesinfektion e praxisnaher Versuch mit Probanden. In: Standardmethoden der DGHM zur Pru¨fung chemischer Desinfektionsverfahren. Wiesbaden: mhp-Verlag; 2001. p. 29e32. 21. Kampf G, Reichel M, Feil Y, Eggerstedt S, Kaulfers PM. Influence of rub-in technique on required application time and hand coverage in hygienic hand disinfection. BMC Infect Dis 2008;8:149e160.