Food Protection Trends - August 2008 - 572

solutions, or 2–4% in detergents. It is active against enveloped viruses, such as HIV, RSV, influenza virus, or cytomegalovirus, but is less effective for the removal of non-enveloped viruses, such as rotavirus, adenovirus, or enterovirus (46, 47). Both antimicrobial compounds need at least two minutes contact time for optimal antimicrobial activity. Hence, it is very important that the antibacterial soap is not washed away immediately. Furthermore, the antimicrobial activity of these antimicrobial components is considerably reduced in the presence of organic dirt on the skin surface, or by some hand creams containing anionic emulsifiers. It has also been shown that anionic detergents in lotions that are used to maintain optimal skin health can neutralize the activity of CHG. Therefore, the antibacterial soap has to be chosen with care (36). Hand drying. Drying hands, in addition to handwashing, considerably reduces the risks associated with contaminated hands. Residual moisture layers present on the skin of hands can act as an interface facilitating the transfer of microorganisms from hands to other surfaces. Moreover, a correlation was demonstrated between the time-span taken for hand drying and the reduction in number of transferred microorganisms. This correlation was observed when either an air dryer or towels were used. Furthermore, a synergetic effect was observed when the air dryer was combined with the use of towels, which resulted in a 99% reduction of the transfer of microorganisms compared to non-dried hands (89, 114). Hands can be dried in four different ways: using a hot air dryer, using cloth towels, using paper towels, or by evaporation. Each technique has its own advantages and disadvantages. Drying by evaporation is obviously time-consuming and is therefore not recommended. Cloth towels not changed after use are a major source of contamination. Residual moisture on the cloth contributes to a suitable niche for the microorganisms to grow in. Repeated use of cloth for drying hands therefore results in extreme accumulation of microorganisms. As a consequence, the use of cloth towels can be recommended only when they are changed after every use. The quality of the paper towels is also found to contribute to the efficacy of microorganism removal; bad paper quality can cause skin damage due to friction or to insufficient drying. Soft and well absorbent paper towels give the best results. The major disadvantage of hot air dryers is that it takes considerable time to dry hands effectively (41). The available experimental data are not unequivocal regarding the most effective hand drying method. Some authors state that, in comparison with hot air dryers, the use of paper towels results in a greater reduction of microorganisms. The higher efficacy is attributed to the fact that the use of towels also results in the physical removal of microorganisms (13, 98). Moreover, it has been stated that the use of air dryers may result in increased microorganisms on the skin surface because air dryers may blow microorganisms that are present in the washing facility or in the air dryer itself, directly onto the skin. This belief was mentioned in a 1994 University of Westminster study (98) and this study’s findings were later cited in other reports, thereby spreading this belief (85). Nonetheless, these data were refuted in another study that did not find a statistically significant difference in the efficacy of four different hand drying methods. On the contrary, air dryers were found to be slightly more effective in the reduction of bacteria than other hand drying techniques, although, this difference was not considered significant (41, 114). What can be deduced from these conflicting data? There is probably no significant difference in the efficacy of the different hand drying techniques, provided that the hands are dried thoroughly. Hence, the important parameter in the reduction of microorganisms is not the applied drying technique itself but rather the extent to which the hands are dried. Pros and cons of soap. The main advantage of washing hands with soap is the simplicity of the procedure. When the described procedure is carried out properly, washing the hands is a highly effective method of reducing the spread of pathogens by contaminated hands. Washing hands thoroughly results in a 2–3 log reduction in the transfer of microorganisms from hands to food. However, handwashing techniques also have their disadvantages. Washing hands with soap causes skin damage, particularly when hands are washed frequently over a long period of time. During each handwashing procedure, the water-lipid layer of the skin surface is altered, and protecting components that are essential for maintaining an optimal skin barrier, such as glycerolipids, sterols, or amino acids, are washed away. In addition, natural antimicrobial components, such as some fatty acids with fungicidal and bactericidal activity, that are present in the upper layer of the skin are important in modulating the skin microflora and are also removed by washing procedures (47, 56, 57). A correlation was observed between the frequency of handwashing and skin damage (57). The skin recovers only to some degree after washing. After three hours, approximately 50% of the barrier function is restored (55). Skin damage is detrimental to good hand hygiene for several reasons: a decrease in skin health results in an increase of microorganisms present on skin; damaged skin also harbors more pathogenic microorganisms than healthy skin; washing damaged skin is far less effective in the removal of microorganisms compared to washing healthy skin; and skin damage can often cause eczema or dermatitis (56). This stresses the importance of healthy skin in the war against the spread of pathogenic microorganisms. Therefore, emollients or other skin-softening additives that reduce skin damage are often added to liquid soaps. A second disadvantage of washing hands is the risk of contamination during washing. For instance, the sink can be a major source of contamination because the moisture in the sink provides a good habitat for microorganisms. In addition, after long periods of time, the soap dispenser, and the soap itself —particularly solid soap—can become contaminated with microorganisms (108). These surfaces can contribute considerably to cross contamination through contact with dirty or contaminated hands that have not yet been washed. Likewise, conventional water taps can be a source of contamination or recontamination, which can be circumvented by using tissues when turning on or off the tap or by using foot or elbow operated taps. Even better is the use of sensor driven hand-free water taps and dispensers (85). Montville et al. (85) developed a mathematical model based on the avail- 572 FOOD PROTECTION TRENDS | AUGUST 2008

Food Protection Trends - August 2008

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