Food Protection Trends - August 2008 - 573

able experimental data and concluded that the combined use of CHG soap, paper towels, and disinfectants in combination with a hand-free water tap, along with a prohibition on wearing rings, resulted in a reduction of the total bacterial count on skin of the hand of 3 log CFU or more in 90% of the cases. However, the total microbial count after use of other soaps or sanitizers is also in this range, provided that the described procedures are properly executed. Recommended hand washing. Handwashing should be carried out exactly according to approved procedures. The following is an example of such a procedure: Wet hands under running water; Take a 20 mm blob of soap; Rub hands vigorously together for at least 15 seconds, taking care not to overlook wrists, palms, thumbs and fingernails; Rinse hands thoroughly with running water; Dry hands thoroughly, preferably with single-use towels (paper or cloth); and Turn off the water tap, using the elbow or a tissue to prevent recontamination. Some authors recommend the use of warm water to increase the efficacy of hand washing. However, the effect of using warm water has been investigated thoroughly and it has been shown that water temperature had no significant effect on the efficacy of microorganism reduction (80). On the contrary, the use of hot water increases skin damage, which is detrimental to good hand hygiene. Thorough washing of the hands with soap takes a long time in comparison with hand disinfection. In practice, the time needed for rubbing the hands with soap (at least 15 s) is seldom fulfilled, which results in a severe decrease of efficacy. Finally, special attention also has to be given to thumbs, because these typically contain the most dirt and are usually not washed properly. Several studies demonstrated that thumbs are often a contamination source, even when hands are washed frequently (72, 81). Disinfection of hands with alcohol-based sanitizers Alcohol-based sanitizers: quick and effective. Sanitizers of these are used for hand disinfection and are usually based on ethanol, isopropanol, n-propanol, or a combination of these. n-Propanol is regarded as the most effective alcohol in the removal of microorganisms, followed by isopropanol and ethanol. Alcohols are characterized by a very fast mode of action and by their antimicrobial activity against a wide range of microorganisms. They are active against Gram-negative and Gram-positive bacteria, against mycobacteria, against fungi, and against enveloped viruses. However, alcoholbased sanitizers have little effectiveness against bacterial spores, oocytes, and non-enveloped viruses (46, 47). The action of alcohol-based sanitizers is based on denaturation of proteins and lysis of the cell membrane. Although hand alcohols are proven to have disinfecting properties, the removal of microorganisms from skin by use of alcoholbased sanitizers is largely attributed to physical removal when the hands are rubbed together, as also occurs with use of soap. Antimicrobial compounds, such as hexachlorophene, triclosan, quaternary ammonia or chlorhexidine gluconate, are therefore often added to alcohol-based disinfectants. In comparison to antibacterial soaps, the additives remain on the hands for a longer period of time, because they are not washed away during rinsing, and they can therefore exert their effect for a longer period of time. In addition, these additives often prolong the antimicrobial effect by slowing down the evaporation of alcohol (46). The use of the correct concentration is very important. For instance, sanitizers with 60% ethanol concentrations have greatly decreased antimicrobial activity, while those with ethanol concentrations above 95% lose antibacterial activity because such sanitizers contain too little water to denature proteins (53). Hence, an optimal alcohol concentration has to be chosen to give the best results over a wide range of microorganisms. The optimal ethanol concentration to kill and remove bacteria from the skin is 70%, while viruses are best removed by use of 95% ethanol. Pros and cons of hand alcohol. One of the benefits of alcohol-based disinfection is that the described procedure is simple, takes very little time, and does not need sinks, water taps, or drying equipment such as towels or air dryers. Another advantage of alcohols is their activity against a wide range of microorganisms and their fast mode of action. A major disadvantage of alcoholbased disinfection is the inability to remove organic material or dirt from the skin surface. Consequently, alcohols are not able to reach the microorganisms that are embedded in the organic matrix so as to exert their antimicrobial activity. Secondly, the frequent use of alcoholbased sanitizers can cause skin irritation, although to a lesser extent than to the use of soap. Alcohols not only dehydrate the skin but also remove skin oils. The total alcohol concentration mainly determines the extent of skin damage. However, ethanol is regarded as more harmful to the skin than, for instance, isopropanol. Combinations of different alcohols (e.g., ethanol and isopropanol) maintain their effectiveness, but with a reduced total alcohol concentration. This is very useful, because lower total alcohol concentrations are less damaging to the skin. Glycerin is often added at a concentration of 1–4% to reduce skin irritation caused by the use of alcohol-based sanitizers. The addition of skin softeners or emollients to the alcohol rubs slows down skin damage and also ameliorates the antimicrobial effects of the alcohol, probably because the alcohol evaporates more slowly when softeners or emollients are added, so that the alcohols are active for a longer period of time (56). Alcohol gels are also better for skin health and reduce skin damage, dehydration and irritation. Such disinfecting gels have been shown to be useful in reduction of infections in a clinical environment, but their value in the food industry remains to be investigated. Kramer et al. (53) examined the efficacy of several alcohol-based hand gels and concluded that these gels are less effective than liquid alcohol rubs in reducing microorganisms. However, recent developments have improved the efficacy of alcohol gels. With addition of suitable polymers, the gel liquefies faster, enabling better coverage. In addition, the amount of alcohol gel applied is crucial to its efficacy. It was demonstrated that doubling the volume of applied gel significantly improves efficiency of coverage of the hands with the gel, which may result in lower bacterial counts on the hands (72). Considering that alcohol gels are beneficial to the skin and that good skin health is highly important to maintenance of good hand hygiene, alcohol gels may even be the preferred choice for long-term use. AUGUST 2008 | FOOD PROTECTION TRENDS 573

Food Protection Trends - August 2008

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