Outbreaks Where Food Workers Have Been Implicated in the Spread of Foodborne Disease. Part 10. Alcohol-Based Antiseptics for Hand Disinfection and a Comparison of Their Effectiveness with Soaps

ABSTRACT

Alcohol compounds are increasingly used as a substitute for hand washing in health care environments and some public places because these compounds are easy to use and do not require water or hand drying materials. However, the effectiveness of these compounds depends on how much soil (bioburden) is present on the hands. Workers in health care environments and other public places must wash their hands before using antiseptics and/or wearing gloves. However, alcohol-based antiseptics, also called rubs and sanitizers, can be very effective for rapidly destroying some pathogens by the action of the aqueous alcohol solution without the need for water or drying with towels. Alcohol-based compounds seem to be the most effective treatment against gram-negative bacteria on lightly soiled hands, but antimicrobial soaps are as good or better when hands are more heavily contaminated. Instant sanitizers have no residual effect, unlike some antimicrobial soaps that retain antimicrobial activity after the hygienic action has been completed, e.g., after hand washing. Many alcohol-based hand rubs have antimicrobial agents added to them, but each formulation must be evaluated against the target pathogens in the environment of concern before being considered for use. Wipes also are widely used for quick cleanups of hands, other body parts, and surfaces. These wipes often contain alcohol and/or antimicrobial compounds and are used for personal hygiene where water is limited. However, antiseptics and wipes are not panaceas for every situation and are less effective in the presence of more than a light soil load and against most enteric viruses.

This is the 10th article in a series on food workers and foodborne illness. In the first three articles, the authors described the types of outbreaks identified during a review of 816 published and unpublished reports and how workers contributed to these outbreaks (49, 130, 131), and the next three articles provided information on infective doses, pathogen carriage, sources of contamination, pathogen excretion by infected persons, and transmission and survival of pathogens in food environments (132-134). In the seventh and eighth papers, the authors discussed physical barriers to contamination and the pros and cons of glove use (136, 137). In the ninth article, hand hygiene for removing as much soil (bioburden) from fingers and other parts of hands as possible, the effectiveness of various soaps (with and without antimicrobial compounds), and the need for drying hands to remove loose microorganisms from the skin surface were discussed (138). The present article provides a discussion of the increasing use of antiseptics and sanitary wipes in the health care and food industries and the effectiveness of various soaps and antiseptics or sanitizers under different conditions.

DEFINITIONS

Weber et al. (147) defined germicides as biocidal agents, such as antiseptics, disinfectants, and preservatives, that inactivate microorganisms. Antiseptics are antimicrobial substances that are applied to the skin or mucous membranes to reduce the microbial flora. Disinfectants are substances that are applied to inanimate objects to destroy harmful microorganisms, although disinfectants may not kill bacterial spores. Preservatives (antimicrobials) are incorporated into soaps and other antiseptics to prevent microbial growth.

Hand disinfection can be defined as the application of a chemical agent with antimicrobial activity to the hands. Reduction of the resident flora depends on the ability of the topical antimicrobial product to produce an immediate and persistent residual effect (104). The terms "hand antiseptic" or "alcohol-based hand rub" (ABHR) are more often used than "hand sanitizer," especially in Europe (121, 145). In the 2005 version of the U.S. Food and Drug Administration (FDA) Food Code (144), the term "hand sanitizer" was changed to "hand antiseptic" to eliminate confusion with the term "sanitizer" (a defined term in the Food Code) and to more closely reflect the terminology used in the FDA monograph for health care concerning antiseptic drug products for over-the-counter human use (143).

The term "sanitizer" is typically used to describe a substance used to control bacterial contamination of inert objects or articles, equipment and utensils, and other food contact surfaces, usually a strong chemical solution such as sodium hypochlorite or a quaternary ammonium compound. The Food Code definition of "sanitizer" requires a minimum microbial reduction of 5 log units, which is equal to a 99.999% reduction. Most antimicrobial hand agents typically achieve a much smaller reduction and so are not consistent with the definition of "sanitizer" in the Food Code.

A hand antiseptic solution used as a hand dip should be kept clean and at a strength equivalent to at least 100 mg/ liter chlorine. An antimicrobial soap with an E2 designation requires activity equivalent to 50 ppm of chlorine. However, because "sanitizer" and "antiseptic" are used interchangeably in the literature with possibly different meanings it is not always easy to separate the two, and both are used in this article.

Four types of hand disinfection were described by Smith (121) based on hospital requirements. Hygienic hand disinfectants are alcohol-based agents used to rapidly kill transient organisms on the hands (i.e., within 15 to 30 s) but may have an additional antimicrobial effect on resident microflora. Hygienic hand disinfectants with residual activity differ from alcohol-based agents because repeated use of hexachlorophene, iodophors, alcoholic chlorhexidine, and chlorhexidine leads to longer residual activity. These agents can destroy both the existing transient bacteria and other bacteria (e.g., Staphylococcus aureus) that may subsequently contaminate the hands. Surgical hand disinfectants are agents that remain active against both transient and resident organisms for 2 to 4 h (e.g., povidone-iodine and chlorhexidine) and are less commonly used in food facilities.

Basic hand disinfection includes use of the agents described below, which are designed to continually reduce the density of resident organisms and are particularly useful for food, pharmaceutical, and health care workers. The effectiveness of these agents is based on application frequency, with repeated use giving a greater reduction in hand flora than that obtained with a single treatment. Hand disinfection agents approved for use in the food industry are limited because compounds that are potentially toxic to consumers or affect the taste or appearance of the food are not permitted. However, these agents must have sufficient activity against a wide range of microorganisms. Most of the compounds that meet these criteria are liquid soaps. Powdered soaps containing borax (sodium borate decahydrate) are available for heavy duty hand cleaning, to use as laundry detergents, or to remove grease under cold washing conditions and may be effective in hard water but are rarely used in the food industry for hand washing. Some of the agents most frequently used are listed below and mentioned briefly elsewhere in this article, especially when they are used in combination with alcohol. Alcohol-based compounds used as antiseptics are discussed in more detail in the following sections.

Chlorhexidine. This hand disinfectant is effective against gram-positive cocci and to a lesser extent gramnegative bacteria and fungi at 4% concentrations or at 0.5 to 2% (wt/vol) alcohol, e.g., 0.5% in 70% isopropanol. Chlorhexidine gluconate (CHG) is commonly used in health care facilities.

Quaternary ammonium compounds ("quats"). These products, typically used for cleaning equipment in food operations, are bacteriostatic and fungistatic. Benzalkonium chloride (BAC) is the quaternary ammonium compound most often used in health care settings.

Iodophors. These compounds (e.g., 7.5 to 10% povidone) are effective against both gram-positive and gram-negative bacteria and some spore-forming bacteria.

Triclosan. Triclosan is widely used at concentrations of 0.2 to 2% and exhibits bacteriostatic activity against grampositive bacteria and to a lesser extent on other bacteria and fungi.

Ozone. The use of 4 ppm of ozonated water in combination with 0.2% BAC and 83% ethanol is an effective method of hand disinfection. However, Michaels and coworkers (85, 86) found that there was no significant difference between hands washed with water containing 3 ppm of ozone combined with bland soap (without antimicrobial compounds) or soap containing 0.2% BAC and hands washed with nonozonated water. Therefore, the combination of ozone and alcohol appears to be more important for disinfection than combination of soap with ozonated water.

ALCOHOL INSTANT HAND ANTISEPTICS, SANITIZERS, AND RUBS

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