The efficacy of hygienic hand wash procedures for food handlers using germicidal soaps and hand dips was studied by measuring changes in numbers of microorganisms released from hands before and after each of two successive 15-s treatments. Both hand rinse and finger tip imprint sampling techniques were used. The experiment consisted of two (6 × 6) Latin square designs, each including a non-germicidal soap control. Of the hand dip agents, including sodium hypochlorite (50 ppm available chlorine), iodophor (25 ppm available iodine) and a quaternary ammonium compound (QAC) (930 ppm benzalkonium chloride), only the QAC gave a statistically significant decrease in the number of bacteria released when tested by the finger imprint technique. This experiment included a bar soap containing 1.0% trichlorocarbanilide which gave results equivalent to the non-germicidal soap control. Of the hand wash agents, 4% chlorhexidine gluconate and iodophor (0.75% available iodine) resulted in significant decreases in numbers of bacteria released when tested by either sampling technique. Products containing Irgasan DP 300 (0.25% active ingredient at the use concentration), tribromosalicylanilide (0.5%) and para-chloro-meta-xylenol (0.325%) were no better than the non-germicidal soap control under the conditions of this experiment. Identification of 3,591 aerobic isolates from finger imprint plates indicated that Staphylococcus epidermidis and Micrococcus spp. were the predominating organisms (85.3%) released from the hands.
1Supported by funds from Agriculture Canada, Research Contract.
2Department of Food Science.
3Department of Foods and Nutrition and Department of Microbiology.