An extended model for transfer of micro-organisms via the hands: differences between organisms and the effect of alcohol disinfection

Abstract

SUMMARYA model for contact transfer of micro-organisms by hand has been extended to include representatives of bacterial species responsible for a majority of hospitalacquired infections. The ability of the organisms to transfer from contaminated fabrics to hands and from hands to sterile fabrics was measured, as was their ability to survive on the skin of the hands. There were differences between the species. Staphylococcus saprophyticus transferred well to the hand but not as well from hand to fabric as the other species; it survived well on skin. Pseudomonas aeruginosa, Klebsiella aerogenes and Serratia marcescens transferred moderately well overall and also survived on the skin. These results were in contrast to those obtained with a strain of Escherichia coli and one of Streptococcus pyogenes.The contact transfer model was used to investigate the use of small volumes of alcohol in preventing transfer via the hands. An alcohol handrub of either 0-3 ml 80 % ethanol or 0 3 ml 70 % isopropanol gave reductions in transfer slightly less than that of a soap and water wash. Raising the volume, and consequently the contact time, to 0 5 ml 70 % isopropanol gave a 14000-fold reduction in transfer, statistically indistinguishable from that of a thorough soap and water wash (9800-fold reduction).

Using Alcohol for Hand Antisepsis: Dispelling Old Myths

“…Mackintosh found that application of 0.3 mL to the hands was no more effective than plain soap-and-water hand washing. 45 Simply increasing the volume to 0.5 mL increased the effectiveness of alcohols substantially. Larson demonstrated that 1 mL of alcohol was significantly less effective than applying 3 mL to the hands.…”

Evaluation of Microbial Contamination in Frequently Used Fomites in Kuwait

“…These include bacteria type, source and destination surfaces, time post inoculation, and moisture level. 10,11 Montville et al 12 investigated bacterial transfer rates from food to hands and from hands to food with and without a glove barrier. 12 The authors found that a glove barrier can decelerate the transfer rate of microorganisms from food to hands.…”

Hand Hygiene

“…Overall, only 0.06% of the organisms obtained from the contaminated donor fabric were transferred to the recipient fabric via hand contact. Using the same experimental model, Mackintosh and colleagues 169 found that S. saprophyticus, P. aeruginosa, and Serratia spp. were transferred in greater numbers than was E. coli from a contaminated to a clean fabric following hand contact.…”

“…179 A few studies have examined the ability of alcohols to prevent the transfer of health care-associated pathogens by using experimental models of pathogen transmission. 74,88,169 Ehrenkranz and colleagues 88 found that Gram-negative bacilli were transferred from a colonized patient's skin to a piece of catheter material via the hands of nurses in only 17% of experiments following antiseptic handrub with an alcohol-based hand rinse. In contrast, transfer of the organisms occurred in 92% of experiments following handwashing with plain soap and water.…”

“…Small volumes (0.2-0.5 ml) of alcohol applied to the hands are no more effective than washing hands with plain soap and water. 74,169 Larson and colleagues 151 documented that 1 ml of alcohol was significantly less effective than 3 ml. The ideal volume of product to apply to the hands is not known and may vary for different formulations.…”