Bacteriological Studies Relating to Handwashing

Washing with contaminated bar soap is unlikely to transfer bacteria

“…aeruginosa was also recovered from one of these two bars. (Bannan & Judge, 1965). Unlike the original method, we employed a direct and more controlled inoculation procedure.…”

“…Because we wanted to use a direct inoculation procedure rather than relying on panelists washing with contaminated hands to inoculate the soap (Bannan & Judge, 1965), it was necessary to precondition the soap bars (Kabara & Brady, 1984). We chose to prewash and water soften previously used tests bars immediately prior to inoculation and panelists usage.…”

“…Rather than inoculation with S. marcescens as previously done (Bannan & Judge, 1965), we chose to use two other Gram-negative bacteria, Escherichia coli and Pseudomonas aeruginosa. Gram negatives were used since the antimicrobial agent in the test soap, triclocarban, is not active against these bacteria (MIC greater than 1000 p.p.m., unpublished data) and because we found in preliminary experiments that they survive better on soap bars than do Gram-positive bacteria, confirming published results with inoculated bars (Kabara & Brady, 1984).…”

“…It is not surprising that microorganisms, which are ubiquitous in the environment, have been isolated from in-use soap bars (Bannan & Judge, 1965;Litsky & Litsky, 1967;Kabara & Brady, 1984;McBride, 1984). Such results, however, raise the question of whether or not bacteria can be transferred to hands from used soap bars during handwashing.…”

“…Such results, however, raise the question of whether or not bacteria can be transferred to hands from used soap bars during handwashing. The only study directly addressing this question was published over 20 years ago (Bannan & Judge, 1965). In this study 10 panelists, whose hands were inoculated with 5 x 109 c.f.u.…”