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Washing with contaminated bar soap is unlikely to transfer bacteria

  • John E. Heinze (a1) and Frank Yackovich (a1)

Recent reports of the isolation of microorganisms from used soap bars have raised the concern that bacteria may be transferred from contaminated soap bars during handwashing. Since only one study addressing this question has been published, we developed an additional procedure to test this concern. In our new method prewashed and softened commercial deodorant soap bars (0·8% triclocarban) not active against Gram-negative bacteria were inoculated with Escherichia coli and Pseudomonas aeruginosa to give mean total survival levels of 4·4 × 105 c.f.u. per bar which was 70-fold higher than those reported on used soap bars. Sixteen panelists were instructed to wash with the inoculated bars using their normal handwashing procedure. After washing, none of the 16 panelists had detectable levels of either test bacterium on their hands. Thus, the results obtained using our new method were in complete agreement with those obtained with the previously published method even though the two methods differ in a number of procedural aspects. These findings, along with other published reports, show that little hazard exists in routine handwashing with previously used soap bars and support the frequent use of soap and water for handwashing to prevent the spread of disease.

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E. A. Bannan & L. F. Judge (1965). Bacteriological studies relating to handwashing. American Journal of Public Health 55, 915922.

J. E. Heinze (1985). Bar soap and liquid soap. Journal American Medical Association 253, 1561.

J. D. Jarvis , C. D. Wynne , L. Enwright & J. D. Williams (1979). Handwashing and antiseptic-containing soaps in hospital. Journal of Clinical Pathology 32, 732737.

J. J. Kabara (1985). Bar soap and liquid soap. Journal American Medical Association 253, 15601561.

A. C. Steere & G. F. Mallison (1975). Handwashing practices for the prevention of nosocomial infections. Annals of Internal Medicine 83, 683690.

P. Williamson & A. M. Kligman (1965). A new method for the quantitative investigation of cutaneous bacteria. Journal of Investigative Dermatology 45, 498503.

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Epidemiology & Infection
  • ISSN: 0950-2688
  • EISSN: 1469-4409
  • URL: /core/journals/epidemiology-and-infection
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