[Microbiological characteristics of selected liquid soaps for hands washing].

Introduction: According to common belief, supported by the authority of the World Health Organization - WHO, the common (social) hand washing is the simplest, cheapest and the most effective way of reduction the hospital-acquired infections. For this purpose products of"liquid soaps", present in a large number on the market, are most often applied. Microbiological status (microbiological purity and antimicrobial activity) of"liquid soaps" available on the Polish market is not known, because relevant routinely studies have not been performed. Only the antibacterial and / or antifungal activity of certain formulations is sometimes assessed, especially when the manufacturer suggests the standardized application of the products for surgical or hygienic procedures. The aim of this study was to determine the microbiological quality, especially microbiological purity and antimicrobial activity of the selected hands washing products, presents on the Polish market.

Methods: The 12 selected commercial products, available on the market in Poland, dedicated for hands washing were included into study. Microbiological purity test was carried out in accordance with the Polish Pharmacopoeia (FP) monograph (FP monograph numbers correspond to numbers of the European Pharmacopoeia monograph- Ph. Eur.) No 2.6.12 "Microbiological examination of non-sterile products: microbial enumaration tests", and the monograph of FP No. 2.6.13 "Microbiological examination of non-sterile products: test for specified microorganisms". The following physico-chemical properties of soaps were examined: the pH of the formulations was measured according to the monograph FP No. 2.2.3. "Potentiometric determination of pH", the density of products was assayed according to the monograph FPNo. 2.2.5. "Relative density" and determination the water activity was performed by monograph FP No 2.9.39 "Water-solid interactions: determination of sorption-desorption isotherms and of water activity". Next, antibacterial and antifungal protection was determined in accordance with the monograph FP No 5.1.3. "Efficacy of antimicrobial preservation". The study of antimicrobial activity was carried out in accordance with PN-EN 1040 "Chemical disinfectants and antiseptics - Quantitative suspension test for the evaluation of basic bactericidal activity of chemical disinfectants and antiseptics - Test method and requirements (phase 1)". Finally, using the "time-kill" method the survival of microorganisms after different contact times of the products with bacteria and fungi were determined.

Results: All the examined products showed a very high microbiological purity. None of the formulations was characterized by a high acidity or alkalinity. All the analyzed products were slightly thicker than water, but such density of the preparation does not seem to be important parameter in the growth of microorganisms. The results of water activity estimation - the parameter indicating the presence of free, not chemically bound water stimulating microbes growth - do not show that low water content in the preparation may inhibit bacteria and fungi growth. Taking into consideration the antimicrobial protection of the products demonstrated in the tests carried out in accordance within FP monograph No 5.1.3. and PN-EN 1040, and analysing curves indicating killing rate of bacteria and fungi obtained by "time-kill" method, the microorganisms contaminating the products generally should not multiply in their environment, and gradually they die - what can take many hours or even days.

Conclusions: The cases of bacterial infections connected with the usage of non-medical liguid soaps, applied in the health care units and described in the literature, should be considered as related rather to contamination of plastic packaging and dosage system, then to contamination of preparation itself inside the package. It was proved, that in all tested products amount of contaminating microbes diminishes in time. The dynamics of this process depends on the microorganisms character - bacteria dies quicker then fungi. The special attention should be given to washing, cleaning and disinfection of preparation dispensing systems, to avoid microbial contamination of product doses applied directly on the hands. It should be emphasized that only formulations containing antimicrobial agents in an appropriate amount, eliminate microorganisms from the skin surface fast and effectively. In case of hygienic and surgical procedures following the standardized manner in order to obtain required reduction rate of microorganisms in a short time - only products complying with appropriate EN standards are suitable. For these puroposes, the popular "liquid soaps" should not be used.