Antimicrobial efficacy of biocides tested on skin using an ex-vivo test

An ex-vivo test was used to evaluate the activity of antimicrobials against three microorganisms, Escherichia cell, Pseudomonas aeruginosa and Staphyl ococcus aureus. The ex-vivo test is a carrier test using freshly excised an imal skin samples maintained in viable conditions far a short period of tim e. Skin samples came from a veterinary practice and were excised from eithe r dogs or cats. The antimicrobial activity of povidone iodine, chlorhexidin e diacetate, cetrimide and benzalkonium chloride was also evaluated with su spension and glass-carrier tests. Generally, the activity of the antimicrob ials tested was reduced when applied to the skin surface. Apart from povido ne iodine (2%) against S. aureus, the biocides investigated failed to achie ve a 5 log(10) reduction in bacterial titre when tested with the ex-vivo me thod. There was no significant difference in reduction of bacterial titres after treatment with antimicrobials between the glass-carrier and the suspe nsion tests. Furthermore, the drying process of bacterial inoculum was less detrimental on skin than on glass surfaces. This study confirmed that the activity of a biocide tested in suspension or on an inanimate surface did n ot reflect its activity when tested on skin. Further development of the ex- vivo test may be useful, especially for testing the antimicrobial activity of formulations with antiseptic properties.