[Value of a standard exudate in the in vitro study of antiseptics]

Bactericidal activity of antiseptics is generally determined in France according the AFNOR norms the principles of which have recently been reconsidered by the Pharmacopoeias. These norms preconize the use of either hard water (12 Ca++ milliequivalents) or a mixture of proteins (albumin-yeast extract) to appreciate any loss of activity by interference. However these two interfering substances are very different from exudates on wounds or burns. This is why we have prepared a standard exudate composed of dried bovine albumin (Cohn fraction V for bacteriology) 4% m/V; Ca++ 0.01% m/V and Mg++ 0.003% m/V. These protein and ion concentrations correspond to the percentage of these elements in plasma. A first sequence of assays on two antiseptics, one with a chlorhexidine base, the second with a iodine polyvidon base allowed us to study individually the interference of proteins, of ions, and that of the standard exudate. The first results showed that for the iodine polyvidon the effect of ions was slight compared with the effect of proteins whereas for chlorhexidine the effect of ions was a strong as that of proteins. Therefore we have used this standard exudate in the study of other antiseptics according to the protocol of the norms NF T 72-170. Results showed that the standard exudate strongly inhibits the bactericidal activity of antiseptics. We propose that its use be generalised in the in vitro study of antiseptics destined for cutaneous or mucous lesions.