40 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS examined by a cup plate method on malt extract agar, to which sterile cream had been added. The plates were flooded with sterile cream diluted 1 in 20 with normal saline, re-dried and then inoculated with a 3 day old culture of the fungus. After 3 and 7 days incubation at 37 ø C it was found that Dequalinium chloride had not inhibited the growth of the fungus at concen- trations extending to 400 /•g/ml. This absence of activity was thought to be due to the inactivation of Dequalinium by the agar culture media. Further experiments were performed by tube dilution methods in a modifica- tion of Curries medium TM and also in two other broth culture media. The results of these experiments are summarized in Table 1, which shows the composition of each culture medium, the concentration of added lipoid and the minimum inhibitory concentration (M.I.C.) of Dequalinium chloride in /•g/ml. It is apparent from these results that the fungistatic activity of Dequalin- ium cannot be evaluated in a medium containing agar. From the experi- ments using liquid media it is clear that a lipoidal substance must be added to the culture fluid to permit the normal growth of the fungus the addition of 0.05 per cent sterile cream or 0.5 per cent oleic acid would appear to satisfy the nutrient requirements of the fungus however, oleic acid markedly inhibits the activity of Dequalinium chloride. A malt-extract broth containing 0.05 per cent sterile cream in emulsified form was used in later experiments. This medium was selected from those liquid media found to be suitable because it consistently supported a luxurious growth of the fungus and did not noticeably reduce the fungistatic properties of Dequalinium. Dequalinium chloride and Dequalinium stearate were then examined for their activity against P. ovale. These results are summarized in Table 2, which lists the M.I.C. value for the salts in/•g/ml. TABLE 2 The inhibitory activity of some Dequalinium salts against Pityrosporum ovale. Culture Added Fat Geometric mean M.I.C. Compound Medium Source in/•g/ml at 7 days Dequalinium Malt-extract Sterile cream 5.1 chloride broth 0-05 per cent Dequalinium Malt-extract Sterile cream 8.8 stearate broth 0.05 per cent Both the salts were found to show marked fungistatic activity against the organism. Infectious dandruff of the scalp is in many cases further complicated by

DEQUALINIU1V[ SALTS AND PITYROSPORUM OVALE 41 the presence of other bacteria and fungi in the hair and skin. Dequalirdum was therefore examined for its anti-microbial activity against some of these organisms the results are shown in Table 3, which lists the M.I.C. value for Dequalinium in/•g/ml. TABLE 3 The inhibitory activity of Dequalinium against certain micro- organisms of hair and skin. Micro-organism Staphylococcus aureus Staphylococcus saprophyticus Sarcina luteat Streptococcus pyogenes Escherichia coli Bacillus subtilis Proteus vulgaris Candida albicans Microsporum canis Trichophyton mentagrophytes Trichophyton rubrum Trichophyton verrucosum Geometric mean M.I.C. in/•g/ml at ' 5 days 0.20 0.28 0.17 1-10 9'50 2.50 100 0.63 -- 14 days 0-60 O.O8 0.59 1.67 Since Dequalinium exerts its anti-microbial action not by killing the micro-organism but by preventing its growth, it is obvious that the time of contact between drug and hair is of importance, therefore the degree of adsorption of the compound b,y hair was studied. Samples of human hair were allowed to soak for varying times in graded concentration of Dequalin- ium the hair samples were then washed in distilled water and allowed to dry for 30 min in warm air. The amount of the compound adsorbed on to the hair was then evaluated by determining the bacteriostatic activity of the hair sample against S. aureus, after 24 hours' incubation at 37 ø C. These results are shown in Table 4. TABLE 4 The adsorption of Dequalinium by samples of human hair. Results expressed as/•g. Dequalinium per mg. of hair. Dequalinium concentration per cent 4.0 2.0 1.0 10 2-5 1.25 0.62 Contact time min. 30 2.5 1-25 0.62 60 2.5 1.25 1.25