GROWTH INHIBITION OF CORYNEFORM BACTERIA 213 In a concentration of 0.3%, HGQ completely inhibits the growth of Staphylococcus aureus, Staphylococcus epidermidis, and Propionibacterium acnes (10). The present study was designed to test the bactericidal properties of HGQ against wild strains of corynebacteria isolated from human axillary swabs. Based on biochemical characterization, 30 species of coryneform bacteria were identified from 530 human axillary swabs. These were tested for their sensitivity to HGQ. MATERIALS AND METHODS ISOLATION AND IDENTIFICATION OF CORYNEBACTERIA STRAINS Smears freshly taken with cotton swabs from axillary skin were plated on blood and endoagar. After incubation for 24 and 48 hours at 37øC, potential corynebacteria strains were isolated as individual colonies. They were identified by their typical macromor- phological appearance, being usually gray, opaque colonies, and by gram staining as gram-positive rods. Different strains were identified by examination of the following properties: catalase and oxidase production capacity, [3-hemolysis on sheep blood agar, nitrate reduction, pigment formation, ureases, gelatin hydrolysis, mobility, esculin hydrolysis, serum response, and glucose, lactose, maltose, rhamnose, arabinose, trehalose, saccharose, xylose, and manitol fermentation. Tests were performed and interpreted according to methods described by Coylectal and Lipsky (1), Lenette et al. (13), and Lipstick et al. (16). Reference strains in the tests were a C. diphtheriae Park William-8-strain and a C. pseudotuberculosis strain. The purity of the strains to be iden- tified was checked on blood agar plates before and after application of the inoculum to the test series.* TESTING THE SENSITIVITY OF IDENTIFIED SPECIES OF CORYNEBACTERIA STRAINS TO HGQ The only feasible method proved to be determination of the minimum bactericidal concentration (MBC). 10, 3, 1, 0.5 and 0.25% HGQ stock solutions were prepared in 70% ethanol. Nine milliliters of glucose nutrient broth (Berlin-WeiBensee Institute of Immunopreparations and Nutrient Media) were added to 1 ml of each of the HGQ stock solutions, giving a final HGQ concentration of 1 to 0.025% and an ethanol content of 7%. An inoculating loop was used to inoculate the 6-h preculture, which had been adjusted to 1 million viable microorganisms/mi. An inoculated glucose nutrient broth tube with 7% ethanol served as the positive control, and uninoculated tubes of each of the HGQ concentrations were the negative controls. To ensure a maximum homogeneous distribution of HGQ in the nutrient medium, the tubes were shaken at a moderate rate during the entire 18-h incubation period at 37øC. Aliquots from the shaken culture tubes were spread on blood agar (5% human blood) by means of an inoculating loop. After incubating for 48 h at 37øC, those smears in which less than 0.1% of the original inoculum could be counted as individual colonies were taken as the MBC. * We are grateful to Dr. Med. Lehmann of the Institute of Medical Microbiology and Epidemiology of the University of Leipzig for his assistance with species identification.

214 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS RESULTS The study of 530 axillary swabs and their bacteria isolates reveals a total of 30 coryne- form bacteria (Figure 1). These include C. jeikeium, pathogenic bacteria resistant to antibiotics. All of the C. species listed in Table I are virtually destroyed in the suspen- sion test in the range of 0.025 % to 1% HGQ (99.99% reduction of the initial microbial count). Table I shows that six of the strains studied were already inactivated by a HGQ concentration below 0.025%, another 8 below 0.1%, 9 below 0.3%, and 7 strains below a HGQ concentration of 1%. Although no correlation could be determined between the HGQ sensitivity and specific corynebacteria, there was definitely one between the HGQ sensitivity and the survival time of individual strains. Strains 1-6, which were especially sensitive to HGQ, had the shortest survival times, both on blood agar plates and in the stab culture when stored in the refrigerator. Assessment of the inhibitory (deodorizing) effect of a formulation on skin odor should not be based on the antimicrobial range of the preparation alone. It should also include other specifically use-related tests to enable decisions appropriate to the composition of the preparation. Deodorants are usually assessed by means of the sniff test (8), a sensory method that is based on the evaluation of the underarm odor of a consumer group consisting of at least 30 subjects by a panel of experts with a reliable judgment of odors. The active complex, HGQ, whose effect is to be evaluated in this case, is composed of three natural products that possess some bacteriostatic properties. When the whole group is evaluated after regular use of deodorants and the formulations containing the active ingredient are compared with those containing no active ingredient, the following results are obtained: 100 80 60 40 20 , _•. [23] .................. I41 .................. L[6] ............... 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 HGQ-concentration [%] Figure 1. Minimal bactericidal concentration of HGQ against 30 strains of corynebacteria.