J. Soc. Cosmet. Chem., 38, 223-231 (July/August 1987) Efficacy of the antimicrobial agent triclosan in topical deodorant products: Recent developments in vivo ASHLEY R. COX, Microbiology Department, FC 2.46, Ciba-Geigy AG, Dyestufj5 & Chemicals Division, CH-4002 Bask, Switzerland. Received February 10, 1987. Synopsis In vivo studies have been conducted to determine the effects of application of deodorant and antiperspirant products on aerobic axillary microbial populations and to quantify the influence of the antimicrobial agent triclosan on product efficacy. Antibacterial effects of alcohol and antiperspirant ingredients were augmented by inclusion of triclosan in deodorant compositions and, in the case of a deospray composition containing 0.15% triclosan, improve- ment in deodorancy was established by olfactory studies. The axillary microflora, predominently Gram-positive micrococci and coryneform bacteria, showed a sus- tained reduction during six months' usage of triclosan-containing deodorants, and Gram-negative bacteria, carried in low numbers by 50% of test subjects, were, in general, quickly eliminated. Resistant popula- tions, though, were not established, and no replacement or "overgrowth" with opportunist transients was evident. On discontinuation of deodorant application, bacterial numbers in the axillae returned to pre- usage levels within four to seven days. INTRODUCTION Although a variety of materials have been suggested to reduce perception of body and underarm malodor (1), the majority of deodorants (aerosols, pumps, sticks, roll-ons, creams, and soaps) currently marketed incorporate an antimicrobial agent as active in- gredient. Such compounds are included to inhibit growth of the microbial populations responsible for sweat degradation and malodor generation. The compound most widely used in this context has been triclosan. Marketed since 1967, • triclosan (2,4,4'-tri- chloro-2'-hydroxydiphenyl ether) exhibits broad-spectrum antimicrobial activity, in- cluding efficacy against bacteria of hygiene and clinical importance (2,3). Two main approaches are used to study in vivo efficacy of topical deodorants: determina- tion of effects on skin microbial populations and olfactory evaluation of skin odors. Both approaches have proved useful in our experience for determination of triclosan efficacy following both short-term (3 days) and long-term (6 months) application of aerosol deodorants. In addition, studies have been conducted to examine the influence of tri- closan inclusion on sustained antibacterial efficacy of antiperspirant roll-ons and sticks. • Irgasan © DP 300, Ciba-Geigy. 223

224 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS MATERIALS AND METHODS DETERMINATION OF EFFECT ON SKIN MICROFLORA Aerobic bacteria were quantitatively recovered from the middle axillae region of sub- jects, utilizing the "Thran" pressurized spray gun as previously described by ourselves (4) and other workers (5) and enumerated, via serial dilution or where appropriate, by membrane filtration of sampling fluid, in suitable agar recovery medium, following 2-4 days incubation at 37øC. The axillary microflora were differentiated, where indi- cated, by use of selective growth media in conjunction with Gram-staining and diag- nostic testing of isolated major colony types (API Systems 20E and STAPH). Total aerobic bacterial counts were determined either on Brain-Heart-Infusion agar (Difco 0418) or Trypticase soy agar (Oxoid CM 131), supplemented with 0.3% lecithin and 1.0% Tween 80 to neutralize residual triclosan antimicrobial activity and also to facilitate growth of lipophilic coryneform bacteria. Coryneforms were selected on the same agar supplemented with 50 mg/l furoxone to suppress micrococci (6,7), Gram- negative bacteria on MacConkey agar (Difco 0075019), and Pseudomonas sp. on Pseu- dosel agar (BBL 11554) containing 300 mg/l cetrimide. Axillae isolates were cultured in Brain-Heart-Infusion broth (Oxoid CM 225), supplemented when necessary with 1% Tween 80 for lipophilic types. All microbiological studies were conducted on male subjects with unshaved axillae. Axillae population following aerosol spray treatment. ß Aerosol sprays were manufactured containing either 0, 0.05%, or 0.2% triclosan. The sprays, based on ethanol and containing 0.75% isopropyl-myristate as emollient, utilized a 50:50 mix of Freon 11/12 as propellant. After one week's preconditioning period with placebo soap, both axillae of six subjects were washed for 1 min with placebo soap, dried, and deodorant applied by spraying at a distance of 10 cm from the skin for a period of 3 sec. Total aerobic bacterial counts in the axillae were determined before and 1, 4, 7, and 9 h following treatment. Application and sampling were re- peated for an additional two days. Following additional conditioning periods with pla- cebo soap, the treatment and sampling regime was repeated with the other two aerosol formulations. ß In a subsequent study the influence of six months ad lib usage of triclosan-containing aerosol sprays on the number, composition, and sensitivity of bacteria present in the axillae was determined. Two groups, each of eight subjects, applied a marketed de- odorant spray (alcohol-based, containing 0.15% triclosan) or antiperspirant deodorant spray (aluminum chlorhydrate-based, containing 0.25% triclosan) at least once daily to both axillae, with bacteria sampling 4 h after treatment, during a one-week precondi- tioning period, i.e., using placebo soap only and following 1 day, 2 days, 5 days, 2 weeks, 4 weeks, 12 weeks, and 6 months usage of the deodorants. Sensitivity of axillae isolates to triclosan was examined by the agar incorporation method: Prepared plates of Brain-Heart-Infusion agar incorporating triclosan levels in the range 0. 001 mg/1 to 200 mg/1 were surface-inoculated with one drop of a 48-hour-old broth culture of the iso- late, diluted to approx. 10 7 cells/ml in sterile physiological saline. Following incuba- tion of the plates for 2-4 days at 37øC, the minimum inhibitory concentration (MIC) of triclosan for each axillae isolate was determined.