BACKGROUND OF THE INVENTION 
     The odorous compounds of plants are volatile and are usually separated from the plant material by steam distillation. They are known as the volatile or essential oils, and consist of hydrocarbons, alcohols, ethers aldehydes and ketones. In the evaluations of conifers and in the oils from citrus fruits and from eucalyptus trees, alicyclic hydrocarbons of the composition C 10  H 16  were found to be especially abundant, and it is to these compounds that the term &#34;terpene&#34; was applied in the restricted sense. It soon became evident, however, that compounds containing 15, 20, 30 and 40 carbon atoms also are closely related to terpenes, and the term &#34;terpene&#34; in its broadest sense now includes all such compounds, which comprise repeating iso-C 5  units. 
     Many of the essential oils are employed in various flavors and fragrances, and their medicinal or biocidal potential has been the subject of continued investigation. For example, the cyclic terpenones, α-ionone and β-ionone, were reported to exhibit moderate antibacterial activity against S. mutans by I. Kubo et al., J. Agric. Food Chem., 41, 2447 (1993). This bacterium is responsible for causing dental caries. Carvone, the chief component of spearmint oil, was reported to exhibit antifungal activity by V. Moleyar et al., Food Microbiol., 3, 331 (1986). Kubo et al., J. Natural Products, 57, 9 (1994) subsequently reported that a number of cyclic and acyclic terpene alcohols, including geranylacetol, farnesol and farnesyl acetol, exhibited activity against Pr. acnes, the bacterium responsible for acne. However, the linear ketone derived from farnesylacetol, farnesylacetone, was found to be inactive. 
     While some of these natural products may be potent enough for practical use, the synthesis or extraction of highly branched cyclic or alicyclic terpenes can be complex. Furthermore, terpenes such as ionone, a component of cedar oil, can cause allergic skin reactions. Nonetheless, essential oils and other phytochemicals are by definition biodegradable and renewable. Therefore, a continuing need exists for compounds of natural origin which exhibit useful levels of biocidal activity. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method to inhibit the growth of microorganisms, particularly microorganisms that are responsible for mammalian skin pathologies, comprising contacting the microorganisms with an effective growth-inhibiting amount of a 3-alken-2-one of the general formula (I): ##STR1## wherein n is 6-16 and X═Y═H or X and Y together are a covalent bond. Preferably n is 5-11 and X═Y═H, or n is 6-10 and X and Y together are a covalent bond. Preferably the 3,4-double bond is in the E- or trans-configuration. 
     Thus, the present invention also provides a composition adapted for topical application to the skin comprising an effective antimicrobial amount of at least one compound of formula (I), in combination with a dermatologically acceptable carrier. Preferred compositions in accord with the present application are therapeutic compositions adapted for topical application, as to the skin of a mammal afflicted with, or at risk of affliction with, a pathology associated with a microorganism such as a bacterium, a yeast or a fungus. Novel compounds of formula (I) are also within the scope of the invention, including 3-hexadecen-2-one. 
     The term &#34;skin&#34; as used herein is to be construed broadly, to include the epidermis, the lips, the scalp, the epithelium of the eye, the surfaces of body cavities, including the mouth, ear, nose, vagina, anus and the like, and the surfaces of wounds or lesions in the skin. The term &#34;antimicrobial&#34; or &#34;inhibit,&#34; as used with respect to the growth of microorganisms, is defined to encompass both complete inhibition (killing) of the microbes, as well as significant inhibition in growth or sporulation, as determined by the assays described herein, or by other standard assays, such as those disclosed by A. M. Janssen et al., Planta medica, 53, 395 (1987). Thus, the term &#34;antimicrobial&#34; encompasses the use of the present compounds in deodorant compositions, to control body odor, as well as in therapeutic compositions. All percentages are by weight unless otherwise noted. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A. Preparation 
     The 3-alken-2-ones of the present invention which are not commercially available, or which are novel compounds can be prepared by a number of methods available to the art. For example, 3-alken-2-ones of general formula RCH═CH-C(O)-CH 3  can generally be prepared by the crossed aldol condensation of acetone and the alkanal (RCHO), followed by the acid-catalyzed elimination of water from the resultant hydroxy ketone. See, for example, B. V. Burger et al., J. Chem. Ecol., 16, 397 (1990) (3-dodec-2-one) and G. Tishenko et al., J. Gen. Chem. USSR, 33, 134 (1963) (3-nonen-2-one). Alternatively, they can be prepared by the Wittig or Wittig-Horner reaction. 
     Y. -Z. Huang et al., Synth. Commun., 19, 501 (1989) have also reported a general synthesis of 2-alken-2-ones (trans-RCH═CHC(O)CH 3 ) by the reaction of the aldehyde (RCHO) with α-bromoacetone in the presence of tri-n-butylstibine for 1-16 hr at 25°-50° C., and prepared compounds wherein R is n-C 4  H 9 , n-C 8  H 17  or n-C 11  H 23 . The 3-alken-2-one wherein R is n-C 13  H 26  has been reported by R. Kazlauskas et al., Aust. J. Chem., 33, 2097 (1980). 
     The 3-alkene-2-one wherein R is C 7  H 15  has been reported by H. A. Palma-Fleming et al., Phytochem., 22, 1503 (1983). The 3-aken-2-one wherein R is C 9  H 19 , was prepared by A. A. Croteau et al., Tet. Letters, 24, 2481 (1983), who report a general synthesis of E/Z mixtures of 3-alken-2-ones by the condensation of lithiated α-silylketimine (Me 3  Si-CHLi-C(═Nt-Bu)Me) with RCHO, followed by hydrolysis. Also, the preparation of (Z)-3-alken-2-ones by the condensation of alkenyl lithiocuprates with acetyl halides has been reported by N. Jabri et al., Tetrahedron, 42, 1369 (1986). The preparation of 3-tetradecen-2-one (R═C 10  H 21 ) has been reported by J. Kang et al., Bull. Korean Chem. Soc., 15, 306 (1994). 
     B. Bioactivity 
     The present compounds and compositions comprising them can be employed in a wide range of antimicrobial applications, including surface disinfecting, and for treating foods such as fruits and seeds. The present compounds are particularly useful to inhibit the growth of pathological microorganisms, such as bacteria, fungi and yeasts on the skin of humans and of animals such as household pets, farm animals and zoo animals. Such grampositive microorganisms include Propionibacterium acnes which is the primary pathogen which causes human acne vulgaris, and the streptocci and staphylococci which cause impetigo. Mycotic infections of animals and humans can also be treated, including tinea capitis, tinea cruris (jock itch), tinea corporis (ringworm), tinea pedis (athlete&#39;s foot) and tinea unguium. Fungi associated with such dermatophytosis include T. mentagrophytes, M. audevinii, T. rubrum, E. floccosum, M. pelineum and Candida albicans. 
     The present compounds are also effective against fungi associated with infections of the membranes of body cavities. Such infections include thrush, vaginitis and paronychia. See R. T. Yousef et al., Mykosen, 21, 190 (1978) and H. Gershon, J. Pharm. Sci., 68, 82 (1979). The present compounds can also be used in cosmetic and skin-cleansing compositions such as soaps, shampoos, deodorants, and skin softening lotions, where they can function as deodorants, i.e., to control odor-causing bacteria on the skin. The present compounds can also be employed in dentifrices, chewing gums, and mouthwashes to inhibit the growth of Streptococcus mutans, which is a causative agent for dental caries, and in shampoos, rinses, and other haircare products, to inhibit Pityrosporum ovale (dandruff, skin lesions in immune-suppressed subjects). Infections due to Staphylococcus aureus are also susceptible to these compounds. 
     C. Compositions. 
     Although in some instances, the present compounds may be administered in pure form, i.e., when they are liquids, it will generally be desirable to administer them to the skin as compositions or formulations, in combination with a dermatologically acceptable carrier, which may be a solid or a liquid. 
     Useful solid carriers include finely divided solids such as talc, clay, microcrystalline cellulose, silica, alumina and the like. Useful liquid carriers include water, alcohols or glycols or water-alcohol/glycol blends, in which the present compounds can be dissolved or dispersed at effective levels, optionally with the aid of non-toxic surfactants. Adjuvants such as flavorings, fragrances and additional antimicrobial agents can be added to optimize the properties for a given use. The resultant liquid compositions can be applied from absorbent pads, used to impregnate bandages and other dressings, or sprayed onto the affected area using pump-type or aerosol sprayers. The liquid compositions can also be employed as eyedrops, mouth washes, douches, etc. Antibacterial presaturated wipes are disclosed by Anderson (U.S. Pat. No. 4,896,768). 
     Thickeners such as synthetic polymers, fatty acids, fatty acid salts and esters, fatty alcohols, modified celluloses or modified mineral materials can also be employed with liquid carriers to form spreadable pastes, gels, ointments, soaps, and the like, for application directly to the skin of the user. 
     The total concentration of one or more compounds of formula (I) in the present compositions can be varied widely, and will depend on factors such as the compatibility of the active ingredient(s) with the vehicle, the potency of the active ingredient(s) and the condition to be treated. Generally, the concentration of the compound(s) of formula (i) in a liquid composition, such as a lotion, will be from about 0.1-25 wt-%, preferably from about 0.5-10 wt-%. The concentration in a semi-solid or solid composition such as a gel or a powder will be about 0.1-5 wt-%, preferably about 0.5-2.5 wt-%. 
     The present compounds of formula (I) are particularly useful to treat human or animal acne by topical application, as gels, ointments, lotions, soaps, and the like. For a further discussion of the pathology and etiology of acne, and of the formulation of aqueous cream and gel vehicles as carriers for other agents used to treat acne, see Klein et al. (U.S. Pat. No. 4,692,329). The total dosage delivered will depend on the extent of the infected area to be treated, the severity of the infection and the number of applications, as determined by the subject&#39;s dermatologist, physician or veterinarian. 
     The present invention will be further described by reference to the following detailed examples. 
     EXAMPLE 1 
     Synthesis of (E)-3-Alken-2-ones and (E)-3,13-Tetradecadien-2-one 
     To 5.0 g of piperidine, 5.0 g of glacial acetic acid and. 250 mL of acetone at reflux in a 500 mL round-bottomed flask was added 0.10 mole of one of the following aldehydes (octanal, nonanal, decanal, undecanal, 10-undecenal, dodecanal, tridecanal, or tetradecanal) in 50 mL of acetone dropwise over 0.5 hours. After addition, the solution was refluxed for an additional 5 hours. The acetone was removed in vacuo and the residue was placed in 50 mL of diethyl ether. The ether solution was washed with 2×50 mL water, 2×50 mL 1M HCl and 2×50 mL saturated NaHCO 3 . The ether solution was dried with anhydrous CaCl 2  and the ether was removed in vacuo. A pure sample of each compound was obtained by preparative gas chromatography. 
     EXAMPLE 2 
     Spectral Data for (E)-3-Alken-2-ones and (E)-3,13-Tetradecadien-2-one 
     Mass spectra of the following compounds were recorded on a Hewlett-Packard gas chromatograph (Model 5890) fitted with a mass selective detector (Model 5970) using a 12 m cross-linked methyl silicone capillary column. The gas chromatograph was programmed so the oven temperature was kept at 40° C. for 4 minutes, then increased to a final temperature of 250° C. at a rate of 30° C./min and kept at this temperature for four minutes. Mass spectral fragments below m/z=35 were not recorded. The mass selective detector was tuned using perfluorotributylamine and the internal computer tuning program. 
     The  1  H and  13  C NMR spectra of the compounds were recorded at 300 MHz and 75 MHz respectively on Bruker QE plus. Samples were dissolved in CDCl 3 , and chemical shifts are given in ppm relative to tetramethylsilane (TMS) at zero ppm using the solvent peak a 77.0 ppm as the internal standard. The synthetic 3-alken-2-ones and 3,13-tetradecadien-2-one were shown to be the (E)-isomer by the  1  H-NMR coupling constant of 15.9 Hz for the olefinic protons. 
     A. (E)-3-Undecen-2-one (1). 300 MHz  1  H-NMR (CDCl 3 )δ=6.78(dt,1H,J=15.9 Hz,6.9 Hz), 6.03(dt, 1H,J=15.9 Hz,J=1.48 Hz), 2.21(s,3H), 2.19(quart,2H), 1.44(m,2H), 1.26(m,8H) and 0.85(t,3H); 75 MHz  13  C-NMR (CDCl 3 ) δ=198.74, 148.68, 131.29, 32.50, 31.75, 29.17, 29.08, 28.12, 26.82, 22.65, 14.09; and E1-MS m/z=97(7), 83(5), 81(6), 71(15), 69(18), 68(6),55(50). 43(100), 41(40) and 39(19). 
     B. (E)-3-Dodecen-2-one (2). 300 MHz  1  H-NMR (CDCl 3 ) δ=6.73(dt,1H,J=15.9 Hz,6.9 Hz), 5.99(dt,1H,J=15.9 Hz,J=1.48 Hz), 2.18(s,32.15(quart,2H), 1.38(m,2H), 1.21(m, 10H) and 0.81(t,3H); 75 MHz  13  C-NMR (CDCl 3 ) δ=198.80, 148.72, 131.31, 32.53, 31.87, 29.39, 29.23, 28.13, 26.84, 22.69, and 14.13; and E1-MS m/z=97(15), 83(11), 82(9), 81(8), 71(25), 69(18), 55(50), 43(100), 41(37) and 36(18). 
     C. (E)-3-Tridecen-2-one (3). 300 MHz  1  H-NMR (CDCl 3 ) δ=6.81(dt, 1H,J=15.9 Hz,6.9 Hz), 6.06(dt, 1H,J=15.9 Hz,J=1.48 Hz), 2.24(s,3H), 2.22(quart,2H), 1.46(m,2H), 1.26(m, 12H) and 0.88(t,3H); 75 MHz  13  C-NMR (CDCl 3 ) δ=198.80, 148.69, 131.24, 32.47, 31.85, 29.46, 29.37, 29.27, 29.17, 28.07, 26.79, 22.65, and 14.09; E1-MS m/z=196(M + ,2), 181(8), 97(31), 96(14), 83(22), 81(20), 71(34), 69(31), 55(65), 43(100), 41(44); and FT-IR (neat) 2925, 2854, 1700, 1677, 1628, 1467, 1360, 1253, 1189 and 980 cm -1 . 
     D. (E)-3-Tetradecen-2-one (4). 300 MHz  1  H-NMR (CDCl 3 ) δ=6.79(dt,1H,J=15.9 Hz,6.9 Hz), 6.05(dt,1H,J=15.9 Hz,J=1.48 Hz), 2.23(s,3H), 2.21(quart,2H), 1.45(m,2H), 1.26(m, 14H) and 0.87(t,3H); 75 MHz  13  C-NMR (CDCl 3 ) δ=198.79, 148.71, 131.31, 32.53, 31.94, 29.62, 29.57, 29.43, 29.36, 29.23, 28.13, 26.84, 22.72, and 14.15; E1-MS m/z=97(21), 84(9), 83(8), 81(12), 71(30), 69(18), 55(50), 43(100), 41(50) and 39(18). 
     E. (E)-3,13-Tetradecadien-2-one (5). 300 MHz  1  H-NMR (CDCl 3 ) δ=6.80(dt,1H,J=15.9 Hz,6.9 Hz), 6.06(dt,1H,J=15.9 Hz,J=1.48 Hz), 5.80(m,1H), 4.95(m,2H), 2.24(s,3H), 2.22(quart,2H), 2.03(quart,2H), 1.46(m,2H) and 1.28(m, 10H); 75 MHz  13  C-NMR (CDCl 3 ) δ=198.83, 148.71,139.18, 131.32, 114.20, 33.83, 32.52, 29.38, 29.21, 29.12, 28.94, 28.13, 26.87; E1-MS m/z=97(20), 95(14), 81(21), 71(19), 69(17), 67(23), 55(59), 43(100), 41(71) and 39(35). 
     F (E)-3-Pentadecen-2-one (6). 300 MHz  1  H-NMR (CDCl 3 ) δ=6.80(dt, 1H,J=15.9 Hz,6.9 Hz), 6.05(dt, 1H,J=15.9 Hz,J=1.48Hz), 2.23(s,3H), 2.21(quart,2H), 1.46(m,2H), 1.26(m, 16H) and 0.88(t,3H); 75 MHz  13  C-NMR (CDCl 3 ) δ=198.79, 148.71, 131.31, 32.53, 31.96, 29.66, 29.57, 29.44, 29.38, 29.33, 29.24, 28.14, 26.85, 22.73, and 14.16; E1-MS m/z=97(18), 84(10), 81(11), 71(28), 69(16), 68(10), 67(10), 55(46), 43(100), and 41(40). 
     G. (E)-3-Hexadecen-2-one (7). 300 MHz  1  H-NMR (CDCl 3 ) δ=6.80(dt,1H,J=15.9 Hz,6.9 Hz), 6.06(dt,1H,J=15.9 Hz,J=1.48 Hz), 2.24(s,3H), 2.22(quart,2H), 1.47(m,2H), 1.26(m,18H) and 0.88(t,3H); 75 MHz  13  C-NMR (CDCl 3 ) δ=198.83, 148.74, 131.31, 32.54, 31.97, 29.71, 29.68, 29.58, 29.54, 29.44, 29.41, 29.25, 28.15, 26.85, 22.74, and 14.17; E1-MS m/z=97(18), 84(8), 83(8), 82(8), 81(9), 71(30), 69(15), 55(42), 43(100), and 41(50). 
     H. (E)-3-Heptadecen-2-one (8). 300 MHz  1  H-NMR (CDCl 3 ) δ=6.80(dt,1H,J=15.9 Hz,6.9 Hz), 6.07(dt,1H,J=15.9 Hz,J=1.48 Hz), 2.24(s,3H), 2.22(quart,2H), 1.47(m,2H), 1.26(m,20H) and 0.88(t,3H); 75 MHz  13  C-NMR (CDCl 3 ) δ=198.83, 148.74, 131.32, 32.54, 31.97, 29.70, 29.58, 29.44, 29.41, 29.34, 29.25, 28.15, 26.87, 22.74, and 14.18; and E1-MS m/z=252 (M+, 3), 97(19), 84(8), 83(10), 81(11), 71(28), 69(14), 55(39), 43(100), and 41(50). 
     EXAMPLE 3 
     Bioassays 
     The microorganisms tested were from the American Type Culture Collection (Rockville, Md.). They are Bacillus subtilis ATCC 9372, Brevibacterium ammoniagenes ATCC 6872, Staphylococcus aureus ATCC 12598, Streptococus mutans ATCC 25175, Propionibacterium acnes ATCC 11827, Pseudimonas aeruginosa ATCC 10145, Enterobacter aerogenes ATCC 13048, Eschericia coli ATCC 9637, Proteus vulgaris ATCC 133315, Saccharomyces cerevisiae ATCC 7754, Candida utilis ATCC 9226, Pityrosporum ovale ATCC 14521, Penicillium chrysogenum ATCC 10106 and Trichophyton mentagrophytes ATCC 18748. 
     The bacterial culture media except for S. mutans was 0.8% nutrient broth (BBL), 0.5% yeast Extract (Difco) and 0.1% glucose (NYG broth). S. mutans was cultured in 3.7% brain heart infixsion broth (Difco). All fungi, except P. ovale and T. mentagrophytes were cultured in a 2.5% malt extract broth (BBL). P. ovale was cultured in 1% bactopeptone (Difco), 0.5% yeast extract, 1% glucose and 0.1% corn oil. For T. mentagrophytes the culture media was 1% bactopeptone and 4% glucose. 
     Freeze dried samples were prepared for testing as follows. B. subtilis, S. cerevisiae, C. utilis, and P. ovale, were shake-cultured for two days at 30° C. P. chrysogenum and T. mentagrophytes were shake-cultured for 5 days at 30° C. B. ammoniagenes and E. aerogenes were stationarily cultured at 30° C. S. aureus, S. mutans, P. acnes, P. aeruginosa, E. coli and P. vulgaris were stationarily cultured at 37° C. 
     The minimum inhibitory concentration (MIC) of the 3-alken-2-ones (compounds 1-4, 6-8) and 3,13-tetradecadien-2-one (compound 5) was performed using a two-fold serial broth dilution. Each test compound was dissolved in DMF and 30 μL of this sample was dissolved in 3 mL of the applicable medium. A 30 μL sample of the previously described culture of each microorganism was added to the various medium solutions. After two days, the cultures of B. subtilis, S. cerevisiae, C. utilis B. ammoniagenes, E. aerogenes, S. aureus, S. mutans, P. acnes, P. aeruginosa, E. coli and P. vulgaris were examined for turbidity (OD at 660 nm). The fungi, P. ovale, P. chrysogenum and T. mentagrophytes, were examined visually for growth at 3 days (P. ovale) and 5 days (P. chrysogenum and T. mentagrophytes). The MIC was determined as the lowest concentration for each compound that no growth was observed. The highest concentration used in these tests was 800 μg/mL. 
     
                                           TABLE 1__________________________________________________________________________MIC of (E)-3-Alken-2-ones and (E)-3,13-tetradecadien-2-one (μg/mL)               Compound TestedOrganism            1    2    3   4   5   6   7   8__________________________________________________________________________Bacillus subtilis ATCC 9372               100  100   100                             &gt;800                                 &gt;800                                     &gt;800                                         &gt;800                                             &gt;800Brevibacterium ammoniagenes ATCC 6872               200  100   100                             &gt;800                                 &gt;800                                     &gt;800                                         &gt;800                                             &gt;800Staphylococcus aureus ATCC 12598               200  100    50                             &gt;800                                 &gt;800                                     &gt;800                                         &gt;800                                             &gt;800Streptococus mutans ATCC 25175               100   50    25                               25                                   25                                      200                                          400                                              800Propionibacterium acnes ATCC 11827                50   25  12.5                             12.5                                 12.5                                     6.25                                         3.13                                             3.13Pseudimonas aeruginosa ATCC 10145               &gt;800 &gt;800 &gt;800                             &gt;800                                 &gt;800                                     &gt;800                                         &gt;800                                             &gt;800Enterobacter aerogenes ATCC 13048               &gt;800 &gt;800 &gt;800                             &gt;800                                 &gt;800                                     &gt;800                                         &gt;800                                             &gt;800Eschericia coli ATCC 9637               &gt;800 &gt;800 &gt;800                             &gt;800                                 &gt;800                                     &gt;800                                         &gt;800                                             &gt;800Proteus vulgaris ATCC 133315                50   50   800                             &gt;800                                 &gt;800                                     &gt;800                                         &gt;800                                             &gt;800Saccharomyces cerevisiae ATCC 7754               800  800  &gt;800                             &gt;800                                 &gt;800                                     &gt;800                                         &gt;800                                             &gt;800Candia utilis ATCC 9226                50  400  &gt;800                             &gt;800                                 &gt;800                                     &gt;800                                         &gt;800                                             &gt;800Pityrosporum ovale ATCC 14521               100  100   100                              100                                  200                                      400                                         &gt;800                                             &gt;800Penicillium chrysogenum ATCC 10106               100  100   800                              800                                  800                                     &gt;800                                         &gt;800                                             &gt;800Trichophyton mentagrophytes ATCC 18748               100  100    25                             12.5                                 12.5                                      800                                         &gt;800                                             &gt;800__________________________________________________________________________ 
    
     As demonstrated by the data summarized in Table 1, the greatest activity observed with compounds 1-8 occurred against P. acnes, the primary pathogen responsible for causing human acne. Compounds 1-5 also exhibited substantial activity against T. mentagrophytes, the causative agent of athlete&#39;s foot and compounds 1-7 inhibited Streptococcus mutans (dental caries). Compounds 1-6 also exhibited somewhat lesser activity against P. ovale (dandruff) and compounds (1)-(3) were active against S. aureus and Proteus vulgaris. Specifically, (E)-3-tridecen-2-one (3), showed activity against all of the grampositive bacteria (B. subtilis, B. ammoniagenes, S. aureus, S. mutans, and P. acnes) in the test. It was most active against P. acnes, having a minimum inhibitory concentration (MIC) of 12.5 μg/mL. This compound was not active against the gram-negative bacteria, P. aeruginosa, E. aerogenes and E. coli. Activity against yeast was mixed, no activity was seen against S. cerevisiae and C. utilis, although P. ovale showed moderate inhibition. Weak activity was seen with fungi P. chrysogenum, while the fungi T. mentagrophytes had a MIC of 25 μg/mL. 
     (E)-3-tetradecen-2-one (4), showed activity against some gram-positive bacteria (S. mutans, and P. acnes) in the test. It was most active with P. acnes having a minimum inhibitory concentration (MIC) of 12.5 μg/mL. This compound was not active against the gram-negative bacteria, P. aeruginosa, E. aerogenes and E. coli. Activity against yeast was mixed, no activity was seen against S. cerevisiae and C. utilis, although P. ovale showed moderate inhibition. Weak activity was seen with fungi P. chrysogenum, while the fungi T. mentagrophytes had a MIC of 12.5 μg/mL. 
     The synthetic products, (E)-3-hexadecen-2-one (7) and (E)-3-heptadecen-2-one (8), were inactive to all of the bacteria and fungi in the test, except S. mutans and P. acnes. With S. mutans (7) was weakly active, but (7) and (8) exhibited strong activity (3.13 μg/mL) against P. acnes. 
     EXAMPLE 4 
     A powder composition may be prepared having the following formulation: 
     
         ______________________________________        Per Canister______________________________________Compound 4          1.0     gTalc                99      g______________________________________ 
    
     EXAMPLE 5 
     A lotion composition may be prepared having the following formulation: 
     
         ______________________________________         Per Canister______________________________________Compound 7           1.0     gCetyl Alcohol        25      gGlyceryl Stearate    25      gGlycerol             20      gWater                10      gStearyl Alcohol      10      g______________________________________ 
    
     EXAMPLE 6 
     A lotion composition may be prepared having the following formulation: 
     
         ______________________________________         Per Canister______________________________________Compound 7           0.5     gCompound 4           0.5     gCetyl Alcohol        25      gGlyceryl Stearate    25      gGlycerol             20      gWater                10      gStearyl Alcohol      10      g______________________________________ 
    
     Other examples of useful dermatological compositions which can be used to deliver the compounds of claim 1 to the skin are disclosed in Jacquet et al. (U.S. Pat. No. 4,608,392), Geria (U.S. Pat. No. 4,992,478), Smith et al. (U.S. Pat. No. 4,559,157) and Wortzman (U.S. Pat. No. 4,820,508). 
     All publications and patents are incorporated by reference herein, as though individually incorporated by reference. The invention has been described with reference to various specific and preferred embodiments and techniques. However, it should be understood that many variations and modifications may be made while remaining within the spirit and scope of the invention.
A method to inhibit microbial growth is provided comprising topically administering to a mammal afflicted with a pathology associated with microbial growth, such as a dermatological condition, an effective amount of a linear (C 12 -C 22) 3-alken-2-one or 3,o-alkadien-2-one.