Brewer and Lilley1, 2 reported the addition of phenylethanol to a nutritive medium permitted growth of Gram-positive organisms, but markedly to completely inhibited growth of Gram-negative organisms. Phenylethanol Agar inhibits swarming of Proteus spp., and can be used to selectively isolate anaerobic bacteria from clinical specimens with mixed flora. Phenylethanol Agar is specified for use in several reference methods.3,4 The nitrogen, vitamin, and carbon sources are provided by enzymatic digest of casein and enzymatic digest of soybean meal. Sodium Chloride maintains the osmotic balance of the medium. Phenylethanol is bacteriostatic for Gram-negative bacteria and inhibits DNA synthesis. Agar is the solidifying agent. The addition of 5% defibrinated sheep blood to the basal medium can enhance microorganism recovery of the medium.
1. Brewer, J. H., and B. D. Lilley. 1949. Paper presented at the December meeting of the Maryland Association of Medical and Public Health Laboratories.
2. Lilley, B. D., and J. H. Brewer. 1953. The selective antibacterial action of phenylethylalcohol. J. Pharm. Assoc. 42:6.
3. Murray, P. R., E. J. Baron, M. A. Pfaller, F. C. Tenover, and R. H. Yolken (eds.). 1995. Manual of clinical microbiology, 6th ed. American Society of Microbiology, Washington, D.C.
4. Isenberg, H. D. 1992. Clinical microbiology procedures handbook, American Society for Microbiology, Washington, D.C.
5. Washington, J. A., Jr. 1981. Laboratory procedures in clinical microbiology. Springer-Verlag, New York.
6. Casman, E. P. 1947. A noninfusion blood agar base for neisseriae, pneumococci and streptococci. Am. J. Clin. Pathol. 17:281-289.
7. MacFaddin, J. F. 1985. Media for the isolation-cultivation-identification-maintenance of medical bacteria, vol. 1 Williams & Wilkins, Baltimore, MD.