Aromatic alcohols and their effect on Gram-negative bacteria, cocci and mycobacteria

Phenethyl alcohol (2-phenylethanol; PEA, mol. wt 122.17) inhibits a range of Gram-negative bacteria, but not Pseudomonas fluorescens, at a concentration of 0.2% (2000 mg/L), whereas Gram-positive cocci, such as Staphylococcus aureus are inhibited at 0.5% w/v (5000 mg/L), with Enterococcus faecalis requiring still higher concentrations.1 PEA-containing media had earlier been suggested as a means of selecting for Gram-positive bacteria in mixed flora.2 Interestingly, Mycobacterium smegmatis and Mycobacterium phlei were also inhibited at 0.2%, suggesting that the solubility of PEA in lipids could play a major role in its selective action.1 However, Wilson et al.3 reported that PEA was only slightly less inhibitory to Staphylococcus aureus than Escherichia coli, and that the MIC for Pseudomonas aeruginosa was 0.46% (4600 mg/L).