Organic and aqueous solvent extracts and fractions of Micromeria nervo
sa (Desf.) Benth. (Labiatae) were investigated for antimicrobial activ
ities on several microorganisms including bacteria and yeast. The diff
erent extracts differed significantly in their antimicrobial activitie
s with the ethanolic extract being most active, followed by ethyl acet
ate and petroleum ether extracts. The least active extract was the aqu
eous. No significant difference between the different test microorgani
sms in their susceptibility to different extracts, with Candida albica
ns being the most susceptible to ethanolic extract giving 1.5 times th
e effect of nystatin. One of the main active ingredients of M. nervosa
was isolated and identified as carvacrol. No significant difference i
n antimicrobial activity was found between carvacrol and its isomer th
ymol. The most susceptible test microorganism was Proteus vulgaris to
carvacrol, and P. vulgar is and C. albicans to thymol. The least susce
ptible bacterium to both fractions was Pseudomonas aeruginosa. Minimum
inhibitory concentration (MIG) and minimum bactericidal or fungicidal
concentrations (MBC or MFC) were determined for both compounds. (C) 1
997 Elsevier Science Ireland Ltd.