Open Access Open Badges Research article

Assessing the antibiotic potential of essential oils against Haemophilus ducreyi

Zachary Lindeman, Molly Waggoner, Audra Batdorff and Tricia L Humphreys*

Author Affiliations

Allegheny College Department of Biology, 520 N. Main St., Meadville, PA 16335, USA

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BMC Complementary and Alternative Medicine 2014, 14:172  doi:10.1186/1472-6882-14-172

Published: 27 May 2014



Haemophilus ducreyi is the bacterium responsible for the genital ulcer disease chancroid, a cofactor for the transmission of HIV, and it is resistant to many antibiotics. With the goal of exploring possible alternative treatments, we tested essential oils (EOs) for their efficacy as antimicrobial agents against H. ducreyi.


We determine the minimum inhibitory concentration (MIC) of Cinnamomum verum (cinnamon), Eugenia caryophyllus (clove) and Thymus satureioides (thyme) oil against 9 strains of H. ducreyi using the agar dilution method. We also determined the minimum lethal concentration for each oil by subculturing from the MIC plates onto fresh agar without essential oil. For both tests, we used a 2-way ANOVA to evaluate whether antibiotic-resistant strains had a different sensitivity to the oils relative to non-resistant strains.


All 3 oils demonstrated excellent activity against H. ducreyi, with MICs of 0.05 to 0.52 mg/mL and MLCs of 0.1-0.5 mg/mL. Antibiotic-resistant strains of H. ducreyi were equally susceptible to these 3 essential oils relative to non-resistant strains (p = 0.409).


E. caryophyllus, C. verum and T. satureioides oils are promising alternatives to antibiotic treatment for chancroid.

Haemophilus ducreyi; Chancroid; Essential oil