Minimum inhibitory concentrations of herbal essential oils and monolaurin for gram-positive and gram-negative bacteria.

New, safe antimicrobial agents are needed to prevent and overcome severe bacterial, viral, and fungal infections. Based on our previous experience and that of others, we postulated that herbal essential oils, such as those of origanum, and monolaurin offer such possibilities. We examined in vitro the cidal and/or static effects of oil of origanum, several other essential oils, and monolaurin on Staphylococcus aureus, Bacillus anthracis Sterne, Escherichia coli, Klebsiella pneumoniae, Helicobacter pylori, and Mycobacterium terrae. Origanum proved cidal to all tested organisms with the exception of B. anthracis Sterne in which it was static. Monolaurin was cidal to S. aureus and M. terrae but not to E. coli and K. pneumoniae. Unlike the other two gram-negative organisms, H. pylori were extremely sensitive to monolaurin. Similar to origanum, monolaurin was static to B. anthracis Sterne. Because of their longstanding safety record, origanum and/or monolaurin, alone or combined with antibiotics, might prove useful in the prevention and treatment of severe bacterial infections, especially those that are difficult to treat and/or are antibiotic resistant.