Antimicrobial activity of some Argentinean wild plant essential oils against Paenibacillus larvae larvae, causal agent of American foulbrood (AFB)

Abstract

SummaryFive essential oils from Argentinan wild plants were tested in vitro for antimicrobial activity against different strains of Paenibacillus larvae larvae, causal agent of American foulbrood in honey bees, Apis mellifera L. The species selected from which to extract the essential oils were aguaribay (Schinus molle var. areira L), Andean thyme (Acantholippia seriphioides A. Gray), peperine (Mintosthachys mollis H.B.K. Gris), camomile (Tagetes minuta L.) and pennyroyal (Lippia turbinata Griseb.). Oils were extracted from different parts of the plants by steam distillation. Minimal inhibitory concentration (MIC) and minimal bactericide concentration (MBC) were evaluated on Mueller-Hinton broth and on MYPGP agar respectively, by the tube dilution method. MIC and MBC minimum and maximum values obtained were 200–250 mgL−1 and 200–300 mgL−1 for Andean thyme and 800–1000 mgL−1 and 850–1100 mgL−1 for pennyroyal, respectively. The other oils had intermediate MIC and MBC values between the formers mentioned. Highly significant differences between MIC and MBC values for the essential oils tested were found. Tukey's mean separation test indicated that Andean thyme (A. seriphioides) essential oil was different from the other four essential oils at α<0.01. Andean thyme proved to be the most effective in vitro essential oil against P. larvae larvae. Therefore, it may be a promising natural alternative to traditional antibiotics, meriting further studies on its field applicability for AFB control.