Resumen de In vitro antibacterial effect of exotic plants essential oils on the honeybee pathogen Paenibacillus larvae, causal agent of American foulbrood

Sandra R. Fuselli, S.B. García de la Rosa, M.J. Eguaras, R. Fritz

• español

  Se determino la composicion quimica y se evaluo la actividad antimicrobiana in vitro de cuatro aceites esenciales de plantas exoticas para el control del patogeno bacteriano Paenibacillus larvae, agente causal de loque americana, que afecta a los estadios de larva y pupa de la abeja melifera (Apis mellifera L.). Esta enfermedad produce grandes perdidas economicas en la apicultura mundial. Los aceites esenciales analizados, pertenecientes a la familia Myrtaceae y Gramineae, fueron: niaouli (Melaleuca viridiflora) y arbol del te (Melaleuca alternifolia), citronela (Cymbopogon nardus) y palmarosa (Cymbopogon martinii), respectivamente. La composicion quimica de los aceites esenciales se efectuo por cromatografia de gases acoplada a un espectrometro de masas (CG-EM). La concentracion inhibitoria minima (MIC) se determino por el metodo de microdilucion en caldo y la concentracion bactericida minima (MBC) en agar MYPGP. Los aceites esenciales de niaouli y citronela registraron valores promedio de MIC de 320 mg L.1, atribuidos al tipo y porcentaje de sus componentes: terpinen-4-ol (29,09%), �¿-pineno (21,63%) y limoneno (17,4%) que predominaron en M.

  viridiflora, mientras que el limoneno (24,74%), citronelal (24,61%) y geraniol (15,79%), constituyeron los componentes mayoritarios de C. nardus. El excesivo uso de antibioticos para el control de esta enfermedad ha generado fenomenos de resistencia y de contaminacion de todos los productos derivados de la colmena. El uso de estos aceites esenciales representa una alternativa de rotacion a los productos mundialmente utilizados en la quimioterapia de loque americana, constituyendo un aporte a la busqueda de metodos alternativos naturales para el control de esta enfermedad.

• English

  Chemical composition and antimicrobial activity of exotic plants essential oils to potentially control Paenibacillus larvae, the causal agent of American foulbrood disease (AFB) were determined. AFB represents one of the main plagues that affect the colonies of honeybees Apis mellifera L. with high negative impact on beekeepers worldwide. Essential oils tested were niaouli (Melaleuca viridiflora) and tea tree (Melaleuca alternifolia) from Myrtaceae, and citronella grass (Cymbopogon nardus) and palmarosa (Cymbopogon martinii) from Gramineae. The components of the essential oils were identified by SPME-GC/MS analysis. The antimicrobial activity of the oils against P. larvae was determined by the broth microdilution method. In vitro assays of M. viridiflora and C. nardus oils showed the inhibition of the bacterial strains at the lowest concentrations tested, with minimal inhibitory concentration (MIC) mean value about 320 mg L�1 for both oils, respectively. This property could be attributed to the kind and percentage of the components of the oils. Terpinen-4-ol (29.09%), á-pinene (21.63%) and limonene (17.4%) were predominant in M. viridiflora, while limonene (24.74%), citronelal (24.61%) and geraniol (15.79%) were the bulk of C. nardus. The use of these essential oils contributes to the screening of alternative natural compounds to control AFB in the apiaries; toxicological risks and other undesirable effects would be avoided as resistance factors, developed by the indiscriminate use of antibiotics.