In vitro growth-inhibitory effect of Brazilian plants extracts against Paenibacillus larvae and toxicity in bees

Abstract

American foulbrood (AFB) is a serious worldwide spreading disease in bees caused by Paenibacillus larvae. Plants extracts are known to decrease or inhibit the growth of these bacteria. The purpose of this study was to evaluate the antimicrobial activity of Calendula. officinalis, Cariniana domestica, and Nasturtium officinale extracts against the P. larvae and to evaluate the toxicity of the extracts in bees. In vitro activity against P. larvae of the extracts was evaluated by micro dilution method and the minimal inhibitory concentrations (MICs) were also determined. The concentrations used in the toxicity test were established based on the MIC values and by the spraying application method. The P. larvae was susceptible to the evaluated crude extract of C. officinalis and N. officinale. To C. domestica, only the ethyl acetate (EtAc) fraction and n-butanol (BuOH) fractions had activity against P. larvae. Toxicity analysis in bees showed no toxicity for N. officinale crude extract and for C. domestica BuOH fraction during 15 days of treatment, however, some deaths of bees occurred during the first three days of treatment with C. officinalis and C. domestica EtAc fraction. The results with these species were firstly described and showed that N. officinale crude extract and C. domestica BuOH fraction both presented not toxic effects in the concentration tested by the spraying application method, and can be a useful alternative for treatment or prevention of AFB.

Honeybee health in South America

“…In Uruguay, the use of ethanolic extract of propolis on colonies has been a useful prevention strategy (Antúnez et al 2008). Currently, alternative strategies for the prevention and treatment of AFB are being studied, mainly based on essential oils (Fuselli et al 2010;Sabate et al 2012;Santos 844 et al 2012;Damiani et al 2014;González et al 2015;Piana et al 2015), probiotics (Audisio et al 2011), and propolis (Bastos et al 2008). …”

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“…Agentes patogênicos como ácaros, fungos, bactérias, vírus e parasitos são grandes ameaçadores da saúde das abelhas. Dessa forma, o controle de fatores como temperatura e umidade relativa deve ser considerado durante a instalação dos apiários, já que locais com alta umidade favorecem o aparecimento de fungos e doenças microbianas que influenciam diretamente no sucesso da atividade (Alves et al, 2015).…”

“…Larvae. Essa bactéria forma esporos que afetam as larvas e pupas das abelhas (Albo et al, 2003;Piana et al, 2015). Os esporos liberados pela bactéria penetram no intestino médio das larvas até entrar na cavidade do corpo, causando assim uma infecção que leva a larva a morte (Behrens et al, 2007).…”

“…Existem, no mundo, estudos em busca de plantas com substâncias antibacterianas. No Brasil, há uma rica biodiversidade com numerosos compostos que podem contribuir para a saúde das abelhas, dentre elas a Calendula officinalis, Cariniana domestica e Nasturtium officinale (Piana et al, 2015). Albo et al (2003) encontraram em seus estudos que pequenas concentrações de óleos essenciais de plantas aromáticas como tomilho (Thymus vulgaris), capim limão (Cymbopogon citratus), manjericão (Ocimum basilicum) e orégano (Origanum Vulgare) são eficientes no controle da loque americana, visto que reduzem os níveis de resistência da bactéria.…”

Protocols to test the activity of antimicrobial peptides against the honey bee pathogen Paenibacillus larvae

“…upon the current strategies used to control this disease and so alternative treatment strategies and/or prophylaxes for AFB are currently being investigated (Alvarado et al, 2013(Alvarado et al, , 2015Beims et al, 2015;Chan et al, 2009;Ghorbani-Nezami et al, 2015;Gonzalez et al, 2015;Oliveira et al, 2015;Piana et al, 2015).…”