Effect of systemic administration of essential oils and main components on honeybee survival

Controlling bee diseases with non contaminant products is a challenge in apicultural research. Essential oils and their main components have been widely studied as alternative treatments for honeybee pathologies [1, 2, 3]. However, there is little information about prolonged systemic administration. The aim of this study was to evaluate, in laboratory assays, the effect of long term consumption of essential oils and main components. Oils were obtained by hydrodistillation from Laurus nobilis, Cinnamomun zeylanicum, Origanum vulgare, Rosmarinus officinalis and Eucalyptus spp. and were analyzed by gas chromatography. The main components administered were 1,8-cineol, β-myrcene, cinnamic aldehyde, carvacrol and α-phellandrene. Substances were administered ad libitum to newly emerged bees at concentrations of 0; 333; 3,333 and 6,666 ppm, on sucrose syrup, throughout 11-18 days. Mortality and substances consumption were measured daily. Survival analysis was performed using Gehan-Breslow test and pairwise multiple comparisons between survival curves (a= 0, 05). Substances consumption was analyzed using one way ANOVA. Bees that received cinnamon oil showed a lower survival than control at concentrations higher than 333 ppm (pvalues<0.001 ). Consumption of cinnamic aldehyde, the main component of this oil (79.3%), also caused lower survival at the same concentrations (p-values<0.001). Eucalyptus oil caused a lower survival rate when it was administered at 6,666 ppm, although 1,8 cineol, its main component (63.5%), was not toxic for bees at any concentration. Carvacrol, a main component of many oregano essential oils, showed toxic effects at 3,333 and 6,666 ppm. Essential oils did not cause differences in consumption rate (p= 0.275) while main components solutions, except for carvacrol, were less consumed than control at the three concentrations. Treatments did not cause dysentery to bees. Our results contribute to understanding the effect of repeated systemic doses of these substances, which is important to design long term pharmacological studies and treatments development

Antimicrobial activity of essential oils against Paenibacillus larvae

American foulbrood is a serious bacterial disease that affects Apis mellifera colonies; the causative agent is Paenibacillus larvae [1 ]. The aim of the study was to evaluate in vitro the antimicrobial activity of 32 essential oils against P. larvae. Oils from 21 botanical species were analyzed by gas chromatography (CG and CG/EM). All essential oils were classified according to the composition of their main components in two groups: benzene ring compounds (BRC) and terpene compounds (TC). Minimal inhibitory concentration (MIC) in MYT broth [2] was assessed by the microdilution method. Final serial dilution concentrations of the essential oils ranged between 2,000-12.5 mgll. The bacterial isolates were collected from different Argentina's region. The chromatographic analysis showed that a 67% of the essential oils contained predominately terpene compounds. while the remaining 33% included mainly compounds with benzene rings. From the TC group, Cymbopogon citratus essential oil showed the better antimicrobial activity against P. larvae with MIC values between 150 and 250 mgl l. The essential oi ls from Aloysia polystachya and Mentha spp. had the lowest inhibitory activity. Among the oils from the BRC group, one of the lowest MIC values was found with cinnamon essential oil (Cinnamomun zeylanicum) being between 25 and 50 mg/L; Origanum vulgare showed the highest MIC values (350-400 mg/L). Essential oils, especially those with BRC in their composition, presented inhibitory capacity against P. larvae strains

Nota corta. Evaluación de aceites esenciales de dos plantas silvestres y sus emulsificantes utilizados en tests de inhibición de Paenibacillus larvae subsp. Larvae

In honey bees (Apis mellifera L.), American foulbrood (AFB) is caused by the infection of the larvae and pupae with the bacterium Paenibacillus larvae subsp. larvae. The antibacterial effects of the essential oils of wild camomile (Tagetes minuta L.) and Andean thyme (Acantholippia seriphioides A. Gray) against different strains of P. larvae subsp. larvae were evaluated in vitro. The possible inhibitory effects of two emulsifiers of these oils (propylene glycol and soybean lecithin) were also assessed. Significant differences in antibacterial action were seen between the oils and emulsifiers (PLa patología conocida como loque americana, que afecta a los estadios de larva y pupa de abejas (Apis mellifera L.), es causada por la bacteria Paenibacillus larvae subsp. larvae. Se evaluó el efecto antibacteriano in vitro de los aceites esenciales de manzanilla silvestre (Tagetes minuta L.) y tomillo andino (Acantholippia seriphioides A. Gray) frente a diferentes cepas de P. larvae subsp. larvae, así como también el posible efecto inhibitorio adicional del propilenglicol y la lecitina de soja, utilizados como emulsionantes de los aceites esenciales. Los resultados de la evaluación in vitro indican diferencias significativas entre los dos aceites esenciales emulsionados (

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

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.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

Prediction of Cardiovascular Disease by the Framingham‐REGICOR Equation in the High‐Risk PREDIMED Cohort: Impact of the Mediterranean Diet Across Different Risk Strata

Background: The usefulness of cardiovascular disease (CVD) predictive equations in different populations is debatable. We assessed the efficacy of the Framingham‐REGICOR scale, validated for the Spanish population, to identify future CVD in participants, who were predefined as being at high‐risk in the PREvención con DIeta MEDiterránea (PREDIMED) study—a nutrition‐intervention primary prevention trial—and the impact of adherence to the Mediterranean diet on CVD across risk categories. Methods and Results: In a post hoc analysis, we assessed the CVD predictive value of baseline estimated risk in 5966 PREDIMED participants (aged 55–74 years, 57% women; 48% with type 2 diabetes mellitus). Major CVD events, the primary PREDIMED end point, were an aggregate of myocardial infarction, stroke, and cardiovascular death. Multivariate‐adjusted Cox regression was used to calculate hazard ratios for major CVD events and effect modification from the Mediterranean diet intervention across risk strata (low, moderate, high, very high). The Framingham‐REGICOR classification of PREDIMED participants was 25.1% low risk, 44.5% moderate risk, and 30.4% high or very high risk. During 6‐year follow‐up, 188 major CVD events occurred. Hazard ratios for major CVD events increased in parallel with estimated risk (2.68, 4.24, and 6.60 for moderate, high, and very high risk), particularly in men (7.60, 13.16, and 15.85, respectively, versus 2.16, 2.28, and 3.51, respectively, in women). Yet among those with low or moderate risk, 32.2% and 74.3% of major CVD events occurred in men and women, respectively. Mediterranean diet adherence was associated with CVD risk reduction regardless of risk strata (P>0.4 for interaction). Conclusions: Incident CVD increased in parallel with estimated risk in the PREDIMED cohort, but most events occurred in non–high‐risk categories, particularly in women. Until predictive tools are improved, promotion of the Mediterranean diet might be useful to reduce CVD independent of baseline risk