Efficacy of Essential Oils of Thymus vulgaris and Origanum vulgare on Echinococcus granulosus.

The aim of the present work was to determine the in vitro effect of T. vulgaris and O. vulgare essential oils against E. granulosus protoscoleces and cysts. Essential oils were added to the medium resulting in thymol final concentrations of 10 µg/mL. The essential oils had a time-dependent effect provoking the complete loss of protoscolex viability after 72 days of postincubation. The results were confirmed at the ultrastructure level. Loss of infectivity in protoscoleces incubated with O. vulgare after 60 days was observed. On the other hand, the weight of cysts recorded in mice inoculated with T. vulgaris treated protoscoleces was significantly lower than that obtained in control group. Gamma-glutamyl-transpeptidase activity was readily detected in the culture supernatant of protoscoleces treated either with the essential oils or thymol. T. vulgaris and O. vulgare essential oils and thymol can induce cell apoptosis of protoscoleces after short incubation times. The efficacy of T. vulgaris and O. vulgare essential oils was also demonstrated in vitro on E. granulosus murine cysts. Our data suggest that essential oils of T. vulgaris and O. vulgare have anthelmintic effect against protoscoleces and cysts of E. granulosus.

Evaluation of culture media for Paenibacillus larvae applied to studies of antimicrobial activity.

This study was conducted to compare different liquid culture media for Paenibacillus larvae growth in order to find the best one to be used in studies on activity of antimicrobial substances, such as essential oils. P. larvae presented poor growth in usual broths such as Mueller-Hinton, commonly employed in antimicrobial activity assays. Growth in liquid media was evaluated using Paenibacillus larvae strains isolated from hives located in different geographical zones. The MYT medium (Mueller-Hinton broth, yeast extract and thiamine) was selected out of the eight liquid media analyzed, as it proved to be the most adequate due to its higher absorbance at 620 nm. The following mean values were obtained from the four P. larvae strains: 0.227 +/- 0.016 for the Cobo strain, 0.279 +/- 0.015 for La Plata strain, 0.758 +/- 0.020 for Mechongué strain and 0.244 +/- 0.0079 for Sierra de los Padres strain, respectively.

Evaluation of culture media for Paenibacillus larvae applied to studies of antimicrobial activity / Evaluación de medios de cultivo para el crecimiento de Paenibacillus larvae aplicables en estudios de actividad antimicrobiana

This study was conducted to compare different liquid culture media for Paenibacillus larvae growth in order to find the best one to be used in studies on activity of antimicrobial substances, such as essential oils. P. larvae presented poor growth in usual broths such as Mueller-Hinton, commonly employed in antimicrobial activity assays. Growth in liquid media was evaluated using Paenibacillus larvae strains isolated from hives located in different geographical zones. The MYT medium (Mueller-Hinton broth, yeast extract and thiamine) was selected out of the eight liquid media analyzed, as it proved to be the most adequate due to its higher absorbance at 620 nm. The following mean values were obtained from the four P. larvae strains: 0.227 ± 0.016 for the Cobo strain, 0.279 ± 0.015 for La Plata strain, 0.758 ± 0.020 for Mechongué strain and 0.244 ± 0.0079 for Sierra de los Padres strain, respectively.

Este trabajo está orientado a comparar diferentes medios de cultivo líquidos para el crecimiento de Paenibacillus larvae. El objetivo fue encontrar el más apropiado para utilizar en estudios de actividad antimicrobiana de diferentes sustancias, tales como aceites esenciales. P. larvae presenta un crecimiento débil en medios de cultivo como el Mueller-Hinton, comúnmente usado en ensayos de actividad antimicrobiana. Se evaluó el crecimiento en caldos de cultivo de cepas aisladas de colmenas ubicadas en diferentes zonas geográficas. De los ocho medios analizados, el MYT (Mueller-Hinton, extracto de levadura y tiamina) mostró ser el más apropiado, en éste se observó el mayor valor de absorbancia a 620 nm. Los valores obtenidos en promedio para los cuatro aislamientos de P. larvae evaluados fueron 0,227 ± 0,016 (cepa de Cobo); 0,279 ± 0,015 (cepa de La Plata); 0,758 ± 0,020 (cepa de Mechongué) y 0,244 ± 0,0079 (cepa de Sierra de los Padres).

[Inhibition of Paenibacillus larvae employing a mixture of essential oils and thymol]. / Inhibición de Paenibacillus larvae empleando una mezcla de aceites esenciales y timol.

In vitro antimicrobial activity of a mixture of two essential oils and thymol against Paenibacillus larvae, causal agent of American Foulbrood (AFB), was evaluated. The essential oils were extracted from cinnamon (Cinnamomum zeylanicum) and thyme (Thymus vulgaris). The third component used, thymol, is the major component of the essential oil of thyme which contains 39.9% of thymol. Minimal inhibitory concentration (MIC) in Mueller-Hinton broth by the tube dilution method and minimal bactericide concentration (MBC) on MYPGP agar were evaluated. Thyme registered MIC values of 150-250 microg/ml and MBC values of 200-300 microg/ml, while the MIC and MBC values obtained for cinnamon were of 50-100 microg/ml and 100-125 microg/ml. Thymol showed similar MIC and MBC values of 100-150 microg/ml. No significant differences between the bacterial strains were detected, but significant differences between essential oils and thymol activity were registered (P<0,01). An inhibitory synergetic effect on AFB was observed reducing MIC and MBC values due to the use of a mixture of 62.5% of thyme, 12.5% of cinnamon and 25% of thymol.