1. Inhibition of Paenibacillus larvae by different extracts and pure compounds from Flourensia spp.

MARÍA G. REYES, MARIELA J. TORRES, MATÍAS D. MAGGI, JUAN M. MARIOLI, ROBERTO R. GIL, VIRGINIA E. SOSA, MARÍA L. URIBURU, MARCELA E. AUDISIO

Industrial Crops and Products

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2013 vol. 50 p. 758 - 763

0926-6690

tPaenibacillus larvae, a sporulating Gram-positive bacterium, is the etiological agent of American foulbrooddisease in Apis mellifera L. Plant extracts could be a natural alternative to control this pathology. Thecurrent study assessed the anti-P. larvae effect of extracts and pure principal products from the Flourensiagenus: F. riparia, F. fiebrigii and F. tortuosa. Their inhibitory effect was assayed against different P. larvaestrains according to the disk diffusion technique and subsequently, the minimal inhibitory concentrations(MIC) of extracts by the agar dilution method was determined. Furthermore, toxicity of the most effectiveextracts against P. larvae was tested in bees. All extracts inhibited growth of the different P. larvae strainsassayed. However, the magnitude of the antagonistic effect depended on the chemical nature of theextract and the P. larvae strain. Chloroform extracts (CE) and ethyl ether extracts (ETE) from F. ripariaand ETE from F. fiebrigii were most active against P. larvae Azul, the most sensitive indicator strain withMIC values of 250 ppm (CE) and 2000 ppm (ETE) for F. riparia, and 2500 ppm (ETE) for F. fiebrigii. Hexaneextracts from the three species did not present any significant inhibitory effect. These results wouldindicate that one or some of the more polar compounds would cause inhibition of this pathogen. Toxicityassays demonstrated that even the highest concentrations assayed (125,000 ppm) did not show lethaleffects on exposed bees during in vitro conditions.Paenibacillus larvae, a sporulating Gram-positive bacterium, is the etiological agent of American foulbrooddisease in Apis mellifera L. Plant extracts could be a natural alternative to control this pathology. Thecurrent study assessed the anti-P. larvae effect of extracts and pure principal products from the Flourensiagenus: F. riparia, F. fiebrigii and F. tortuosa. Their inhibitory effect was assayed against different P. larvaestrains according to the disk diffusion technique and subsequently, the minimal inhibitory concentrations(MIC) of extracts by the agar dilution method was determined. Furthermore, toxicity of the most effectiveextracts against P. larvae was tested in bees. All extracts inhibited growth of the different P. larvae strainsassayed. However, the magnitude of the antagonistic effect depended on the chemical nature of theextract and the P. larvae strain. Chloroform extracts (CE) and ethyl ether extracts (ETE) from F. ripariaand ETE from F. fiebrigii were most active against P. larvae Azul, the most sensitive indicator strain withMIC values of 250 ppm (CE) and 2000 ppm (ETE) for F. riparia, and 2500 ppm (ETE) for F. fiebrigii. Hexaneextracts from the three species did not present any significant inhibitory effect. These results wouldindicate that one or some of the more polar compounds would cause inhibition of this pathogen. Toxicityassays demonstrated that even the highest concentrations assayed (125,000 ppm) did not show lethaleffects on exposed bees during in vitro conditions.