Partial characterization of bacteriocin-like compounds from two strains of Bacillus cereus with biological activity against Paenibacillus larvae, the causal agent of American Foulbrood disease.

American Foulbrood (AFB), caused by the spore-forming Gram-positive bacterium Paenibacillus larvae, is the most severe bacterial disease affecting honeybees worldwide. Two bacterial isolates showing specific inhibitory activity against P. larvae were identified as Bacillus cereus by 16S rDNA sequencing. Antagonistic compounds were obtained from cell-free supernatants of strains m6c and m387 growing on Trypticase Soy Broth and concentrated by NH4 SO4 precipitation, ultrafiltration and butanol extraction. Both compounds were characterized as bacteriocin-like inhibitory substances (BLIS). BLISm6c and BLISm387 were stable at 70°C for 30 min and active in the pH range from 3 to 7. The antibacterial activity was completely lost at pH values higher than 8 or temperatures >80°C. Both BLIS have a narrow activity range and highly inhibit the growth of P. larvae. BLISm6c and BLISm387 differ from each other and other BLIS reportedly produced by B. cereus with regard to their molecular weights, antibacterial activity, minimal inhibitory concentration values and sensitivity to degradative enzymes. The findings of this study suggest that BLISm6c and BLISm387 can potentially be used to control AFB. SIGNIFICANT AND IMPACT OF THE STUDY: An Integrated Pest Management (IPM) approach is needed to ensure the sustainability of the beekeeping industry due to the increasing demand for organic honey and the reduction of dependence on antibiotics. Biocontrol agents produced by bacteria isolated from apiarian sources seem promising and able to combine with an IPM strategy. The most significant findings of this study are the characterization of bacteriocin-like compounds (BLIS) obtained from two strains of Bacillus cereus isolated from honey. Both BLIS have a narrow activity range and highly inhibit the growth of Paenibacillus larvae, the causal agent of American Foulbrood disease of honey bees.

Purificación parcial y caracterización de una sustancia antimicrobiana producida por Alteromonas sp. de origen marino

Un miembro del género Alteromonas sp. (cepa N22.C), aislado del neuston marino y productor de sustancias que inhiben el crecimiento de ictiopatógenos fue caracterizado fenotípicamente mediante pruebas morfológicas, fisiológicas y bioquímicas convencionales. Para determinar la naturaleza química de la sustancia inhibitoria, extractos crudos de sobrenadantes de cultivos fueron precipitados con concentraciones crecientes de Sulfato de Amonio hasta el 70% y filtrados a través de columnas de Sephadex G-25. Ensayos con Dodecil Sulfato de Sodio-electroforesis en Geles de Poliacrilamida (SDSPAGE) revelaron que la sustancia antimicrobiana es un compuesto proteináceo con una masa molecular de aproximadamente 34000 Da, que carece de residuos de azúcares asociados. Otros ensayos realizados con extractos crudos y fracciones semipurificadas de la cepa de Alteromonas sp. N22.C mostraron un amplio espectro de actividad antibiótica contra cepas de bacterias patógenas de peces, moluscos y crustáceos.

A member of the genus Alteromonas sp. (strain N22.C) isolated from marine neuston and substance-producer which inhibit growth of ichthyopathogenics was characterized phenotipically by means of morphological, physiological and biochemical conventional tests. To determine the chemical nature of the inhibitory substance, raw extracts of supernatans from cultured strains were precipitated with increasing concentrations of Ammonium Sulphate up to 70% and filtered through columns of Sephadex G-25. Assays by Sodium Dodecyl SulfatePolyacrylamide Gel Electrophoresis (SDSPAGE) revealed that the antimicrobial substance is a proteinaceous compound with a molecular mass of approximately 34000 Da, which lacks sugar associated residues of it. Other assays made with raw semipurified fractions extracts of Alteromonas sp N22.C show the wide spectrum of antibiotic activity against pathogenic bacterial strains of fish, mollusks and crustaceans.

Inibidores microbianos em leite pasteurizado do comércio da cidade de São Paulo / Microbe inhibitors in pasteurized milk sold in Säo Paulo city, Brazil

Foram analisadas 404 amostras de leite pasteurizado, tipos B e Especial no período 1981-1982. Destas, 172 (42,57%) foram positivas para antibióticos e/ou anti-sêpticos, como segue: (3,96%) para antibióticos pelo método de difusão em disco e 47 (11,63%) pelo Delvo-teste; 19 (4,70%) para antibióticos e anti-sépticos e 90 (22,28%) para anti-sépticos. Houve redução no teor de antibióticos nas amostras de 1982, em relação às de 1981, considerando a sensibilidade dos microrganismos usados para a sua detecção. Dentre os vários microrganismos usados para a detecçâo de arrti-sépticos, os bacilos gram-ncgativos foram inibidos com maior f reqüêncía, seguidos dos bacilos e cocos gram-posi tivos. Há, pelos resultados, indicação da utilização de an ti-sêpticos diversos. Não houve redução da presença desta classe de inibidores durante o período de observação assinalado. Em 73 amostras, realizou-se também o exame bacteriológico. Destas, 21 apresentaram-se de acordo com os padrões legais estabelecidos e livres de substâncias inibidoras. Entre as demais, 28 amostras estavam em desacordo com os padrões microbiológicos, porém livres de inibidores; 5 amostras acusavam a presença de antibióticos e 14, a de anti-sépticos; 5 destas amostras estavam de acordo com os padrões microbiológicos, porém 4 delas continham antibióticos e uma, anti-sêptico (AU).