Resumen Aleaciones cristalinas desordenadas Fe50Mn25+xSn25_x, con x = -1.25, 0.0, 2.5, 5.0, 7.5, cercanas a las composiciones de Heusler-211, fueron preparadas por fusión en atmósfera inerte, subsecuentemente, sometidas a recocido térmico durante 4 días a 1173 K y, finalmente, enfriadas en agua helada. Todas las aleaciones han sido sistemáticamente analizadas mediante difracción de rayos X, espectroscopias Mössbauer de 57Fe y 119Sn, y medidas de magnetización a temperatura ambiente. Los análisis Rietveld de los difractogramas de las muestras con x = -1.25 y 0.0 muestran la presencia de dos fases cristalográficas hexagonales: (i) la solución solida químicamente desordenada ε-(Fe/Mn)3Sn (mayoritaria), y (ii) el intermetálico ε-Fe5Sn3 (minoritaria); mientras que, las aleaciones con x = 2.5, 5.0 y 7.5, presentan solo la solución sólida desordenada, ε-(Fe/Mn)3(Sn/Fe/Mn). Si bien, las composiciones de las aleaciones Fe50Mn25+xSn25-x son cercanas a las de Heusler-211, ninguna tiene la estructura cúbica L2 1 característica de estas. Los tamaños medios de los cristalitos, calculados por el método de Williamson-Hall, están dentro del rango 62-256 nm y disminuyen cuando x aumenta. Los resultados Mössbauer de todas las aleaciones muestran la característica de magnetismo localizado a través de la distribución de campos magnéticos hiperfinos en los sitios de Fe, y de magnetismo itinerante a través de los campos transferidos desde los átomos de Fe en los núcleos de 119Sn. Los campos coercitivos y remanentes, obtenidos por medidas de magnetización bajo campo magnético aplicado entre -2200 y +2200 Oe, disminuyen cuando x aumenta. Los valores de los campos coercitivos están en el rango de los magnetos blandos (1-20 Oe).

Abstract Disordered crystalline Fe50Mn25+xSn25-x alloys, with x = -1.25, 0.0, 2.5, 5.0, 7.5 (close to the full-Heusler alloys), were arc-melted in a high purity argon atmosphere and the molten pellets were individually sealed in quartz tubes also under argon atmosphere. Subsequently, they were annealed at 1173 K for 4 days, being finally quenched in a bath with cold water. Structural and magnetic properties have systematically been studied using X-ray diffraction, 57Fe, and 119Sn Mössbauer spectroscopies, and magnetization measurements recorded at room temperature. Rietveld refinement of the X-ray diffraction patterns of the annealed samples with x = -1.25 and 0 has revealed the presence of two hexagonal crystallographic phases: (i) a chemically disordered solid solution identified as ε-(Fe/Mn)3Sn (majority fraction) and (ii) the ε-Fe5Sn3 intermetallic compound (minority fraction). For samples with x = 2.5, 5.0, and 7.5, the Rietveld analysis has only indicated the presence of a chemically disordered solid solution identified as ε -(Fe/Mn)3(Sn/Fe/Mn). Although compositions of the Fe50Mn25+xSn25_x alloys are close to that of full-Heusler alloys, none of them has the expected L2 1 structure. The average crystallite sizes, estimated from the Williamson-Hall method, are in the range of 256-62 nm. The average sizes has gradually decreased as the x-content is increased. Mössbauer results have shown localized-type magnetism from Fe non-equivalent sites, and itinerant-like magnetism on 119Sn-probes. Magnetic hysteresis loops, recorded at 300 K for a maximum field of 2200 Oe, have indicated that the remanent and coercive fields have systematically decreased as the x-parameter has increased. Coercive fields are in the range for soft magnets (1-20 Oe).

ABSTRACT Objectives: To evaluate the in vitro photodynamic activity of aluminum phthalocyanine tetrasulfonate chloride (AlPcClS4) on promastigotes and amastigotes of Leishmania (Viannia) peruviana and Leishmania (Viannia) braziliensis. Materials and methods: The activity of photodynamic therapy using AlPcClS4 on Leishmania promastigote and amastigotes was determined by the Methyl Thiazole Tetrazolium (MTT) colorimetric method and quantitative PCR, respectively. Results: Photodynamic treatment showed an inhibitory effect on promastigotes, particularly on Leishmania (V.) peruviana, to a lesser extent on Leishmania (V.) braziliensis and also on intracellular forms of both species. At 24 hours post-radiation, using concentrations of 200 μM and 350 μM, the inhibitory effect on Leishmania (V.) peruviana was 72.9% and 73.9% respectively; at 96 hours the inhibitory effect was of 78.8% and 80.6%, respectively. Regarding intracellular forms, the inhibitory effect on Leishmania (V.) peruviana amastigotes was 57.8% at 72 hours post-treatment, using a concentration of 200 μM. The IC50 was 56.5, 50, 44 and 39.7 μM, at 24, 48, 72 and 96 hours post-radiation, respectively. Conclusions: Photodynamic therapy using AlPcClS4 against Leishmania species showed encouraging results, mainly on Leishmania (V.) peruviana, suggesting a potential use as an alternative or complement to the usual treatment of tegumentary leishmaniasis. However, new trials are still required to determine the selectivity index for the intracellular form of the parasite, and to develop methods to facilitate the efficient entry of the molecule into the host cell and the parasite.

RESUMEN Objetivos: Evaluar la actividad fotodinámica in vitro de la ftalocianina de aluminio tetrasulfonada clorada (AlPcClS4) sobre promastigotes y amastigotes de Leishmania (Viannia) peruviana y Leishmania (Viannia) braziliensis. Materiales y métodos: La actividad del tratamiento fotodinámico empleando AlPcClS4 sobre promastigotes y amastigotes de Leishmania fue determinada mediante el método colorimétrico Metil Tiazol Tetrazolium (MTT) y PCR cuantitativo, respectivamente. Resultados: El tratamiento fotodinámico presentó un efecto inhibitorio sobre promastigotes, principalmente sobre Leishmania (V.) peruviana, en menor proporción sobre Leishmania (V.) braziliensis y sobre las formas intracelulares de ambas especies. En Leishmania (V.) peruviana, a las 24 horas posirradiación a 200 µM y 350 µM el efecto inhibitorio fue del 72,9% y 73,9%, respectivamente y a las 96 horas fue del 78,8% y 80,6%, respectivamente. En las formas intracelulares, empleando 200 µM y evaluado a las 72 horas postratamiento, se observó una inhibición del 57,8% de amastigotes de Leishmania (V.) peruviana. El IC50 fue del 56,5; 50; 44; y 39,7 µM, que corresponde a las 24, 48, 72 y 96 horas posirradiación, respectivamente. Conclusiones: El tratamiento fotodinámico empleando AlPcClS4 frente a las especies de Leishmania presentó resultados alentadores principalmente sobre Leishmania (V.) peruviana, lo cual sugiere su potencial uso como alternativa o complemento del tratamiento convencional de la leishmaniasis tegumentaria. Sin embargo, aún se requiere continuar con nuevos ensayos para determinar el índice de selectividad sobre el parásito en su forma intracelular, y desarrollar estrategias que faciliten el ingreso eficiente de la molécula hacia la célula hospedera y al parásito.

Abstract As part of the rhizosphere microbiota, actinomycetes interact with their host by releasing metabolites that positively influence their host’ growth. The main objective of this study was to evaluate the plant growth-promoting capacity of actinomycetes isolated from the rhizosphere of potato crops collected in the city of San Jeronimo, Andahuaylas, Peru. Forty-nine actinomycetes strains were isolated and screened for their capacity to solubilize phosphates, fix atmospheric nitrogen, produce indole acetic acid (IAA) and produce siderophores. Out of the total number of isolates, 33 (63.27%) solubilized phosphates, 42 (87.72%) fixed atmospheric nitrogen, 10 (20.41%) produced IAA and 18 (24.49%) were siderophore producers; strains AND 13 and AND 16 being the top performers. AND 13 was identified by 16S RNAr gene amplification as Streptomyces sp. The results indicate that actinomycetes can be considered as potential PGPR organisms and could be included in biofertilization programs of potato crops as an alternative to agrochemicals.

ABSTRACT Objectives: To evaluate the in vitro photodynamic activity of aluminum phthalocyanine tetrasulfonate chloride (AlPcClS4) on promastigotes and amastigotes of Leishmania (Viannia) peruviana and Leishmania (Viannia) braziliensis. Materials and methods: The activity of photodynamic therapy using AlPcClS4 on Leishmania promastigote and amastigotes was determined by the Methyl Thiazole Tetrazolium (MTT) colorimetric method and quantitative PCR, respectively. Results: Photodynamic treatment showed an inhibitory effect on promastigotes, particularly on Leishmania (V.) peruviana, to a lesser extent on Leishmania (V.) braziliensis and also on intracellular forms of both species. At 24 hours post-radiation, using concentrations of 200 μM and 350 μM, the inhibitory effect on Leishmania (V.) peruviana was 72.9% and 73.9% respectively; at 96 hours the inhibitory effect was of 78.8% and 80.6%, respectively. Regarding intracellular forms, the inhibitory effect on Leishmania (V.) peruviana amastigotes was 57.8% at 72 hours post-treatment, using a concentration of 200 μM. The IC50 was 56.5, 50, 44 and 39.7 μM, at 24, 48, 72 and 96 hours post-radiation, respectively. Conclusions: Photodynamic therapy using AlPcClS4 against Leishmania species showed encouraging results, mainly on Leishmania (V.) peruviana, suggesting a potential use as an alternative or complement to the usual treatment of tegumentary leishmaniasis. However, new trials are still required to determine the selectivity index for the intracellular form of the parasite, and to develop methods to facilitate the efficient entry of the molecule into the host cell and the parasite.

RESUMEN Objetivos: Evaluar la actividad fotodinámica in vitro de la ftalocianina de aluminio tetrasulfonada clorada (AlPcClS4) sobre promastigotes y amastigotes de Leishmania (Viannia) peruviana y Leishmania (Viannia) braziliensis. Materiales y métodos: La actividad del tratamiento fotodinámico empleando AlPcClS4 sobre promastigotes y amastigotes de Leishmania fue determinada mediante el método colorimétrico Metil Tiazol Tetrazolium (MTT) y PCR cuantitativo, respectivamente. Resultados: El tratamiento fotodinámico presentó un efecto inhibitorio sobre promastigotes, principalmente sobre Leishmania (V.) peruviana, en menor proporción sobre Leishmania (V.) braziliensis y sobre las formas intracelulares de ambas especies. En Leishmania (V.) peruviana, a las 24 horas posirradiación a 200 µM y 350 µM el efecto inhibitorio fue del 72,9% y 73,9%, respectivamente y a las 96 horas fue del 78,8% y 80,6%, respectivamente. En las formas intracelulares, empleando 200 µM y evaluado a las 72 horas postratamiento, se observó una inhibición del 57,8% de amastigotes de Leishmania (V.) peruviana. El IC50 fue del 56,5; 50; 44; y 39,7 µM, que corresponde a las 24, 48, 72 y 96 horas posirradiación, respectivamente. Conclusiones: El tratamiento fotodinámico empleando AlPcClS4 frente a las especies de Leishmania presentó resultados alentadores principalmente sobre Leishmania (V.) peruviana, lo cual sugiere su potencial uso como alternativa o complemento del tratamiento convencional de la leishmaniasis tegumentaria. Sin embargo, aún se requiere continuar con nuevos ensayos para determinar el índice de selectividad sobre el parásito en su forma intracelular, y desarrollar estrategias que faciliten el ingreso eficiente de la molécula hacia la célula hospedera y al parásito.

Abstract Potato (Solanum tuberosum L.) is the fourth most consumed food crop in the world, whose production in Peru is diminished due to phytosanitary problems and high costs of chemical fertilizers. In the present work, 32 actinomycetes isolated from the rhizosphere of organic native potato crops collected in the town of Cabana, Lucanas, Ayacucho, were characterized phenotypically and evaluated for their in vitro antagonistic capacity against Oomycete phytopathogen Phytophthora infestans. The characterization tests showed that 97% of the actinomycetes were able to assimilate glucose, sucrose, and mannitol; as well as producing extracellular enzymes like amylases (100%) and cellulases (50%). Furthermore, the growth in laboratory culture was better in the range of pH 5.5-8.5 and temperature 28-30 °C. From the tests of antagonism in oat agar (71.9%) and rye agar (31.2%), three strains were selected according to the native potato variety were selected as CAB10-J2 (Ccompis), CAB9-CA4 (Cuchipa-akan) and CAB5-F5 (Futis) with pathogen inhibition rates of 80.05, 77.47 and 37.5% respectively. The strains were identified by molecular tests as members of the genus Streptomyces and owners of polyketide synthase (PKS) genes. It is concluded that the rhizospheric actinomycetes of potato are producers of bioactive compounds capable of remarkably inhibiting the pathogen Phytophthora infestans, being able to be considered candidates in biological control programs of the "potato blight".

Potato crops are affected by a great number of pathogens that decrease their quality and productivity. One way of controlling these phytopathogens is through the use of antagonistic microorganisms, especially those isolated from the microbial community located in the rhizosphere. In this study, 49 strains of actinomycetes were isolated and their antagonist capacity against phytopathogens that affect Solanum tuberosum was assessed. 26.5% showed antagonist activity against Pectobacterium carotovorum, 69.4% against Fusarium sp., 44.9% against Lasiodiplodia sp., 55.1% against Rhizoctonia solani and 46.9% against Phytophthora infestans. Cultures of two selected actinomycetes (AND 12 and AND 24) were treated with ethyl acetate, dichloromethane, hexane and butanol, whose crude extracts showed antimicrobial activity, being the most important the extract obtained with ethyl acetate due to its greater spectrum of inhibitory activity. The selected strains were identified by phylogenetic analysis of the 16S rRNA gene as members of the genus Streptomyces. Due to their antagonist capacity demonstrated in the present study, rhizospheric actinomycetes could be considered as potential candidates to be used in pathogen control programs that affect potatoes.

El cultivo de la papa se ve afectado por una gran cantidad de patógenos que disminuyen su calidad y productividad. Uno de los métodos de control de estos fitopatógenos es mediante el uso de microorganismos antagonistas, en especial aquellos que se aíslan de la comunidad microbiana presente en la rizósfera. En este trabajo, se aislaron 49 cepas de actinomicetos y se evaluaron sus capacidades antagonistas frente a fitopatógenos que afectan a Solanum tuberosum. El 26.5% presentó capacidad antagónica frente a Pectobacterium carotovorum, el 69.4% a Fusarium sp., el 44.9% a Lasiodiplodia sp., el 55.1% a Rhizoctonia solani y el 46.9% a Phytophthora infestans. Cultivos de dos actinomicetos seleccionados (AND 12 y AND 24) fueron tratados con acetato de etilo, diclorometano, hexano y butanol, cuyos extractos crudos mostraron actividad antimicrobiana, siendo el extracto obtenido con acetato de etilo el más importante por presentar mayor espectro de actividad inhibitoria. Las cepas seleccionadas se identificaron por análisis filogenético del gen del ARNr 16S como miembros del género Streptomyces. Los actinomicetos rizosféricos, por su probada capacidad antagonista demostrada en el presente estudio, podrían ser considerados como potenciales candidatos a ser utilizados en programas de control de patógenos que afectan a la papa.

ABSTRACT Objectives. To isolate, select and identify actinomyces associated to leaf-cutting ants Atta cephalotes (Linnaeus, 1758), that present a greater anti-Candida activity. Materials and Methods. Cross-sectional study made with ants collected at a location in Huánuco, Peru, from which strands of actinomyces were isolated and later evaluated by in vitro testing in order to determine its antagonistic capacity against species of Candida. The actinomyces with greater antagonism were selected and cultured by agitation, then the reliable extracellular metabolites were obtained with organic solvents, and finally the crude extracts were evaluated to determine quantitatively the minimum inhibiting concentration (MIC). Results. Thirty (30) actinomyces were isolated, of which 47% exhibited antagonistic activity against Candida albicans (C. albicans) ATCC 7516, 43% to Candida parapsilosis ATCC 7307, 37% to Candida tropicalis ATCC 7206 and C. albicans ATCC 10231, and 30% to C. albicans ATCC 98028. Organic extracts of the HAA-16 and HAA-17 strands exhibited noticeable anti-Candida activity, being the ethyl acetate extract of the HAA-17 strand the one with the highest performance thanks to a wider activity spectrum of MIC 3.25 mg/mL against C. albicans ATCC 7516 and Candida parapsilosis ATCC 7307. The selected actinomyces were identified by means of molecular techniques as members of the Streptomyces genus. Conclusions. Actinomyces associated to Atta cephalotes are excellent producers of bioactive compounds, being able to inhibit the growth of pathogenic mold of the Candida genus and with potential for application in the development of new natural products for the biomedical field.

RESUMEN Objetivos. Aislar, seleccionar e identificar actinomicetos asociados a hormigas cortadoras de hojas Atta cephalotes (Linnaeus, 1758), que presenten mayor actividad anti-Candida. Materiales y métodos. Estudio transversal realizado en hormigas recolectadas de una localidad de Huánuco, Perú, a partir de las cuales se aislaron cepas de actinomicetos que fueron evaluadas mediante pruebas in vitro para determinar su capacidad antagonista frente a especies de Candida. Los actinomicetos de mayor antagonismo fueron seleccionados y cultivados en agitación, luego se obtuvieron los metabolitos extracelulares con solventes orgánicos y finalmente se evaluaron los extractos crudos para determinar cuantitativamente la concentración mínima inhibitoria (CMI). Resultados. Se logró aislar 30 actinomicetos, de los cuales el 47 % presentaron actividad antagonista a Candida albicans (C. albicans) ATCC 7516, el 43 % a Candida parapsilosis ATCC 7307, el 37% a Candida tropicalis ATCC 7206 y C. albicans ATCC 10231 y el 30% a C. albicans ATCC 98028. Extractos orgánicos de las cepas HAA-16 y HAA-17 presentaron marcada actividad anti-Candida; siendo el extracto de acetato de etilo de la cepa HAA17 el de mejor rendimiento por tener mayor espectro de actividad y presentar una CMI de 3,25 mg/ml frente a C. albicans ATCC 7516 y Candida parapsilosis ATCC 7307. Los actinomicetos seleccionados se identificaron mediante técnicas moleculares como miembros del género Streptomyces. Conclusiones. Los actinomicetos asociados a Atta cephalotes son excelentes productores de compuestos bioactivos, capaces de inhibir el crecimiento de levaduras patógenas del género Candida y con potencial aplicación en el desarrollo de nuevos productos naturales de interés biomédico.

Objectives. To isolate, select and identify actinomyces associated to leaf-cutting ants Atta cephalotes (Linnaeus, 1758), that present a greater anti-Candida activity. Materials and Methods. Cross-sectional study made with ants collected at a location in Huánuco, Peru, from which strands of actinomyces were isolated and later evaluated by in vitro testing in order to determine its antagonistic capacity against species of Candida. The actinomyces with greater antagonism were selected and cultured by agitation, then the reliable extracellular metabolites were obtained with organic solvents, and finally the crude extracts were evaluated to determine quantitatively the minimum inhibiting concentration (MIC). Results. Thirty (30) actinomyces were isolated, of which 47% exhibited antagonistic activity against Candida albicans (C. albicans) ATCC 7516, 43% to Candida parapsilosis ATCC 7307, 37% to Candida tropicalis ATCC 7206 and C. albicans ATCC 10231, and 30% to C. albicans ATCC 98028. Organic extracts of the HAA-16 and HAA-17 strands exhibited noticeable anti-Candida activity, being the ethyl acetate extract of the HAA-17 strand the one with the highest performance thanks to a wider activity spectrum of MIC 3.25 mg/mL against C. albicans ATCC 7516 and Candida parapsilosis ATCC 7307. The selected actinomyces were identified by means of molecular techniques as members of the Streptomyces genus. Conclusions. Actinomyces associated to Atta cephalotes are excellent producers of bioactive compounds, being able to inhibit the growth of pathogenic mold of the Candida genus and with potential for application in the development of new natural products for the biomedical field.

Objetivos. Aislar, seleccionar e identificar actinomicetos asociados a hormigas cortadoras de hojas Atta cephalotes (Linnaeus, 1758), que presenten mayor actividad anti-Candida. Materiales y métodos. Estudio transversal realizado en hormigas recolectadas de una localidad de Huánuco, Perú, a partir de las cuales se aislaron cepas de actinomicetos que fueron evaluadas mediante pruebas in vitro para determinar su capacidad antagonista frente a especies de Candida. Los actinomicetos de mayor antagonismo fueron seleccionados y cultivados en agitación, luego se obtuvieron los metabolitos extracelulares con solventes orgánicos y finalmente se evaluaron los extractos crudos para determinar cuantitativamente la concentración mínima inhibitoria (CMI). Resultados. Se logró aislar 30 actinomicetos, de los cuales el 47 % presentaron actividad antagonista a Candida albicans (C. albicans) ATCC 7516, el 43 % a Candida parapsilosis ATCC 7307, el 37% a Candida tropicalis ATCC 7206 y C. albicans ATCC 10231 y el 30% a C. albicans ATCC 98028. Extractos orgánicos de las cepas HAA-16 y HAA-17 presentaron marcada actividad anti-Candida; siendo el extracto de acetato de etilo de la cepa HAA-17 el de mejor rendimiento por tener mayor espectro de actividad y presentar una CMI de 3,25 mg/ml frente a C. albicans ATCC 7516 y Candida parapsilosis ATCC 7307. Los actinomicetos seleccionados se identificaron mediante técnicas moleculares como miembros del género Streptomyces. Conclusiones. Los actinomicetos asociados a Atta cephalotes son excelentes productores de compuestos bioactivos, capaces de inhibir el crecimiento de levaduras patógenas del género Candida y con potencial aplicación en el desarrollo de nuevos productos naturales de interés biomédico.

The presence of Plesiomonas shigelloides causing enteric disease in tilapia Oreochromis niloticus in a fish farm in Lima region, Peru is reported. The bacteria were isolated and identified as Plesiomonas shigelloides by conventional biochemical techniques and confirmed by theAPI 20NE system (numerical profile 7162744 that ratifies 99.3% P. shigelloides). Strains evaluated (n=4) had a fermentative metabolism of glucose, test positive to cytochrome oxidase, indole, Voges-Proskauer and methyl red. The most frequent external signs were erythema in abdomen and pectoral fins, and prominent and reddened anus with bloody discharge. Internally, ascites in visceral cavity and gut inflammation were detected. Histopathology studies revealed edema of the lamina propia and epithelial necrosis of gastric and intestinal tissue, and necrosis in anterior kidney and gonad

En el presente trabajo se reporta la presencia de Plesiomonas shigelloides causando un cuadro patológico entérico en tilapia Oreochromis niloticus en una piscigranja de la región Lima, Perú. Las bacterias fueron aisladas e identificadas por técnicas bioquímicas convencionales y confirmadas por el sistema API 20NE (perfil numérico 7162744 que ratifica a P. shigelloides al 99.3%). Las cepas evaluadas (n=4) presentaron un metabolismo fermentativo de glucosa, positividad en las pruebas de citocromo oxidasa, indol, Voges-Proskauer y rojo de metilo. Los signos externos más frecuentes de la enfermedad fueron eritema en el vientre y las aletas pectorales, ano prominente y enrojecido con descarga sanguinolenta. Internamente se observó el intestino inflamado y la presencia de líquido ascítico en la cavidad visceral. El estudio histopatológico reveló edema de la lámina propia y necrosis epitelial del tejido gástrico e intestinal, y necrosis en el riñón anterior y gónadas

Los metabolitos de un actinomiceto de origen marino, identificado como Streptomyces erythrogriseus cepa M10-77, fueron evaluados por su capacidad antimicrobiana y sinérgica con antibióticos convencionales. Las pruebas de antagonismo se realizaron frente a patógenos multidrogorresistentes (MDR) de origen clínico, siendo muy efectivos principalmente frente a especies patógenas de Staphylococcus y Enterococcus. Se determinó la Concentración Mínima Inhibitoria (CMI) de extractos diclorometánicos frente a los patógenos S. aureus 1094, S. epidermidis 1093 y Staphylococcus coagulasa negativo 348, siendo estos valores de 3,9; 15,7 y 1,9 µg/mL respectivamente. Los componentes del extracto diclorometánico fueron fraccionados parcialmente, obteniéndose hasta 4 fracciones orgánicas (I, II, III, IV), las que mostraron actividades inhibitorias de la cepa referencial S. aureus ATCC 43300. Los bioensayos frente a S. aureus meticilino resistente (MRSA) mostraron actividad sinérgica de la fracción II del extracto con antibióticos betalactámicos y aminoglucósidos, resaltando la repotenciación de la actividad de la bencilpenicilina en 128 veces el valor basal; así como de la gentamicina en 8 veces sobre el valor basal. S. erythrogriseus cepa M10-77 resultó ser un productor de metabolitos antibacterianos de alta potencia y con actividad sinérgica con antibióticos de referencia médica.

Metabolites of a marine actinomycete, identified as Streptomyces erythrogriseus M10-77 strain were evaluated for antimicrobial and synergistic activity with conventional antibiotics. Antagonism tests were conducted against multidrug resistant (MDR) pathogens of clinical origin, being very effective mainly against pathogenic Staphylococcus and Enterococcus. Minimum Inhibitory Concentrations (MIC) of dichloromethane extracts were determined against pathogenic S. aureus 1094, S. epidermidis and coagulase-negative Staphylococcus 1093 348, these values being 3.9; 15.7 and 1.9 μg/mL respectively. The components of dichloromethane extracts were fractionated partially yielding four organic fractions (I, II, III, IV), which showed inhibitory activity against the reference strain S. aureus ATCC 43300. The bioassays against S.aureus methicillin-resistant (MRSA ) produced synergistic activity of the extract fraction II with beta-lactams and aminoglycoside antibiotics, highlighting the upgrading of the activity of penicillin at 128 times above the baseline and gentamicin 8-fold above baseline. S. erythrogriseus M10-77 strain proved to be a producer of antibacterial metabolites with high power and synergistic activity with antibiotics of medical use.

One way of controlling phytopathogens is through the use antagonistic microorganisms. Compost is a source of microorganisms capable of producing secondary metabolites of agricultural interest. We isolated 85 actinomycetes in vitrocultures and evaluated their antagonist capacity against phytopathogens affecting Solanum tuberosum. Of the isolates, 23.5 % showed antagonistic activity against Ralstonia solanacearum, 16.4 % against Pectobacterium carotovorum, 43.5 % against Phytophthora infestans, 25.8 % against Fusarium sp., and 61.1% against Rhizoctonia solani. Organic extracts obtained from the selected strains (AACI-5, ACZI-22, ACZII-35, ACZIII-84 y ACZIII-88) with ethyl acetate and dichloromethane showed antimicrobial activity. The most important was the ethyl acetate extract from the AACI-5 strain, which had a broader spectrum of activity and showed a minimum inhibitory concentration (MIC) against Phytophthora infestans of 0.0625 mg.mL-1. The most active strains were identified as members of the genus Streptomyces. Due to the antagonist capacity showed by actinomycetes in this work, they could be considered as potential candidates for controlling potato pathogens under the framework of sustainable agriculture.

Una de las formas de control de fitopatógenos es a través del uso de microorganismos antagonistas. El compost, un producto orgánico es fuente de microorganismos capaces de producir metabolitos secundarios de interés agrícola. Se aislaron y evaluaron mediante cultivos in vitro la capacidad antagonista de 85 actinomicetos frente a fitopatógenos que afectan a Solanum tuberosum. De los aislados, 23.5% tuvieron actividad antagonista a Ralstonia solanacearum, 16.4% a Pectobacterium carotovorum, 43.5% a Phytophthora infestans, 25.8% a Fusarium sp y 61.1% a Rhizoctonia solani. Extractos orgánicos obtenidos con acetato de etilo y diclorometano de las cepas seleccionadas (AACI-5, ACZI-22, ACZII-35, ACZIII-84 y ACZIII-88) mostraron actividad antimicrobiana, siendo el de mayor importancia el extracto de acetato de etilo de la cepa AACI-5 por tener mayor espectro de actividad y presentar una Concentración Mínima Inhibitoria (CMI) de 0.0625 mg.mL-1 frente a Phytophthora infestans. Las cepas con mayor actividad se identificaron como miembros del género Streptomyces. Los actinomicetos por su capacidad antagonista mostrada en el presente trabajo podrían ser considerados potenciales candidatos en el control de patógenos de este tubérculo en el marco de una agricultura sostenible.

This study evaluated the presence of bacterial and micotic agents in 120 paiches (Arapaima gigas) in two fish farms in the Peruvian Amazon. Findings included seven bacterial agents: Pseudomonas spp, Bacillus spp, Staphylococcus spp,Streptococcus spp, Escherichia spp, Aeromonas hydrophila and Corynebacterium spp, and one fungus: Saprolegnia spp

Seevaluóla presenciadeagentesbacterianos ymicóticosen 120 paiches(Arapaima gigas) de dos centros de cultivo de la Amazonía peruana. Se reporta la presencia de siete agentes bacterianos: Pseudomonas spp, Bacillus spp, Staphylococcus spp, Streptococcus spp, Escherichia spp, Aeromonas hydrophila y Corynebacterium spp, y de un hongo: Saprolegnia spp

No presente trabalho foram estudadas 74 bactérias lácticas para determinar sua capacidade de inibir o desenvolvimento de Listeria monocytogenes ATCC 7644 ou L. innocua ATCC 33090. Dentro das 7 que exibiram atividade, 2 foram selecionadas para estudos complementares e se identificaram por métodos fenotípicos e genotípicos como Enterococcus mundtii Tw 56 e Lactococcus lactis subsp. lactis Tw 34. Depois da neutralização com NaOH e tratamento térmico (100 ºC e 121 ºC durante 5 min) a atividade antagonista do sobrenadante livre de células se manteve ativa. O tratamento com lisozima, lipase e catalase não afetou a atividade antimicrobiana. Entretanto, a atividade enzimática da tripsina suprimiu a ação inibidora do sobrenadante, confirmando a natureza proteica do composto ativo. Em ambos os casos, o título da atividade antilisteria não se viu afetado depois da indução mediada por nisina ou galactose. A combinação dos sobrenadantes livres de células não exibiu antagonismo ou sinergia. As características bioquímicas e fisioquimicas dos agentes antilisteria produzidos pelas cepas selecionadas sugerem que podem ser classificadas como bacteriocinas tipo I ou II. Devem ser realizados estudos complementares para determinar o uso potencial das cepas selecionadas como culturas bioprotetoras no controle da segurança alimentar.

In the present work, 74 strains of lactic bacteria isolated from the marine environment were studied in order to determinate their ability to inhibit the growth of Listeria monocytogenes ATCC 7644 or L. innocua ATCC 33090. Among the 7 strains that exhibited some activity, 2 were selected for further studies and identified by phenotypic and genotypic methods as Enterococcus mundtii Tw 56 y Lactococcus lactis subsp. lactis Tw 34. After neutralization with NaOH and heat treatment (100 ºC and 121 ºC for 5 min) the antagonistic activity of cell-free supernatants of the two strains studied remained active. Treatment with lysozime, lipase and catalase did not affect the antimicrobial activity; however enzymatic activity of trypsin abolished the inhibitory action of the supernatant, confirming the proteinacious nature of the active compound. In both cases, the titre of antilisterial activity was not affected after nisin or galactose-mediated induction. The combination of cell-free supernatants of both strains did not display antagonism or synergy. The biochemical and physicochemical characteristics of antilisterial agents produced by the selected strains suggest that they can be classified as type I or II bacteriocins. Further studies will be adressed to determine the potential use of the selected strains as bioprotective cultures in food safety control.

En el presente trabajo se estudiaron 74 bacterias lácticas para determinar su capacidad de inhibir el desarrollo de Listeria monocytogenes ATCC 7644 o L. innocua ATCC 33090. Dentro de las 7 que exhibieron actividad, 2 se seleccionaron para estudios complementarios y se identificaron por métodos fenotípicos y genotípicos como Enterococcus mundtii Tw 56 y Lactococcus lactis subsp. lactis Tw 34. Después de la neutralización con NaOH y tratamiento térmico (100 ºC y 121 ºC durante 5 min) la actividad antagonista del sobrenadante libre de células se mantuvo activa. El tratamiento con lisozima, lipasa y catalasa no afectó la actividad antimicrobiana. Sin embargo, la actividad enzimática de la tripsina suprimió la acción inhibitoria del sobrenadante, confirmando la naturaleza proteica del compuesto activo. En ambos casos, el título de la actividad antilisteria no se vio afectado luego de la inducción mediada por nisina o galactosa. La combinación de los sobrenadantes libres de células no exhibió antagonismo o sinergia. Las características bioquímicas y fisicoquímicas de los agentes antilisteria producidos por las cepas seleccionadas sugieren que pueden ser clasificadas como bacteriocinas tipo I o II. Se deben realizar estudios complementarios para determinar el uso potencial de las cepas seleccionadas como cultivos bioprotectores en el control de la seguridad alimentaria.