ABSTRACT The objective of this study was to evaluate two Streptomyces spp. probiotic strains (RL8 and N7) and four highly-diluted bioactive compounds (HDBC) in the growth, survival, and modulation of the microbial content in culture water and hepatopancreas of juvenile white shrimp Penaeus vannamei. An experimental design was applied with five treatments in triplicate, including T1: (RL8+N7); T2: [(ViP-7C+ViA-7C) + (PhA-7C+SiT-7C)]; T3: [(ViP-7C+ViA-7C) + (PhA-7C+SiT-7C) + (N7)]; T4: [(ViP-7C+ViA-7C) + (PhA-7C+SiT-7C) + (RL8)] and T5 as the control without actinobacteria or HDBC. T2 showed significant differences (P < 0.5) in height increase compared to the other treated and control groups. The organisms in T2, T3, and T4 recorded higher weight gain compared to T1 and T5. A survival rate from 94.13 ± 2.12 to 99.01 ± 2.45% was obtained with a significant difference (P < 0.05) between T1, T2, and T3, concerning the untreated control (T5). A significant decrease in Vibrio spp. the content was observed in water and shrimp in T1 and T2 concerning the control. The heterotrophic bacterial count in hepatopancreas increased with all treatments compared to T5. Our results suggest a positive synergy between the HDBC mixture [(ViP-7C+ViA-7C) + (PhA-7C+SiT-7C)] and N7 Streptomyces sp. strain, whose probiotic action has been previously demonstrated by improving culture conditions for P. vannamei juveniles in terms of growth, survival, and reduction of potentially pathogenic bacteria.

Resumen: La cepa Streptomyces sp. RL8 fue caracterizada en base a su actividad antagónica frente a hongos fitopatógenos, solubilización de fosfatos, producción de sideróforos, y su efecto en la germinación y crecimiento inicial in vitro de frijol Tépari (Phaseolus acutifolius Gray), bajo condiciones controladas. Se aplicó un diseño experimental completamente al azar con un tratamiento bacteriano basado en RL8 (T) y agua destilada como tratamiento Control (C), con cuatro réplicas por tratamiento y 10 semillas por réplica. Las variables de respuesta estudiadas fueron el porcentaje y tasa de germinación (PG y TG), longitud de tallo y de raíz (LT y LR), biomasa fresca y seca de parte aérea (BFPA y BSPA) y biomasa fresca y seca de raíz (BFR y BSR). RL8 mostró actividad antagónica frente a cuatro fitopatógenos de los cinco evaluados, promovió la producción de sideróforos y la solubilización de fosfatos. A escala experimental se observaron diferencias significativas con respecto al grupo control en PG (65.83 vs 30%), TG (4.16 vs 2.25), LT (3.81 vs 1.65 cm) y LR (5.61 vs 2.13 cm), BFPA (2736.75 vs 18.46.75 mg), BSPA (608.75 vs 361.5 mg), BFR (347.0 vs 115.75 mg) y BSR (101.25 vs 58.25 mg). Estos resultados confirman un efecto positivo de RL8 en la germinación y crecimiento inicial de Phaseolus acutifolius Gray, revelando su potencialidad para ser utilizada en su cultivo orgánico o tradicional. Se sugiere su aplicación a escala piloto y su evaluación como alternativa de producción agroecológica en invernadero y en campo.

Summary: The Streptomyces sp. RL8 strain was characterized based on its antagonistic activity against phytopathogenic fungi, solubilization of phosphates, production of siderophores, and its effect on the germination and initial in vitro growth of Tépari beans (Phaseolus acutifolius Gray), under controlled conditions. A completely randomized experimental design was applied with a bacterial treatment based on RL8 (T) and distilled water as Control treatment (C), with four replicates per treatment and 10 seeds per replicate. The response variables studied were the percentage and germination rate (GP and GR), stem and root length (ST and RL), fresh and dry biomass of aerial part (FBAP and DBAP) and fresh and dry biomass of root (FRB and DRB). RL8 showed antagonistic activity against four phytopathogens of the five evaluated, promoted the production of siderophores and the solubilization of phosphates. On an experimental scale, significant differences were observed with respect to the control group in GP (65.83 vs 30%), GR (4.16 vs 2.25), SL (3.81 vs 1.65 cm) and RL (5.61 vs 2.13 cm), FBAP (2736.75 vs 18.46. 75 mg), DBAP (608.75 vs 361.5 mg), FRB (347.0 vs 115.75 mg) and DRB (101.25 vs 58.25 mg). These results confirm a positive effect of RL8 on the germination and initial growth of Phaseolus acutifolius Gray, revealing its potential to be used in its organic or traditional cultivation. Its application on a pilot scale and its evaluation as an alternative for agroecological production in greenhouse and in the field is suggested.

ABSTRACT The lemon (Citrus aurantifolia) crop is susceptible to attack by phytopathogens, which are controlled with chemical molecules. An alternative to reverse the ecological damage caused by these chemicals is biological control. The aim of this study was to select strains of actinomycetes with antagonistic activity to Colletotrichum gloeosporioides. It was determined the antagonistic activity in vitro of 181 strains of actinomycetes, belonging to the Chemical Bioactive Center's strain, against C. gloeosporioides; as well as, the extracellular enzymatic activity of the strains that showed better antagonistic effect. From the total of evaluated strains, 62 showed antagonistic capacity manifested against C. gloeosporioides, indicating that they have the potential to be evaluated in vitro and in vivo against different lemon phytopathogens.

RESUMEN El cultivo de limón (Citrus aurantifolia) es susceptible al ataque de fitopatógenos, que son controlados con moléculas químicas. Una alternativa para revertir los daños ecológicos causados por estas sustancias químicas es el control biológico. El objetivo del presente estudio fue seleccionar cepas de actinomicetos con actividad antagónica a Colletotrichum gloeosporioides. Se determinó la actividad antagónica in vitro de 181 cepas de actinomicetos, pertenecientes al cepario del Centro de Bioactivos Químicos, contra C. gloeosporioides; así como, la actividad enzimática extracelular de las cepas que exhibieron mejor efecto antagonista. Del total de cepas evaluadas, 62 mostraron capacidad antagónica manifestada contra C. gloeosporioides, indica que tienen el potencial para ser evaluadas in vitro e in vivo contra diferentes fitopatógenos del limón.

ABSTRACT The effect of seed treatment with the actinomycetes strains EA2 and CB14, and their combination, on damping-off incidence caused by Rhizoctonia solani Kühn in Phaseolus vulgaris L. cv. Velasco largo was evaluated under greenhouse conditions. These strains were compared with Trichoderma harzianum A-34, Celest®Top 312 FS and two controls (positive and negative). Inceptisol sterile and non-sterile soil was used under a completely randomized design. The coating seeds with strains were made using 8 % cassava starch. The incidence of R. solani was determined 21 days after sowing. In non-sterile soil, the lowest incidences caused by R. solani were found with Celest®Top 312 FS, which did not significantly differ from the combination of actinomycete strains CB14 + EA2, but yes with the rest of the treatments. In the sterile soil, the lowest percentages of incidences were obtained with the combination of actinomycete strains (CB14 + EA2)

RESUMEN Se evaluó el efecto del tratamiento a las semillas con cepas de actinomicetos (EA2, CB14 y su combinación) sobre la incidencia de la marchitez de las posturas causadas por Rhizoctonia solani Kühn en Phaseolus vulgaris L. cv. Velasco largo en condiciones de casa de cultivo. Se comparó con Trichoderma harzianum A-34, Celest®Top 312 FS y dos controles (positivo y negativo). Se empleó suelo Pardo mullido medianamente lavado estéril y no estéril, bajo un diseño completamente aleatorizado. El tratamiento a la semilla fue realizado por recubrimiento, con almidón de yuca 8 % como adherente. La incidencia por R. solani se determinó a los 21 días posteriores a la siembra de las semillas. En el suelo no estéril se encontraron las menores incidencias provocadas por R. solani con el uso del Celest®Top 312 FS, el cual no difirió de la combinación de actinomicetos CB14+EA2, pero sí respecto al resto de los tratamientos. En el suelo estéril, los menores porcentajes de incidencia se obtuvieron al utilizar la combinación de cepas de actinomicetos (CB14+EA2)

The aim of this study was to evaluate the in vitro activity of furvina against microorganisms isolated from the skin of canines with piodermatitis in of Santa Clara, Cuba. Resistance to antibacterial agents was assessed by the diffusion method in agar and the in vitro activity was evaluated quantitatively by the broth macrodilution method according to international clinical laboratory standards. Fifty multiresistant strains were identified, 47 from the genus Staphylococcus and 3 from Pseudomonas. The Fisher’s exact test showed highly significant sensibility of microorganisms of the genus Staphylococcus to ciprofloxacin. All strains were resistant to at least three antimicrobials. The Minimum Inhibitory Concentration (MIC) for furvina ranged from 2-16 mg/ml where 83.2% of the strains having a MIC of 4-8 mg/mL. The Minimum Bactericidal Concentration (MBC) ranged from 4-32 mg/ml where 86.2% of the isolates oscillating between 8 and 16 mg/ml. All strains showed a MIC50 against furvina of 5.59 µg/ml (4.70-6.48) and a MBC50 of 11.8 µg/ml (10.0-13.6). These results may infer that furvina exhibits an in vitro bactericidal activity against sensitive and resistant bacteria from canine skin lesions

El objetivo del presente fue evaluar la actividad in vitro de la furvina frente a microorganismos aislados de la piel de caninos con piodermitis de la ciudad de Santa Clara, Cuba. La resistencia a los agentes antibacterianos se determinó mediante el método de difusión en agar y la actividad in vitro se evaluó cuantitativamente mediante macrodilución en caldo según procedimientos internacionales. Se identificaron 50 cepas multirresistentes, siendo 47 del género Staphylococcus y 3 del género Pseudomonas. El test exacto de Fisher demostró sensibilidad altamente significativa de los microorganismos del género Staphylococcus para la ciprofloxacina. Todas las cepas fueron resistentes al menos a tres de los antibacterianos enfrentados. Las muestras evaluadas mostraron una Concentración Inhibitoria Mínima (CIM) entre 2-16 mg/ml frente a furvina, destacándose que el 83.2% de las cepas osciló entre 4 y 8 g/ml, y una Concentración Bactericida Mínima (CBM) entre 4-32 mg/ml, resaltando que el 86.2% de los aislados osciló entre 8 y 16 mg/ml. Todas las cepas evaluadas mostraron una CIM50 frente a furvina de 5.59 mg/ml (4.70-6.48) y una CBM50 de 11.8 mg/ml (10.0-13.6). Los resultados permiten inferir que furvina posee una actividad bactericida in vitro frente a las cepas sensibles y resistentes, aisladas de lesiones en la piel de caninos

In the recent times, the race to cope with the increasing multidrug resistance of pathogenic bacteria has lost much of its momentum and health professionals are grasping for solutions to deal with the unprecedented resistance levels. As a result, there is an urgent need for a concerted effort towards the development of new antimicrobial drugs to stay ahead in the fight against the ever adapting bacteria. In the present report, antibacterial classification functions (models) based on the topological molecular computational design-computer aided ‘‘rational’’ drug design (TOMOCOMD-CARDD) atom-based non-stochastic and stochastic bilinear indices are presented. These models were built using the linear discriminant analysis (LDA) method over a balanced chemical compounds dataset of 2230 molecular structures, with a diverse range of structural and molecular mechanism modes. The results of this study indicated that the non-stochastic and stochastic bilinear indices provided excellent classification of the chemical compounds (with accuracies of 86.31% and 84.92%, respectively, in the training set). These models were further externally validated yielding correct classification percentages of 86.55% and 87.91% for the non-stochastic and stochastic bilinear models, respectively. Additionally, the obtained models were compared with those reported in the literature and demonstrated comparable results, although the latter were built over much smaller datasets and with much higher degrees of freedom. Finally, simulated ligand-based virtual screening of 116 compounds, recently identified as potential antibacterials, was performed yielding 86.21% and 83.62% of correct classification, respectively, and thus demonstrating the utility of the obtained TOMOCOMD-CARDD models in the search of novel compounds with desirable antibacterial activity.