Streptococcosis is a bacterial disease in tilapia that produces economic losses, caused mainly by Streptococcus agalactiae and S. iniae. It is treated using oxytetracycline and florfenicol, which when inappropriately used promotes the selection of antibiotic resistance genes (ARGs). The disease has been mainly associated with stress events such as variations in temperature. The aims of the present study were (1) to detect by molecular methods two species of Streptococcus sp. in a tilapia farm, (2) to relate their presence to physicochemical parameters in the culture system, and (3) to detect the presence of ARGs in tilapia tissues and/or ponds. Tilapia grow-out ponds (n = 30) were sampled, collecting 15 individuals per pond. The physicochemical parameters of water were measured in each pond. Per pond, organs such as the liver, spleen, brain, and eyes were collected from each individual. Then, each organ type was pooled with the respective organ of the other individuals, processed for DNA extraction, and used for PCR analyses to determine the presence of S. agalactiae and S. iniae and for the detection of ARGs (tetM, tetO, fexA, and ermB). The correlations between the presence of S. agalactiae and water physicochemical parameters were determined. Sixty percent of the ponds and 46% of the organ pools were positive for S. agalactiae, whereas S. iniae was not detected. The positive samples showed the following resistance genes: tet(O) (29.1%), tet(M) (12.7%), and erm(B) (1.8%). A moderate but significant positive correlation was found between temperature and the presence of S. agalactiae. This work reported the molecular detection of two species of Streptococcus and ARGs, providing information that allows fast and effective control of these pathogens in tilapia farming. In addition, a future complementary study on Streptococcus sp. serotype distribution and antibiotic resistance genes from tilapia cultured in Costa Rica could also contribute to increase the knowledge of S. agalactiae infections in tilapia farming worldwide.

Introducción: La calidad del agua en una cuenca hidrográfica, y su uso potencial, se ven afectados por factores antrópicos y naturales. El río Tárcoles es el receptor final de aguas de la región central de Costa Rica, donde el tratamiento de aguas residuales es inadecuado o inexistente. Objetivo: Evaluar la contaminación del agua en el río y evaluar a los macroinvertebrados como bioindicadores del ecosistema. Métodos: Se realizaron evaluaciones fisicoquímicas, microbiológicas y de macroinvertebrados del agua superficial en cuatro sitios durante doce meses consecutivos, incluidos dos índices de calidad del agua (ICA-NSF y holandés). Hicimos visitas mensuales para la colocación y recolección de sustratos artificiales para macroinvertebrados acuáticos, y visitas bimensuales para la recolección de muestras de agua para análisis ex situ de los parámetros fisicoquímicos y microbiológicos. Además, se caracterizó el uso del suelo en la parte baja de Tárcoles a partir de archivos tipo “raster” de cobertura. Resultados: Algunas variables fisicoquímicas tuvieron concentraciones similares a las informadas para otros ríos costarricenses, mientras que el oxígeno fue inferior. Las variables microbiológicas indicaron altos niveles de contaminación, especialmente en la época de lluvias. En la estación seca, hubo más macroinvertebrados acuáticos, siendo Chironomidae, Oligochaeta e Hydrobiidae los más abundantes. La contaminación de los ríos se clasifica como "incipiente" según el índice holandés y como "calidad media" según el ICA-NSF. Conclusiones: la contaminación del río Tárcoles se debe principalmente a un uso inadecuado del suelo y actividades antrópicas. Recomendamos un plan de gestión de cuencas e investigación sobre la salud del ecosistema y la conservación de especies vulnerables.

The intensity of aggression against intruders by owners of a territory has been related to the type of resources available to an individual within its territory. The influence of perch-site characteristics on aggressive behavior of resident male Norops polylepis in presence of an intruder male was investigated in this study. At each perch site, pairwise encounters were conducted in which the aggressive behavior of resident males was recorded, along with the diameter of the perch and the number of nearby perches. Aggressive behavior of resident males increased on larger perches and to some extent in areas having greater density of nearby saplings. Potential explanations for the high aggressive behavior of N. polylepis on broad perches with high number of neighboring saplings are explored.

Herein, we report the physical, chemical, and biological treatment of wastewater generated in the teaching laboratories at Universidad Nacional, Costa Rica. Initial physicochemical treatment included neutralization and coagulation-flocculation, followed by a biological treatment with fungi (Aspergillus sp. and Penicillium dipodomyicola) or bacterias, the latter were isolated from the sludge from the campus’ wastewater treatment plant and the greywater collection tank at the School of Chemistry. The samples’ pH prior to treatment was ≤ 2, while COD ranged between 3000 and 30 000 mg/L. Gas chromatography-mass spectra analysis indicated the presence of 55 organic compounds in the wastewater, some of which reached undetectable concentrations after treatment. The fungi and the bacterial strain removed up to 50% of the substances, while the toxicity decreased with respect to time of exposure to the treatment. Results support the potential use of these microorganisms as bioremediators. Although the organic compounds were partially removed, the treated wastewater exhibited high toxicity for Daphnia magna (water flea). Further experiments with longer treatment times or other strains might be needed for effective removal of pollutants.

Skin disorders affect millions of people all over the world. There are limited options to treat dermal illnesses such as vitiligo, psoriasis, and atopic dermatitis (eczema). Central American ferns are a potential source of bioactive metabolites against those diseases. Currently, Polypodium leucotomos Poir. (Phlebodium aureum (L.) J. Sm. synonym) is the only one being commercially utilized for this purpose. In this work, we evaluated the concentration of the skin bioactive compounds: quinic and chlorogenic acid, in the extract of 20 wild ferns from Costa Rica. We also evaluated the antimicrobial capabilities of the raw extracts of wild ferns and the sun protection factor (SPF) of the extracts. We found 19 out of 20 have either an important concentration of the compounds mentioned above or antimicrobial properties. Also, most samples result in higher SPF than P. aureum’s rhizome. We also have studied the fern acclimatization, at different shading conditions, finding a significant influence of the culturing conditions on metabolite production. After acclimatization. So far, we demonstrate that various ferns included in this study are a potential source of treatments for skin conditions.