The integrity of rivers is affected by anthropogenic activities at different spatial scales, from basin and landscape levels to the direct effects on the river and aquatic life. Our objective was to study these effects on the subtropical La Pasión River, analyzing environmental, geomorphological, habitat and water quality, and macroinvertebrates. We sampled the dry season (March 2022) because the river presented stable conditions. We selected the most influential variables in each spatial scale and determined their relationship with the indexes of quality characteristics and aquatic life in the river using multivariate statistics. Most sites (≈65%) had medium water and suboptimal habitat quality status, meanwhile half the sites had regular biotic integrity status; without finding coincidence in the quality of the different indexes applied, all sites indicated a high gradient of degradation from the origin to the mouth of the river. The presence of some families (e.g., Culicidae, Chironomidae, Lumbriculidae) indicated organic matter contamination. The main variables that significantly classified the river quality and integrity structure were water flow, turbidity, habitat embeddedness, and sulfates (χ2 = 0.1145, p < 0.01). It is concluded that the affected sites received wastewater without prior treatment and presented physical barriers such as irrigation channels.

RESUMENEn el presente estudio se describen los patrones de resistencia a antibióticos de E. coli aislada de mastitis bovina, así como la presencia de genes de virulencia y de resistencia. A partir muestras de leche obtenidas de vacas con mastitis se aislaron e identificaron a nivel bioquímico y molecular cepas de E. coli, a las cuales se les analizó el perfil de resistencia a antibióticos y mediante PCR se investigó la presencia de genes de virulencia, de resistencia a antibióticos beta-lactámicos, tetraciclina, estreptomicina y quinolonas; así como la presencia de integrones clase 1. El análisis genético reveló que 11.8 % de los aislados de E. coli presentaron el gen de virulencia que codifica para la intimina (eaeA). Por otro lado, todas las E. coli fueron resistentes a uno o más antibióticos, con alta frecuencia de resistencia para tetraciclina, ampicilina y cefalotina. Además, el 73.5 % fueron resistentes a tres o más antibióticos. De 11 genes de resistencia analizados, se confirmó la presencia de siete, distribuidos en el 79.4 % de los aislados bacterianos. De los cuales, blaCTX-M se encontró en 16 aislados, tetB en 11, tetA, strA y strB en 9, qnrB en cuatro y blaTEM en un solo aislado. También, en el 5.9 % de los aislados de E. coli se identificó la presencia de integrones clase 1. En conclusión, se encontraron elevados índices de resistencia en las E. coli aisladas de mastitis bovina. Estas bacterias contienen genes de virulencia relacionados a patógenos de humano; también llevan genes de resistencia a beta-lactámicos, tetraciclina, estreptomicina y quinolonas. PALABRAS CLAVE: Mastitis bovina, E. coli, Resistencia a los antibióticos, Genes de virulencia, PCR. ABSTRACTIn the present study the antibiotic resistance patterns of E. coli isolated from bovine mastitis, as well as the presence of Extended-spectrum β-lactamases (ESBL), tetracycline, streptomycin, and quinolone resistance genes were analyzed. From mastitic cows, milk samples were obtained, of which E. coli were isolated and identified biochemically and confirmed at the molecular level. Genetic analysis revealed that 11.8 % of the E. coli contained a virulence gene encoding intimin (eaeA). All E. coli were resistant to one or more antibiotics, with higher rates of resistance to tetracycline, ampicillin, and cephalothin. In addition, 73.5 % of E. coli were resistant to three or more antibiotics. Of eleven resistance genes analyzed, seven were detected in 79.4 % of the bacterial isolates. Of these, blaCTX-M was found in 16 isolates, tetB in 11, tetA, strA and strB in nine, qnrB in four, and blaTEM in one isolate. About 5.9 % of the E. coli isolates carried class 1 integron integrase gene. In conclusion, a high prevalence of antibiotic resistance in E. coli isolated from bovine mastitis was identified. The bacteria also harbor a virulence gene related to human pathogens and genes conferring resistance to beta-lactam antibiotics, tetracycline, streptomycin, and quinolones.

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