Chemical elements, which are present in drinking water, could vary due to water sources, treatment processes or even the plumbing materials. Most of these elements do not represent a threat, while others, such as heavy metals, have been proven to cause harmful effects over human and aquatic wildlife. In this study, the quality of drinking water in three cities in Ecuador, Quito, Ibarra and Guayaquil was assessed through a multielement analysis and the heavy metal pollution index (HPI). A total of 102 drinking water samples and six natural water samples were collected and analyzed. Within the scope of analysis, results show that water quality complies with local and international guidelines. HPI did not show significant differences in the water that is supplied to the different neighborhoods of the three cities studied. However, actions should be taken to protect the sources of water, especially in Guayaquil, due to the presence of lead and chromium. For instance, lead was found in 2.8% of the samples in concentrations above World Health Organization (WHO) recommended values. Thus, we suggest to assessing the quality and age of the plumbing system within the whole country, in order to avoid drinking water contamination with heavy metals.

Las enfermedades transmitidas por alimentos (ETA’s) son un problema importante en la salud pública y la prevalencia de las mismas permiten conocer la calidad higiénico-sanitaria de los alimentos. Se realizó un estudio descriptivo de corte transversal, en el cuál se muestrearon aleatoriamente 8 sitios de expendio, de los cuales 4 corresponden al denominado sector A (cadenas comerciales) y, los otros 4 del sector B (distribuidores mayoristas) de huevo comercial en la ciudad de Ibarra, es así que se escogieron al azar 10 huevos por sitio de expendio, dando así un total de 80 huevos estudiados. De cada huevo se sustrajo 3 muestras: clara, yema y cascarón; obteniendo un total de 240 muestras que se repartieron en dos grupos, cultivos para Salmonella spp., y Escherichia coli., obteniendo un total de 480 muestras procesadas para cultivo bacteriano aplicando los métodos de la Norma Técnica Ecuatoriana INEN 1529-15 e INEN 1529-8 respectivamente, para el control microbiológico de alimentos. Como resultado del análisis microbiológico se obtuvo un total de 18 muestras positivas, 10 para Salmonella spp., y 8 para Escherichia coli, con ello se procedió a realizar el aislamiento de las colonias en caldo nutritivo para posteriormente realizar la extracción de ADN. Terminada esta etapa se realizó la PCR para la amplificación del gen ADNr 16s, y con ello realizar la técnica RFLP para la detección de polimorfismos. En conclusión, se obtuvo una prevalencia del 4,16% y 3,33% para Salmonella spp., y Escherichia coli; siendo el sector B (distribuidores mayoristas) el de mayor prevalencia, además mediante la secuenciación se detectaron otras especies bacterianas correspondientes a: Pseudomonas sp, Acinetobacter sp, Enterobacter sp. Se identificó dos serotipos para Salmonella spp: S. Enteritidis y S. Typhimurium. El serotipo identificado de la bacteria Escherichia coli fue O157:H7.

The objective of the research was to contrast two methods for the quantification of hexavalent chromium. The first method is the biosensor that from the gene transformation of the cells of Escherichia coli, was incorporated by electroporation the plasmid pTOP Blunt V2, synthesized with luxA genes that provides luminescence through the catalytic activity of the luciferase top and chr genes that give the bacteria resistance to chromium. The second method is the application of the UV-visible colorimetric technique. Chromium was analysed at different concentrations, from 0.05 mg l−1 (maximum allowable limit for human consumption); 0.1 mg l−1; 0.2 mg l−1; 0.4 mg l−1; 0.8 mg l−1 and 1 mg l−1 with 5 replicates, subsequent to this, the two methods of chromium analysis were applied in river samples, thus obtaining that the biosensor in concentrations of 2x106 CFU of E. coli, has a margin of error of 1.4%, a result derived from the coefficient of determination of the absorbance of chromium, unlike the UV-visible method with the colorimetric equipment, which presented a reading error of 3.9%.

Honey bee venom, known as apitoxin, is composed of several peptides, the most important of which is melittin. This peptide is a current focus of research since it can improve the immune system and act against cancer due to its anti-mutagenic, anti-inflammatory, and even contraceptive effects. This makes it very desirable to obtain melittin-producing bacteria, and for this reason, this study has aimed at the cloning of Escherichia coli with the melittin gene from western bee. In order to do this, the total RNA of the western honey bee (Apis mellifera) has been extracted, and a reverse transcription polymerase chain reaction (RTPCR) has been carried out, at different annealing temperatures (68.0, 68.2, 68.4, 68.6, 68.8, and 69.0°C) to amplify the melittin cDNA. The annealing temperature of 68.4°C has allowed the highest production. Subsequently, this cDNA has been cloned into the pGEM-T vector, which has transformed E. coli JM109. This transformation has been corroborated by the blue/white test mediated by X-gal.