Decaimiento de coliformes fecales en lagunas aireadas de plantas de tratamiento de aguas residuales en Lima metropolitana / Decay of fecal coliforms in aerated lagoons of wastewater treatment plants in metropolitan Lima

A nivel mundial, el 44% de las aguas residuales domésticas no se tratan de forma segura, la recolección y tratamiento de aguas residuales, se ha convertido en un desafío, particularmente en áreas urbanas de bajos ingresos dentro de los países en desarrollo, donde las aguas residuales pueden fluir sin tratar a transportes de aguas pluviales o canales de drenaje informales. No es raro encontrar efluentes, desechos sólidos, excretas humanas y descargas líquidas de industrias y hospitales en las aguas superficiales de muchas zonas urbanas de los países en desarrollo. El proceso de tratamiento de aguas residuales puede ser llevado en lagunas mediante reacciones tanto oxidativas como reductoras. En la capa superior de la laguna, donde las aguas residuales son aeróbicas, ocurre el mecanismo convencional de la demanda bioquímica de oxígeno aeróbico (DBO) y se produce la oxidación del amoníaco. La capa inferior de la laguna es anaerobia, y en esta zona tiene lugar la digestión de los sólidos del lodo, un intermedio, la zona facultativa permite la respiración con aceptores de electrones terminales distintos del oxígeno, esto permite reacciones como la desnitrificación. Los gases producidos en las zonas inferiores se estabilizan en la zona aeróbica por disolución oxígeno, y esto reduce los problemas de olores. Este estudio tiene como objetivo, estudiar el descenso de coliformes fecales en lagunas aireadas de plantas de tratamiento de aguas residuales en la ciudad de Lima, Perú. Los resultados señalan que la separación diferencial de las aguas tratadas, experimentó un descenso del 13 al 26% de coleiformes fecales en todas las lagunas de tratamiento(AU)

Globally, 44% of domestic wastewater is not treated safely, and wastewater collection and treatment has become a challenge, particularly in low-income urban areas within developing countries, where wastewater may flow untreated into stormwater conveyances or informal drainage channels. It is not uncommon to find effluents, solid wastes, human excreta, and liquid discharges from industries and hospitals in the surface waters of many urban areas in developing countries. The wastewater treatment process can be carried out in lagoons through both oxidative and reductive reactions. In the upper layer of the lagoon, where the wastewater is aerobic, the conventional mechanism of aerobic biochemical oxygen demand (BOD) occurs and ammonia oxidation occurs. The lower layer of the lagoon is anaerobic, and in this zone the digestion of the sludge solids takes place, an intermediate, the facultative zone allows respiration with terminal electron acceptors other than oxygen, and this allows reactions such as denitrification. The gases produced in the lower zones are stabilized in the aerobic zone by dissolving oxygen, and this reduces odor problems. The objective of this study is to study the decrease of fecal coliforms in aerated lagoons of wastewater treatment plants in the city of Lima, Peru. The results indicate that the differential separation of the treated waters experienced a decrease from 13 to 26% of fecal coleiforms in all treatment lagoons(AU)

Synthesis and characterization of nanoparticles and composites as bactericides.

In the present study, SiO2-TiO2 hybrid nanomaterial and zeolite-TiO2 (Z-TiO2) composites were synthesized by the sol-gel method. Then, the antibacterial activity of the above-mentioned synthesized materials, SiO2 and zeolite (Z) was investigated by the disk diffusion method using Echerichia coli and Enterobacter aerogenes as test microorganisms. All the materials showed antibacterial activity against E. coli with 7.2, 10.7, 3.5 and 8.2 mm of inhibition zone for SiO2-TiO2 hybrid nanomaterial, SiO2, zeolite and Z-TiO2 composite, respectively. However, none of them showed antibacterial activity against E. aerogenes. The obtained results pointed out that these natural-based materials (i.e. Z, SiO2, Z-TiO2 and SiO2-TiO2), known to be noncarcinogenic and nontoxic, can be used as disinfectants against E. coli (an important indicator of the bacteriological quality of water) as safe and eco-friendly alternatives to chlorine.

Expression and purification of L-asparaginase from Escherichia coli and the inhibitory effects of cyclic dipeptides.

L-asparaginase, a key enzyme involved in nitrogen metabolism, is an effective anti-tumour agent. Cyclic dipeptides, a group of compounds, contain several important biological functions. In this paper, we proposed a novel method for L-asparaginase expression and purification from Echerichia coli and determined the effect of cyclic dipeptides on the enzymatic activity of recombinant L-asparaginase. The gene ansB encoding L-asparaginase was amplified from the genome of E. coli BL21 (DE3) by polymerase chain reaction and sub-cloned into pET-15b vector to construct expressing plasmid pET-15b-ansB. The expression of recombinant protein was purified by affinity chromatography using a nickel resin followed by anion exchange chromatography. The purity and quality of the recombinant L-asparaginase were optimised. The results indicated that km for the recombinant L-asparaginase was 3.02 × 10-4 mol/L. Both cyclo-(Pro-Tyr) and cyclo-(Pro-Phe) could inhibit the activity of recombinant L-asparaginase at the level of 10-5 mol/L.

Profile resistance of pathogens causing urinary tract infection in the pediatric population, and antibiotic treatment response, at a University Hospital 2010-2011 / Perfil de resistencia de los patógenos causantes de infección urinaria en la población pediátrica y respuesta al tratamiento antibiótico, en un hospital universitario 2010-2011

Abstract Background: Urinary tract infection (UTI) is one of the most common bacterial infections in childhood and causes acute and chronic morbidity as hypertension and chronic kidney disease. Objectives: To describe the demographic characteristics, infectious agent, antibiotic resistance patterns and empiric therapy response of UTI in pediatric population. Methods: This is a descriptive, retrospective study. Results: Were included 144 patients, 1:2.06 male to female ratio. The most common symptom was fever (79.9%) and 31.3% had history of previous UTI. 72.0% of the patients had positive urine leukocyte count (>5 per field), urine gram was positive in 85.0% of samples and gram negative bacilli accounted for 77.8% for the total pathogens isolated. The most frequent uropathogens isolated were Escherichia coli and Klebsiella pneumoniae. Our E.coli isolates had a susceptibility rate higher than 90% to most of the antibiotics used, but a resistance rate of 42.6% to TMP SMX and 45.5% to ampicillin sulbactam. 6.3% of E. coli was extended-spectrum beta-lactamases producer strains. The most frequent empirical antibiotic used was amikacin, used in 66.0% of the patients. 17 of 90 patients who undergone voiding cistouretrography (VCUG) had vesicoureteral reflux. Conclusion: This study revealed that E. coli was the most frequent pathogen of community acquired UTI. We found that E. coli and other uropathogens had a high resistance rate against TMP SMX and ampicillin sulbactam. In order to ensure a successful empirical treatment, protocols should be based on local epidemiology and susceptibility rates.

Resumen Antecedentes: La infección del tracto urinario (ITU) es una de las infecciones bacterianas más frecuentes en la infancia, se asocia con alta morbilidad aguda y de enfermedades a largo plazo como hipertensión arterial e insuficiencia renal crónica. Objetivo: Describir las características demográficas, agente etiológico, perfil de sensibilidad y respuesta al tratamiento empírico de una población pediátrica. Métodos: Estudio descriptivo, retrospectivo realizado en el Hospital Pablo Tobón Uribe (HPTU), Medellín (Colombia), entre enero de 2010 y diciembre de 2011. Resultados: Se incluyeron 144 pacientes, con una relación hombre: mujer de 1:2.06. El 79.9% consultó por fiebre objetiva y el 31.3% había tenido un episodio de ITU previa. El 72.0% presentó leucocituria y el gram de gota de orina sin centrifugar fue positivo en el 86.0% (77.8% de bacilos con tinción de gram negativos). Los uropatógenos más frecuentes fueron Escherichia coli y Klebsiella pneumoniae. Escherichia coli tuvo una sensibilidad mayor al 90% para la mayoría de antibióticos, excepto en el de trimetropín sulfametoxazol, con una resistencia del 42.6% y del 45.5% a la ampicilina sulbactam. Se usó la amikacina como tratamiento empírico en el 66.0%. En 17 de 90 pacientes se encontró algún grado de reflujo vesicoureteral (RVU). Conclusión: La elección del tratamiento empírico precoz debe basarse en el conocimiento de la epidemiología y el perfil de sensibilidad y resistencia de cada institución. En este estudio se encontró elevado porcentaje de resistencia de la E. coli y otros uropatógenos a trimetropín sulfametoxazol y ampicilina sulbactam.