Impact of socioeconomic inequalities on dental caries in deprived children: a multilevel analysis.

OBJECTIVES: Inequalities have been reported between high, middle and low socioeconomic position (SEP) children. However, the effect of contextual and individual SEP on existing inequalities among socioeconomically deprived children varies between local contexts. The aim of this study was to assess the impact of contextual and individual SEP on individual caries experience among socioeconomically deprived children in Chile. METHODS: Cross-sectional multilevel analysis of data from the 2015 electronic register of the National Board of School Aid and Scholarships (JUNAEB) of Chile. The contextual variables were the municipality Human Development Index (HDI) and rurality index. Individual variables included gender, living in extreme poverty and school grade. Multilevel negative binomial models assessed their impact on DMFT/dmft. RESULTS: 112,429 children in 255 municipalities were included. Overall, contextual SEP (HDI) was not associated with caries experience in the primary or permanent dentition. Individual SEP (living in extreme poverty) was associated with caries experience in both dentitions. The proportion of children living in extreme poverty with caries experience in the primary teeth was 17% higher than children not living in extreme poverty (PR 1.17; 95% CI 1.15-1.19), while for children with permanent teeth it was 9% higher (PR 1.09; 95% CI 1.08-1.11). CONCLUSION: These findings could support the development of health strategies focused on individual SEP to efficiently reduce oral health inequalities among socioeconomically deprived children.

Root anatomy and canal configuration of maxillary premolars: a cone-beam computed tomography study / Anatomía de la raíz y configuración del conducto de los premolares maxilares: estudio de tomografía computarizada de haz cónico

SUMMARY: The aim of the study was to determine the number and anatomical configuration of roots and root canals of maxillary first and second premolars using cone-beam computed tomography scans. n273 CBCT scans were evaluated, obtaining a sample of 592 maxillary premolars. Root number and root canal anatomy were categorized using Ahmed´s classification. Data was analyzed using Pearson's Chi-squared test. Two roots were present on 157 first premolars, one root in 132 premolars and three roots in 17. Second premolars presented one root in 266 samples and two roots in 20; no second premolars presented three roots. Eight different configurations were found; the most frequent was 2MP B1 P1 in first premolars (51,3 %) and 1MP1 (63.6 %) in second premolars. The most frequent morphology found in maxillary premolars in Chilean population was two and three roots. The analysis of internal anatomy using CBCT revealed a highly variable distribution of root canals, generally of low to medium complexity, similar to what is found in other ethnic groups.

RESUMEN: El objetivo de este estudio fue determinar el número y la configuración de raíces y canales radiculares de primeros y segundos premolares maxilares utilizado tomografía computacional de haz cónico. 273 TCHC fueron evaluados, obtenido una muestra de 592 premolares maxilares. El número de raíces y la anatomía de los canales radiculares fueron categorizados utilizando la clasificación de Ahmed. Los datos fueron analizados con la prueba Chi- Cuadrado de Pearson. Dos raíces fueron observadas en 157 primeros presentaron una raíz en 266 muestras y dos raíces en 20; no se encontraron tres raíces en segundos premolares. Ocho diferentes configuraciones fueron encontradas; siendo la más frecuente 2MP B1 P1 en primeros premolares (51,3 %) y 1MP1 (63,6 %) en segundos premolares. La morfología radicular más frecuentemente encontrada en premolares de población Chilena fue de dos y tres raíces. El análisis de la anatomía interna usando TCHC mostró una gran variabilidad de en la distribución de los canales radiculares. Generalmente de mediana y baja complejidad como los encontrados en otros grupos etnicos.

Root morphology of mandibular molars: a cone-beam computed tomography study.

BACKGROUND: The aim of the study was to assess the number and anatomical classification of roots and root canals of first and second mandibular molars using cone-beam computed tomography (CBCT) in a Chilean population. MATERIALS AND METHODS: This study evaluated the CBCT scans of 289 patients aged between 14 and 86 years, obtaining a sample of 1022 mandibular first and second molars. The number of roots and root canals was evaluated according to the anatomical classification proposed by Ahmed in 2016. Data were analysed using Pearson's chi-squared test and ANOVA. RESULTS: Nine hundred fifty-one (93.05%) molars had two roots, while the remaining 71 (6.95%) molars had one root. The most frequent root and root canal morphologies found were: ²MM M² D¹ (29.65%), ²MM M²â»¹ D¹ (22.3%) and ²MM M¹ D¹ (13.4%) (M - mesial, D - distal), with a total of 32 different anatomical distributions. C-shaped canals were present in 56 molars and were more frequently found in women than in men (7.1% vs. 3.88%; p = 0.024). CONCLUSIONS: The analysis of internal anatomy using CBCT revealed a highly variable distribution of root canals. The most frequent morphology found in mandibular molars in a Chilean population was two roots and three canals.

Evaluation of substantivity of hypochlorous acid as an antiplaque agent: A randomized controlled trial.

BACKGROUND: Hypochlorous acid (HOCl) is a non-antibiotic antimicrobial substance with significant effects on pathogenic oral micro-organisms. The effects of HOCl as an antiplaque agent have not been studied. OBJECTIVE: The aim of this study was to evaluate the substantivity of HOCl mouthwashes compared with chlorhexidine (CHX) rinses and a placebo. MATERIALS AND METHODS: A double-blind randomized controlled trial with 75 participants was conducted. Participants were divided into five groups using block randomization: 0.025% HOCl, 0.05% HOCl, 0.12% CHX, 0.2% CHX, and sterile water as a placebo. Participants were instructed to use each rinse solution for 30 seconds after dental prophylaxis. Samples of saliva were taken at baseline and after 30 seconds, 1, 3, 5 and 7 hours to assess substantivity, and bacterial viability was established by the fluorescence method. Visible plaque in all participants was assessed with the Turesky index at baseline and at 7 hours, and adverse events were also assessed. RESULTS: HOCl led to a 33% reduction in bacterial counts in the saliva after 30 seconds compared with a 58% reduction by CHX. HOCl has no substantivity, and bacterial counts returned to baseline after 1 hour. Placebo treatment led to the highest plaque count after 7 hours compared with the CHX and HOCl groups, although the differences were not significant. HOCl rinsing induced the highest percentages of unpleasant taste and dryness sensations. CONCLUSIONS: HOCl rinses have an initial effect on bacterial viability in saliva but have no substantivity. Other mechanisms may explain its antiplaque effect.

Fisiopatología de la nefropatía diabética: una revisión de la literatura / Pathophysiology of diabetic nephropathy: a literature review

La enfermedad renal crónica es una complicación frecuente en la diabetes mellitus. Su importancia radica en la alta prevalencia y la proyección a futuro que ésta tiene. Se asocia a altos gastos en salud y además a deterioro cardiovascular global. La fisiopatología del desarrollo de esta enfermedad está siendo estudiada y se sabe que en ella participan una serie de vías moleculares complejas que determinan una enfermedad microvascular. En esta revisión se intenta abordar las vías conocidas en el desarrollo de nefropatía diabética, con el fin de comprender mejor posibles blancos terapéuticos que se podrían desarrollar.

Chronic kidney disease is a common complication of diabetes. Its importance lies in its high prevalence and future projection. It is associated with high health costs and global cardiovascular deterioration as well. The development of this disease pathophysiology is being studied and it is known that a series of complex molecular pathways determining a microvascular disease are involved. This review addresses the known pathways in the development of diabetic nephropathy aiming to improve the understanding of potential therapeutic targets that could be developed in the future.

Assessment of Mesial Root Morphology and Frequency of MB2 Canals in Maxillary Molars using Cone Beam Computed Tomography / Determinación de la Morfología de la Raíz Mesial y la Frecuencia del Canal MB2 en Molares Maxilares usando Tomografía Computadorizada de Haz Cónico

The aim of this study was to assess the morphology of the mesial root canal system of maxillary molars and the frequency of MB2 canals using cone-beam computed tomography (CBCT). A total of 1374 teeth, first maxillary (1MS, n= 802) and second maxillary molars (2SM, n= 572) of 508 Chilean patients between 8 to 77 years were evaluated through CBCT. The mesiobuccal root was evaluated in all three thirds. Root canal morphology was classified according to Vertucci's method. Data were analyzed by Pearson's Chi-square and Cuzick trend tests. MB2 canal frequency in 1MS was 73.44% and in 2MS 42.48%. The most frequent morphology in 1MS and 2MS were Vertucci type II and I, respectively. No statistically significant association was found between frequencies and side or according to gender (P>0.05). A positive association was found as the age increased in both 1MS and 2MS (P<0.001 and P= 0.023, respectively). Given the anatomical complexity of the mesiobuccal root and the frequent presence of the MB2 canal, the clinician must assume the existence of two canals in this root. CBCT scanning is a good way to initially identify this canal in the different root thirds.

Determinar la morfología del sistema de canales de la raíz mesial de molares maxilares y la frecuencia del canal MB2 usando tomografía computadorizada de haz cónico (TCHC). Un total de 1374 dientes, primeros molares maxilares (1MS, n= 802) y segundos molares maxilares (2MS, n= 572) de 508 pacientes Chilenos entre 8 y 77 años fueron evaluados a través de la TCHC. Se evaluó la raíz mesiobucal en todos sus tercio. La clasificación de Vertucci fue utilizada para determinar la morfología del sistema de canales. Los datos fueron analizados con los test Chi-Cuadrado de Pearson y la prueba de tendencia de Cuzick. La frecuencia del canal MB2 para el 1MS fue 73,44% y el 2MS 42,48%. La morfología mas frecuente en el 1MS y 2MS fueron el tipo II y I de Vertucci, respectivamente. No se encontró asociación significativa entre la frecuencia y el lado o sexo (p>0,005). Una asociación positive fue encontrada a medida que aumentaba la edad en ambos 1MS y 2MS (p<0,001 y p= 0,023, respectivamente). Dada la complejidad de la anatomía de la raíz mesiobucal y la frecuente presencia del canal MB2, el clínico debe asumir la existencia de dos canales en esta raíz. La TCHC es una buena manera de identificar tempranamente el canal en los diferentes tercio radiculares.

Validity and reliability of the T-Scan(®) III for measuring force under laboratory conditions.

Although measuring bite force is an important indicator of the health of the masticatory system, few commercially available transducers have been validated for routine clinical use. T-Scan(®) III Occlusal Analysis System allows to record the bite force distribution, indicating its relative intensity and occlusal timing. Nevertheless, even fewer studies have evaluated the validity and reliability of the latest generation of the T-Scan(®) occlusal analysis system. To determine the validity and reliability of the T-Scan(®) III system when measuring total absolute bite force under laboratory conditions. Known forces were applied to 18 T-Scan(®) III sensors, which were classified into two groups differentiated by their production series. Both Lin's concordance correlation coefficient (CCC) and the intra-class correlation coefficient (ICC) were used to assess the system's reliability and validity. Considering all the sensors studied, a substantial level (Lin's CCC 0·969) and a very good level of reliability (CCI 0·994) were obtained. When evaluating the validity of the system, a poor (Lin's CCC 0·530) and moderate (ICC 0·693) agreement were also obtained. The main factor that negatively influenced the validity of the T-Scan(®) III under these study conditions was the significant difference in the behaviour of the two sensor groups. The T-Scan(®) III showed a high degree of reliability when used to perform consecutive measurements. However, the system showed an insufficient degree of validity for measuring absolute force when estimating total occlusal force under laboratory conditions.

Morphology of the physiological apical foramen in maxillary and mandibular first molars / Morfología del foramen fisiológico apical en primeros molares maxilares y mandibulares

Information regarding the anatomy of the physiological apical foramen is limited. Knowing its diameter and shapes contributes to clinical work, specifically to the cleaning and shaping of the apical third. The aim of this ex vivo study was to determine the minimum and maximum diameters and shape of the physiological apical foramen in the roots of maxillary and mandibular first molars. A descriptive study was conducted on 89 recently extracted first molars. Roots 3-5 mm from the apex were sectioned and prepared for analysis at 40x magnification. The minimum and maximum diameters of each physiological foramen were measured using the program Motic Images plus 2.0 ML. The shape of the foramina, classified as round, oval or irregular, was determined by the difference between the maximum and minimum diameters. A total of 174 physiological foramina were analyzed. The average of the minimum and maximum diameters was between 0.24-0.33 mm in maxillary first molars and between 0.25-0.33 mm in mandibular first molars. In maxillary molars, the most common shape of the foramen was oval (50%), then irregular (32%), then round (18%). In mandibular molars, the oval shape was also the most frequent (59%), followed by irregular (23%) and round (18%). The findings of this study regarding the morphology of physiological apical foramina in first molars make it easier for the operator to choose the appropriately-sized instruments to perform endodontic therapy successfully.

La información relacionada a la anatomía del foramen fisiológico apical es limitada. Conocer su diámetro y forma contribuye al trabajo clínico, específicamente en los procedimientos de limpieza y conformación del tercio apical. El objetivo de este estudio ex vivo fue determinar los diámetros menor, mayor y la forma del foramen fisiológico apical en las raíces de primeros molares maxilares y mandibulares. Se realizó un estudio descriptivo sobre 89 primeros molares recientemente extraídos. Se seccionaron las raíces a 3­5 mm del ápice y fueron preparadas para su análisis bajo magnificación de 40X. Se midieron los diámetros mayor y menor de cada foramen fisiológico mediante el programa Motic Images plus 2.0 ML. La forma de los forámenes fue determinada de acuerdo a la diferencia entre diámetro mayor y menor, clasificándose como redondo, oval o irregular. Un total de 174 forámenes fisiológicos fueron analizados. El promedio del diámetro menor y mayor fue entre 0,24­0,33 mm en primeros molares maxilares y entre 0,25­0,33 mm en primeros molares mandibulares. En molares maxilares, la forma del foramen más común fue la oval (50%), luego irregular (32%) y redonda (18%). En molares mandibulares, la forma oval también fue la más frecuente (59%), seguida por la irregular (23%) y redonda (18%). Los hallazgos de este estudio en relación a morfología de los forámenes fisiológicos apicales en primeros molares, permite al operador facilitar la elección de instrumentos del calibre adecuado para realizar con éxito la terapia endodóntica.

Long-term evaluation and clinical outcomes of children with dental transplants in Temuco city, Chile.

AIM: To assess the clinical and radiographic outcomes of 36 transplanted teeth and the possible factors affecting the results. MATERIALS AND METHODS: In 26 children, 36 teeth transplants were performed. The main reason for transplantations was the loss of anterior teeth due to trauma; 80.5% of transplanted teeth were immature bicuspids. The transplants were clinically and radiolographycally monitored in respect of pulp vitality, root canal obliteration, periradicular changes and root formation. Fisher Exact Test and Kaplan-Meier analyses were performed to determine the association between the variables and estimation of survival rates, respectively. RESULTS: Thirty (83.3%) of the transplantations were recorded as successful and six as unsuccessful (16.7%). The survival rate was 97.2% during average time of 47.5 months ± 27.8 SD. Only one tooth had been extracted and 5 had survived in not ideal conditions. The majority of immature transplanted teeth developed pulp canal obliteration. CONCLUSION: Factors associated to successful outcome were immature root formation of donor tooth and short flexible splinting period. The main factor associated to failure was replacement resorption. The surgical technique did not present statistical significance in the clinical outcome. Tooth transplantation has shown high success and survival rates, and should be considered as a real option in growing patients.

Morphology of the Physiological Apical Foramen in Maxillary and Mandibular First Molars.

Information regarding the anatomy of the physiological apical foramen is limited. Knowing its diameter and shapes contributes to clinical work, specifically to the cleaning and shaping of the apical third. The aim of this ex vivo study was to determine the minimum and maximum diameters and shape of the physiological apical foramen in the roots of maxillary and mandibular first molars. A descriptive study was conducted on 89 recently extracted first molars. Roots 3-5 mm from the apex were sectioned and prepared for analysis at 40× magnification. The minimum and maximum diameters of each physiological foramen were measured using the program Motic Images plus 2.0 ML. The shape of the foramina, classified as round, oval or irregular, was determined by the difference between the maximum and minimum diameters. A total of 174 physiological foramina were analyzed. The average of the minimum and maximum diameters was between 0.24-0.33 mm in maxillary first molars and between 0.25-0.33 mm in mandibular first molars. In maxillary molars, the most common shape of the foramen was oval (50%), then irregular (32%), then round (18%). In mandibular molars, the oval shape was also the most frequent (59%), followed by irregular (23%) and round (18%). The findings of this study regarding the morphology of physiological apical foramina in first molars make it easier for the operator to choose the appropriately-sized instruments to perform endodontic therapy successfully.

Methylene blue removal from contaminated waters using heterogeneous catalytic ozonation promoted by natural zeolite: mechanism and kinetic approach.

This paper presents experimental results of a methylene blue removal system based on heterogeneous catalytic ozonation in the presence of natural zeolite. The effect of pH (2-10) and the presence of radical scavengers (acetate ions) on homogeneous and heterogeneous ozonation systems are assessed at laboratory scale. Results show that heterogeneous catalytic ozonation using natural zeolite increases methylene blue removal rate with respect to the single ozonation process at all pH values. The inhibitory effect of free-radical scavengers is impaired by zeolite, suggesting that methylene blue oxidation reactions take place mainly on the zeolite surface. The increase in methylene blue removal rate could be related to ozone interaction with hydroxyl groups present on the zeolite surface (S--OH2(+), S--OH, S--O(-)), which plays a key role in the reaction mechanism.

BTX abatement using Chilean natural zeolite: the role of Brønsted acid sites.

In wastewater treatment facilities, air quality is not only affected by conventional unpleasant odour compounds; toxic volatile organic compounds (VOCs) are also found. In this study, the adsorptive capacity of Chilean natural zeolite toward VOC removal was evaluated. Moreover, the influence of zeolite chemical surface properties on VOC elimination was also investigated. Three modified zeolite samples were prepared from a natural Chilean zeolite (53% clinoptilolite, 40% mordenite and 7% quartz). Natural and modified zeolite samples were characterised by nitrogen adsorption at 77 K, elemental analyses and X-ray fluorescence (XRF). Chemical modifications of natural zeolite showed the important role of Brønsted acid sites on the abatement of VOCs. The presence of humidity has a negative effect on zeolite adsorption capacity. Natural zeolites could be an interesting option for benzene, toluene and xylene vapour emission abatement.

[Cutaneous mucormycosis in an immunocompromised patient]. / Mucormicosis cutánea en un paciente inmunocomprometido.

Mucormycosis is an increasingly emerging life-threatening infection and is an important cause of morbidity and mortality in patients with leukemia. We present the case of a 4-year-old boy with an acute lymphoblastic leukemia complicated by severe and prolonged neutropenia during induction chemotherapy, who developed cutaneous mucormycosis of the elbow. Direct microscopy with KOH and the histopathologic observation of the skin revealed fungal hyphae without septations. The cultures were positive for Rhizopus microsporus var oligosporus. The patient was treated succefully with amphotericin B during 40 days, surgical debridement and dermoepidermic graft. Early recognition and prompt intervention with combined medical and surgical treatment may improve the outcome. The most common management strategy in survivors involves a combination of antifungal therapy with amphotericin B and surgical debridement.

Mucormicosis cutánea en un paciente inmunocomprometido / Cutaneous mucormycosis in an immunocompromised patient

Mucormycosis is an increasingly emerging life-threatening infection and is an important cause of morbidity and mortality in patients with leukemia. We present the case of a 4-year-old boy with an acute lymphoblastic leukemia complicated by severe and prolonged neutropenia during induction chemotherapy, who developed cutaneous mucormycosis of the elbow. Direct microscopy with KOH and the histopathologic observation of the skin revealed fungal hyphae without septations. The cultures were positive for Rhizopus microsporus var oligosporus. The patient was treated succefully with amphotericin B during 40 days, surgical debridement and dermoepidermic graft. Early recognition and prompt intervention with combined medical and surgical treatment may improve the outcome. The most common management strategy in survivors involves a combination of antifungal therapy with amphotericin B and surgical debridement.

La mucormicosis es una enfermedad emergente grave, producida por hongos saprófitos del orden Mucorales, que afecta fundamentalmente a pacientes inmunocom-prometidos. La forma cutánea se origina por inoculación de esporas dentro de la dermis con el subsecuente desarrollo de una lesión tipo ectima, generalmente única y de evolución rápidamente progresiva, por las características angioinvasoras del hongo, que determina amplias zonas de infartos y necrosis en los tejidos. Presentamos el caso de un paciente con cuatro años de edad, con diagnóstico de leucemia linfoblástica aguda, en quimioterapia de inducción, que cursó con neutropenia profunda y prolongada, presentando una lesión cutánea en el codo compatible con ectima gangrenoso. Recibió tratamiento antimicrobiano y antifúngico, asociado a un aseo quirúrgico. El cultivo para hongos demostró crecimiento de Rhizopus microsporus var oligosporus, y la histología concluyó presencia de hifas no septadas. El estudio de extensión descartó compromiso óseo, sinusal y cerebral. Completó 40 días de terapia antifúngica con anfotericina B deoxicolato, evolucionando satisfactoriamente. Posteriormente requirió injerto dermo-epidérmico. Si bien esta patología es infrecuente, debemos sospecharla en pacientes con neoplasias hematológicas, para establecer un diagnóstico etiológico oportuno, ya que el tratamiento contempla el desbridamiento quirúrgico precoz asociado a antifúngicos sistémicos, siendo de elección anfotericina B.

Arsenic mobilization by epilithic bacterial communities associated with volcanic rocks from Camarones River, Atacama Desert, northern Chile.

The arsenic biogeochemical cycle is greatly dependent on microbial transformations that affect both the distribution and mobility of arsenic species in the environment. In this study, a microbial biofilm from volcanic rocks was characterized on the basis of its bacterial composition and ability to mobilize arsenic under circumneutral pH. Biofilm microstructure was analyzed by scanning electron microscopy (SEM)-energy-dispersive spectroscopy (EDS). Strains were isolated from biofilms and identified by 16S rDNA sequences analysis. Arsenic oxidation and reduction capacity was assayed with high-performance liquid chromatography coupled to gaseous formation performing the detection by atomic absortion in a quartz bucket (HPLC/HG/QAAS), and polymerase chain reaction was used to detect aox and ars genes. Bacterial communities associated with volcanic rocks were studied by denaturing gradient gel electrophoresis (DGGE). The SEM-EDS studies showed the presence of biofilm after 45 days of incubation. The relative closest GenBank matches of the DNA sequences, of isolated arsenic-resistant strains, showed the existence of four different genus: Burkholderia, Pseudomonas, Erwinia, and Pantoea. Four arsenite-resistant strains were isolates, and only three strains were able to oxidize >97% of the As(III) present (500 uM). All arsenate-resistant isolates were able to reduce between 69 and 86% of total As(V) (1000 uM). Analysis of 16S rDNA sequences obtained by DGGE showed the presence of four bacterial groups (∝-proteobacteria, γ-proteobacteria, Firmicutes, and Actinobacteria). Experiments demonstrate that epilithic bacterial communities play a key role in the mobilization of arsenic and metalloids speciation.

Heterogeneous catalytic ozonation of cationic dyes using volcanic sand.

This work aims to present experimental results on the treatment of methylene blue contaminated waters using heterogeneous catalytic ozonation promoted by volcanic sand. The effect of pH (2-8), and the presence of radical scavengers (acetate ions) in homogeneous and heterogeneous systems are evaluated at laboratory scale. Heterogeneous catalytic ozonation using volcanic sand increases methylene blue removal rate. In the presence of free radical scavengers, only a 37% reduction on methylene blue removal rate is observed in the heterogeneous system, as compared with 70% when homogeneous ozonation is used. The results obtained here indicate the importance of chemical surface properties on methylene blue oxidation reactions, suggesting that acid surface sites of volcanic sand play a key role on the reaction mechanism.

Pseudomonas arsenicoxydans sp nov., an arsenite-oxidizing strain isolated from the Atacama desert.

A Gram-negative, arsenite-oxidizing bacterial strain, designated VC-1, was isolated from sediment samples from the Camarones Valley in the Atacama Desert, Chile. Strain VC-1 was strictly aerobic, oxidase and catalase positive, rod shaped, of about 5.5 microm in length and 0.5-1.0 microm in diameter. It was motile by means of multiple polar flagella. The phylogenetic reconstruction of the 16S rRNA gene sequence, an MLSA study by concatenating six genes, and DDH studies indicated that the strain differed genotypically from its closest relatives and was therefore recognized as a new species within the genus Pseudomonas. Phenotypic analysis combining metabolic tests, fatty acid profiles and MALDI-TOF profiles of total cell extracts supported the classification of the new species for which we propose the designation Pseudomonas arsenicoxydans sp. nov. The type strain is accessible under the culture collection numbers CCUG 58201(T) and CECT 7543(T).

Isolation of arsenite-oxidizing bacteria from a natural biofilm associated to volcanic rocks of Atacama Desert, Chile.

Arsenic is naturally present in rocks, soil, water, and air. It is released to the environment by natural processes such as volcanic eruptions, and rock erosion. In this study, two arsenite-oxidizing strains were isolated from volcanic rocks obtained from the Camarones Valley, Atacama Desert, Chile. Strains were isolated from biofilms and identified by 16s ARNr sequences analysis. aox genes were detected by RT-PCR. The arsenic oxidation ability was assayed with silver nitrate and HPLC-HG-AAS. Four arsenite-resistant strains were isolated (8 mM). RT-PCR analysis showed the presence of aox genes in UC-2 and UC-6 strains. In addition, UC-2 and UC-6 strains were able to oxidize 90 and 95% arsenite present in the medium to arsenate, at a rate of 9.3 and 9.8 microg ml(-1) h(-1 )respectively. Bicarbonate (HCO(3) (-)) was used as unique carbon source. Finally, the significative oxidation capacity shown by both strains opens the way to further studies aimed at implementing biological systems to treat arsenic rich wastewater.

Methylene blue removal from contaminated waters using O3, natural zeolite, and O3/zeolite.

This paper compares experimental results on methylene blue (MB) removal systems based on ozone oxidation, zeolite adsorption, and simultaneous adsorption-oxidation using ozone in the presence of natural zeolite. The effect of pH (2-8), and the presence of radical scavengers (sodium acetate) on process rates and removal efficiencies are assessed at laboratory scale. The experimental system consisted of a 1 L differential circular flow reactor and an ozone generator rated at 5 g O3/h. Results show that ozone oxidation combined with zeolite adsorption increases the overall MB oxidation rate with respect to ozonation process and zeolite adsorption. In presence of free radical scavenger, only a 25% of reduction on MB removal rate are observed in the simultaneous treatment, as compared with 70% when ozonation treatment is used, suggesting that MB oxidation reactions take mainly place on the zeolite surface.

Arsenic resistant bacteria isolated from arsenic contaminated river in the Atacama Desert (Chile).

In this study, arsenic resistant bacteria were isolated from sediments of an arsenic contaminated river. Arsenic tolerance of bacteria isolated was carried out by serial dilution on agar plate. Redox abilities were investigated using KMnO4. arsC and aox genes were detected by PCR and RT-PCR, respectively. Bacterial populations were identified by RapID system. Forty nine bacterial strains were isolated, of these, 55 % corresponded to the reducing bacteria, 4% to oxidizing bacteria, 8% presented both activities and in 33% of the bacteria none activity was detected. arsC gene was detected in 11 strains and aox genes were not detected. The activity of arsenic transforming microorganisms in river sediment has significant implications for the behavior of the metalloid.