In planta expression of human polyQ-expanded huntingtin fragment reveals mechanisms to prevent disease-related protein aggregation.

In humans, aggregation of polyglutamine repeat (polyQ) proteins causes disorders such as Huntington's disease. Although plants express hundreds of polyQ-containing proteins, no pathologies arising from polyQ aggregation have been reported. To investigate this phenomenon, we expressed an aggregation-prone fragment of human huntingtin (HTT) with an expanded polyQ stretch (Q69) in Arabidopsis thaliana plants. In contrast to animal models, we find that Arabidopsis sp. suppresses Q69 aggregation through chloroplast proteostasis. Inhibition of chloroplast proteostasis diminishes the capacity of plants to prevent cytosolic Q69 aggregation. Moreover, endogenous polyQ-containing proteins also aggregate on chloroplast dysfunction. We find that Q69 interacts with the chloroplast stromal processing peptidase (SPP). Synthetic Arabidopsis SPP prevents polyQ-expanded HTT aggregation in human cells. Likewise, ectopic SPP expression in Caenorhabditis elegans reduces neuronal Q67 aggregation and subsequent neurotoxicity. Our findings suggest that synthetic plant proteins, such as SPP, hold therapeutic potential for polyQ disorders and other age-related diseases involving protein aggregation.

Arabidopsis metacaspase MC1 localizes in stress granules, clears protein aggregates, and delays senescence.

Stress granules (SGs) are highly conserved cytoplasmic condensates that assemble in response to stress and contribute to maintaining protein homeostasis. These membraneless organelles are dynamic, disassembling once the stress is no longer present. Persistence of SGs due to mutations or chronic stress has been often related to age-dependent protein-misfolding diseases in animals. Here, we find that the metacaspase MC1 is dynamically recruited into SGs upon proteotoxic stress in Arabidopsis (Arabidopsis thaliana). Two predicted disordered regions, the prodomain and the 360 loop, mediate MC1 recruitment to and release from SGs. Importantly, we show that MC1 has the capacity to clear toxic protein aggregates in vivo and in vitro, acting as a disaggregase. Finally, we demonstrate that overexpressing MC1 delays senescence and this phenotype is dependent on the presence of the 360 loop and an intact catalytic domain. Together, our data indicate that MC1 regulates senescence through its recruitment into SGs and this function could potentially be linked to its remarkable protein aggregate-clearing activity.

Correction: Differential Subplastidial Localization and Turnover of Enzymes Involved in Isoprenoid Biosynthesis in Chloroplasts.

[This corrects the article DOI: 10.1371/journal.pone.0150539.].

A dimer-monomer switch controls CHIP-dependent substrate ubiquitylation and processing.

The high substrate selectivity of the ubiquitin/proteasome system is mediated by a large group of E3 ubiquitin ligases. The ubiquitin ligase CHIP regulates the degradation of chaperone-controlled and chaperone-independent proteins. To understand how CHIP mediates substrate selection and processing, we performed a structure-function analysis of CHIP and addressed its physiological role in Caenorhabditis elegans and human cells. The conserved function of CHIP in chaperone-assisted degradation requires dimer formation to mediate proteotoxic stress resistance and to prevent protein aggregation. The CHIP monomer, however, promotes the turnover of the membrane-bound insulin receptor and longevity. The dimer-monomer transition is regulated by CHIP autoubiquitylation and chaperone binding, which provides a feedback loop that controls CHIP activity in response to cellular stress. Because CHIP also binds other E3 ligases, such as Parkin, the molecular switch mechanism described here could be a general concept for the regulation of substrate selectivity and ubiquitylation by combining different E3s.

A proteostasis network safeguards the chloroplast proteome.

Several protein homeostasis (proteostasis) pathways safeguard the integrity of thousands of proteins that localize in plant chloroplasts, the indispensable organelles that perform photosynthesis, produce metabolites, and sense environmental stimuli. In this review, we discuss the latest efforts directed to define the molecular process by which proteins are imported and sorted into the chloroplast. Moreover, we describe the recently elucidated protein folding and degradation pathways that modulate the levels and activities of chloroplast proteins. We also discuss the links between the accumulation of misfolded proteins and the activation of signalling pathways that cope with folding stress within the organelle. Finally, we propose new research directions that would help to elucidate novel molecular mechanisms to maintain chloroplast proteostasis.

Correction: Specific Hsp100 Chaperones Determine the Fate of the First Enzyme of the Plastidial Isoprenoid Pathway for Either Refolding or Degradation by the Stromal Clp Protease in Arabidopsis.

[This corrects the article DOI: 10.1371/journal.pgen.1005824.].

[Comprehensive care in type 2 diabetes: from DiabeIMSS to CADIMSS]. / Atención integral en diabetes tipo 2: transición del modelo DiabetIMSS a CADIMSS.

In diabetes, obtaining optimal control is key to reducing chronic complications. Unfortunately, not all patients achieve the recommended goals. Therefore, the challenges to develop and evaluate comprehensive care models are enormous. In October 2008, the Diabetic Patient Care Program (DiabetIMSS) was designed and implemented in family medicine. Its principal component is the multidisciplinary team (doctor, nurse, psychologist, dietitian, dentist, and social worker) that offers coordinated health care; monthly medical consultation and individual, family and group education on self-care and prevention of complications for 12 months. Due to the COVID-19 pandemic, the percentage of attendance at the DiabetIMSS modules decreased significantly. This is how the Medical Director considered it necessary to strengthen them, and the Diabetes Care Centers (CADIMSS) arose. In addition to providing medical care with a comprehensive and multidisciplinary approach, the CADIMSS encourages the co-responsibility of the patient and his family. It consists of monthly medical consultation and nursing staff provides monthly educational sessions for 6 months. Pending tasks remain and there are still areas of opportunity to modernize and reorganize services that contribute to improving the health of the population with diabetes.

En un paciente con diabetes, la obtención de un control óptimo es clave para reducir las complicaciones crónicas. Desafortunadamente, no todos los pacientes logran las metas recomendadas. Por ello, son substanciales los desafíos para desarrollar y evaluar modelos de atención integral. En octubre del 2008, se diseñó e implementó el Programa de Atención al Paciente Diabético (DiabetIMSS) en medicina familiar. Su componente básico es el equipo multidisciplinario (médico, enfermera, psicólogo, dietista, dentista y trabajador social) que ofrece asistencia sanitaria coordinada, consulta médica mensual y educación individual, familiar y grupal sobre autocuidado y prevención de complicaciones durante 12 meses. Debido a la pandemia de COVID-19, el porcentaje de asistencia a los módulos DiabetIMSS disminuyó importantemente. Es así como la Dirección de Prestaciones Médicas consideró necesario su fortalecimiento, por lo que surgen los Centros de Atención a la Diabetes (CADIMSS). Además de proporcionar atención médico-asistencial con enfoque integral y multidisciplinario, en los CADIMSS se fomenta la corresponsabilidad del paciente y su familia, y se otorga consulta médica mensual y sesiones educativas a cargo de personal de enfermería durante 6 meses. Sin embargo, siguen tareas pendientes, y aún hay áreas de oportunidad para modernizar y reorganizar los servicios que contribuyan a mejorar la salud de la población con diabetes.

[PREVENIMSS: a brief overview of its 20 years, challenges and opportunities]. / PREVENIMSS: un breve recorrido de sus 20 años, retos y oportunidades.

Twenty years after its launch, the most ambitious preventive program implemented at the institutional level in Mexico called PREVENIMSS focuses on new challenges and moves towards relaunching. This paper reviews the foundations and design of PREVENIMSS and its evolution throughout these two decades. The PREVENIMS coverage assessment through national surveys set a relevant precedent in evaluating programs at the Mexican Institute of Social Security. PREVENIMSS has shown progress in preventing vaccine-preventable diseases. However, given the current epidemiological profile, there is still a need to provide more effective primary and secondary prevention of chronic noncommunicable diseases. New digital resources and orientation of PREVENIMSS towards a more comprehensive approach that contemplates secondary prevention and rehabilitation can help to face the growing challenges that the program still faces.

A 20 años de su lanzamiento, el programa preventivo más ambicioso implementado a nivel institucional en México llamado PREVENIMSS se enfoca en nuevos desafíos y avanza hacia el relanzamiento. Este artículo hace un breve recorrido de sus fundamentos, diseño y evolución a lo largo de estas dos décadas. La estimación de las coberturas de PREVENIMSS a través de encuestas nacionales también marcó un precedente en la evaluación de programas en el Instituto Mexicano del Seguro Social. PREVENIMSS ha mostrado avances en prevención de enfermedades prevenibles por vacunación, pero aún existe la necesidad de brindar prevención primaria y secundaria más efectivos de las enfermedades crónicas no transmisibles ante el perfil epidemiológico actual. Nuevos recursos digitales y la orientación hacia un enfoque más integral que contemple la prevención secundaria y la rehabilitación pueden ayudar a enfrentar los crecientes desafíos que aún enfrenta el programa.

The intrinsic chaperone network of Arabidopsis stem cells confers protection against proteotoxic stress.

The biological purpose of plant stem cells is to maintain themselves while providing new pools of differentiated cells that form organs and rejuvenate or replace damaged tissues. Protein homeostasis or proteostasis is required for cell function and viability. However, the link between proteostasis and plant stem cell identity remains unknown. In contrast to their differentiated counterparts, we find that root stem cells can prevent the accumulation of aggregated proteins even under proteotoxic stress conditions such as heat stress or proteasome inhibition. Notably, root stem cells exhibit enhanced expression of distinct chaperones that maintain proteome integrity. Particularly, intrinsic high levels of the T-complex protein-1 ring complex/chaperonin containing TCP1 (TRiC/CCT) complex determine stem cell maintenance and their remarkable ability to suppress protein aggregation. Overexpression of CCT8, a key activator of TRiC/CCT assembly, is sufficient to ameliorate protein aggregation in differentiated cells and confer resistance to proteotoxic stress in plants. Taken together, our results indicate that enhanced proteostasis mechanisms in stem cells could be an important requirement for plants to persist under extreme environmental conditions and reach extreme long ages. Thus, proteostasis of stem cells can provide insights to design and breed plants tolerant to environmental challenges caused by the climate change.

The intrinsic proteostasis network of stem cells.

The proteostasis network adjusts protein composition and maintains protein integrity, which are essential processes for cell function and viability. Current efforts, given their intrinsic characteristics, regenerative potential and fundamental biological functions, have been directed to define proteostasis of stem cells. These insights demonstrate that embryonic stem cells and induced pluripotent stem cells exhibit an endogenous proteostasis network that not only modulates their pluripotency and differentiation but also provides a striking ability to suppress aggregation of disease-related proteins. Moreover, recent findings establish a central role of enhanced proteostasis to prevent the aging of somatic stem cells in adult organisms. Notably, proteostasis is also required for the biological purpose of adult germline stem cells, that is to be passed from one generation to the next. Beyond these links between proteostasis and stem cell function, we also discuss the implications of these findings for disease, aging, and reproduction.

Evaluation of Chiapas' HIV/AIDS information system of epidemiological surveillance / Evaluación del Sistema de Información de Vigilancia Epidemiológica de VIH/SIDA en Chiapas

Background: The functionality and performance of a health information system should be evaluated from the perspective of those who develop its processes. Considering the above, this study evaluated the performance of the HIV/AIDS Epidemiological Surveillance System (SIVE VIH/SIDA, according to its initials in Spanish) in Chiapas, Mexico. Methods: Qualitative study on the performance, structure and dynamics of SIVE VIH/SIDA, based on interviews with the personnel participating in this surveillance system, using the Updated Guidelines for the Evaluation of Public Health Surveillance Systems. The analysis was performed through the cyclic interactive method of content analysis, from which the evaluation indices were constructed. Results: A total of 32 interviews were conducted. The structure was described as well defined, at the expense of organizational dimensions, procedures and material resources. The dynamics of information, from the perspective of the collection, processing and use of information, was rated as regular. The performance of the SIVE HIV/AIDS in Chiapas was regular at the expense of these attributes of the information system: simplicity, flexibility, quality of data, acceptability, sensitivity, representativeness, timeliness and stability. Conclusions: In order to improve the performance of SIVE VIH/SIDA, it is necessary to strengthen the human resources and use of information dimensions, so that it can be an instrument for action.

Introducción: la funcionalidad y el desempeño de un sistema de información en salud deben evaluarse desde la perspectiva de quienes desarrollan sus procesos. Considerando lo anterior, este estudio evaluó el desempeño del Sistema de Vigilancia Epidemiológica del Virus de Inmunodeficiencia Humana/Síndrome de Inmunodeficiencia Adquirida (SIVE VIH/SIDA) en Chiapas, México. Métodos: estudio cualitativo sobre el desempeño, la estructura y la dinámica del SIVE VIH/SIDA, el cual se llevó a cabo con base en entrevistas al personal que participa en él, de acuerdo con las Guías Actualizadas para la Evaluación de Sistemas de Vigilancia en Salud Pública de los Centros para el Control y la Prevención de Enfermedades. El análisis se hizo con el método interactivo cíclico del análisis de contenido, a partir de lo cual se construyeron los índices de evaluación. Resultados: se hicieron un total de 32 entrevistas. La estructura fue calificada como bien definida, a expensas de las dimensiones organización, procedimientos y recursos materiales. La dinámica de información, desde la perspectiva de la recolección, el procesamiento y el uso de la información, fue calificada como regular. El desempeño del SIVE VIH/SIDA en Chiapas fue regular a expensas de los atributos simplicidad, flexibilidad, calidad de los datos, aceptabilidad, sensibilidad, representatividad, oportunidad y estabilidad. Conclusiones: para mejorar el desempeño del SIVE VIH/SIDA se requiere fortalecer las dimensiones de recursos humanos y el uso de la información, para que así se constituya en un instrumento para la acción.

Chloroplasts Modulate Elongation Responses to Canopy Shade by Retrograde Pathways Involving HY5 and Abscisic Acid.

Plants use light as energy for photosynthesis but also as a signal of competing vegetation. Using different concentrations of norflurazon and lincomycin, we found that the response to canopy shade in Arabidopsis (Arabidopsis thaliana) was repressed even when inhibitors only caused a modest reduction in the level of photosynthetic pigments. High inhibitor concentrations resulted in albino seedlings that were unable to elongate when exposed to shade, in part due to attenuated light perception and signaling via phytochrome B and phytochrome-interacting factors. The response to shade was further repressed by a retrograde network with two separate nodes represented by the transcription factor LONG HYPOCOTYL 5 and the carotenoid-derived hormone abscisic acid. The unveiled connection among chloroplast status, light (shade) signaling, and developmental responses should contribute to achieve optimal photosynthetic performance under light-changing conditions.

Interference with Clp protease impairs carotenoid accumulation during tomato fruit ripening.

Profound metabolic and structural changes are required for fleshy green fruits to ripen and become colorful and tasty. In tomato (Solanum lycopersicum), fruit ripening involves the differentiation of chromoplasts, specialized plastids that accumulate carotenoid pigments such as ß-carotene (pro-vitamin A) and lycopene. Here, we explored the role of the plastidial Clp protease in chromoplast development and carotenoid accumulation. Ripening-specific silencing of one of the subunits of the Clp proteolytic complex resulted in ß-carotene-enriched fruits that appeared orange instead of red when ripe. Clp-defective fruit displayed aberrant chromoplasts and up-regulated expression of nuclear genes encoding the tomato homologs of Orange (OR) and ClpB3 chaperones, most probably to deal with misfolded and aggregated proteins that could not be degraded by the Clp protease. ClpB3 and OR chaperones protect the carotenoid biosynthetic enzymes deoxyxylulose 5-phosphate synthase and phytoene synthase, respectively, from degradation, whereas OR chaperones additionally promote chromoplast differentiation by preventing the degradation of carotenoids such as ß-carotene. We conclude that the Clp protease contributes to the differentiation of chloroplasts into chromoplasts during tomato fruit ripening, acting in co-ordination with specific chaperones that alleviate protein folding stress, promote enzyme stability and accumulation, and prevent carotenoid degradation.

Interference with plastome gene expression and Clp protease activity in Arabidopsis triggers a chloroplast unfolded protein response to restore protein homeostasis.

Disruption of protein homeostasis in chloroplasts impairs the correct functioning of essential metabolic pathways, including the methylerythritol 4-phosphate (MEP) pathway for the production of plastidial isoprenoids involved in photosynthesis and growth. We previously found that misfolded and aggregated forms of the first enzyme of the MEP pathway are degraded by the Clp protease with the involvement of Hsp70 and Hsp100/ClpC1 chaperones in Arabidopsis thaliana. By contrast, the combined unfolding and disaggregating actions of Hsp70 and Hsp100/ClpB3 chaperones allow solubilization and hence reactivation of the enzyme. The repair pathway is promoted when the levels of ClpB3 proteins increase upon reduction of Clp protease activity in mutants or wild-type plants treated with the chloroplast protein synthesis inhibitor lincomycin (LIN). Here we show that LIN treatment rapidly increases the levels of aggregated proteins in the chloroplast, unleashing a specific retrograde signaling pathway that up-regulates expression of ClpB3 and other nuclear genes encoding plastidial chaperones. As a consequence, folding capacity is increased to restore protein homeostasis. This sort of chloroplast unfolded protein response (cpUPR) mechanism appears to be mediated by the heat shock transcription factor HsfA2. Expression of HsfA2 and cpUPR-related target genes is independent of GUN1, a central integrator of retrograde signaling pathways. However, double mutants defective in both GUN1 and plastome gene expression (or Clp protease activity) are seedling lethal, confirming that the GUN1 protein is essential for protein homeostasis in chloroplasts.

Both Hsp70 chaperone and Clp protease plastidial systems are required for protection against oxidative stress.

Environmental stress conditions such as high light, extreme temperatures, salinity or drought trigger oxidative stress and eventually protein misfolding in plants. In chloroplasts, chaperone systems refold proteins after stress, while proteases degrade misfolded and aggregated proteins that cannot be refolded. We observed that reduced activity of chloroplast Hsp70 chaperone or Clp protease systems both prevented growth of Arabidopsis thaliana seedlings after treatment with the oxidative agent methyl viologen. Besides showing a role for these particular protein quality control components on the protection against oxidative stress, we provide evidence supporting the existence of a yet undiscovered pathway for Clp-mediated degradation of the damaged proteins.

Differential Subplastidial Localization and Turnover of Enzymes Involved in Isoprenoid Biosynthesis in Chloroplasts.

Plastidial isoprenoids are a diverse group of metabolites with roles in photosynthesis, growth regulation, and interaction with the environment. The methylerythritol 4-phosphate (MEP) pathway produces the metabolic precursors of all types of plastidial isoprenoids. Proteomics studies in Arabidopsis thaliana have shown that all the enzymes of the MEP pathway are localized in the plastid stroma. However, immunoblot analysis of chloroplast subfractions showed that the first two enzymes of the pathway, deoxyxylulose 5-phosphate synthase (DXS) and reductoisomerase (DXR), can also be found in non-stromal fractions. Both transient and stable expression of GFP-tagged DXS and DXR proteins confirmed the presence of the fusion proteins in distinct subplastidial compartments. In particular, DXR-GFP was found to accumulate in relatively large vesicles that could eventually be released from chloroplasts, presumably to be degraded by an autophagy-independent process. Together, we propose that protein-specific mechanisms control the localization and turnover of the first two enzymes of the MEP pathway in Arabidopsis chloroplasts.

Specific Hsp100 Chaperones Determine the Fate of the First Enzyme of the Plastidial Isoprenoid Pathway for Either Refolding or Degradation by the Stromal Clp Protease in Arabidopsis.

The lifespan and activity of proteins depend on protein quality control systems formed by chaperones and proteases that ensure correct protein folding and prevent the formation of toxic aggregates. We previously found that the Arabidopsis thaliana J-protein J20 delivers inactive (misfolded) forms of the plastidial enzyme deoxyxylulose 5-phosphate synthase (DXS) to the Hsp70 chaperone for either proper folding or degradation. Here we show that the fate of Hsp70-bound DXS depends on pathways involving specific Hsp100 chaperones. Analysis of individual mutants for the four Hsp100 chaperones present in Arabidopsis chloroplasts showed increased levels of DXS proteins (but not transcripts) only in those defective in ClpC1 or ClpB3. However, the accumulated enzyme was active in the clpc1 mutant but inactive in clpb3 plants. Genetic evidence indicated that ClpC chaperones might be required for the unfolding of J20-delivered DXS protein coupled to degradation by the Clp protease. By contrast, biochemical and genetic approaches confirmed that Hsp70 and ClpB3 chaperones interact to collaborate in the refolding and activation of DXS. We conclude that specific J-proteins and Hsp100 chaperones act together with Hsp70 to recognize and deliver DXS to either reactivation (via ClpB3) or removal (via ClpC1) depending on the physiological status of the plastid.

Functional analysis of the Arabidopsis thaliana CHLOROPLAST BIOGENESIS 19 pentatricopeptide repeat editing protein.

The Arabidopsis thaliana pentatricopeptide repeat (PPR) family of proteins contains several degenerate 35-aa motifs named PPR repeats. These proteins control diverse post-transcriptional regulatory mechanisms, including RNA editing. CLB19 belongs to the PLS subfamily of PPR proteins and is essential for the editing and functionality of the subunit A of plastid-encoded RNA polymerase (RpoA) and the catalytic subunit of the Clp protease (ClpP1). We demonstrate in vitro that CLB19 has a specific interaction with these two targets, in spite of their modest sequence similarity. Using site-directed mutagenesis of the rpoA target, we analyzed the essential nucleotides required for CLB19-rpoA interactions. We verified that, similar to other editing proteins, the C-terminal E domain of CLB19 is essential for editing but not for RNA binding. Using biomolecular fluorescence complementation, we demonstrated that the E domain of CLB19 interacts with the RNA-interacting protein MORF2/RIP2 but not with MORF9/RIP9. An interesting finding from this analysis was that overexpression of a truncated CLB19 protein lacking the E domain interferes with cell fate during megasporogenesis and the subsequent establishment of a female gametophyte, supporting an important role of plastids in female gametogenesis. Together these analyses provide important clues about the particularities of the CLB19 editing protein.

An Uncharacterized Apocarotenoid-Derived Signal Generated in ζ-Carotene Desaturase Mutants Regulates Leaf Development and the Expression of Chloroplast and Nuclear Genes in Arabidopsis.

In addition to acting as photoprotective compounds, carotenoids also serve as precursors in the biosynthesis of several phytohormones and proposed regulatory signals. Here, we report a signaling process derived from carotenoids that regulates early chloroplast and leaf development. Biosynthesis of the signal depends on ζ-carotene desaturase activity encoded by the ζ-CAROTENE DESATURASE (ZDS)/CHLOROPLAST BIOGENESIS5 (CLB5) gene in Arabidopsis thaliana. Unlike other carotenoid-deficient plants, zds/clb5 mutant alleles display profound alterations in leaf morphology and cellular differentiation as well as altered expression of many plastid- and nucleus-encoded genes. The leaf developmental phenotypes and gene expression alterations of zds/clb5/spc1/pde181 plants are rescued by inhibitors or mutations of phytoene desaturase, demonstrating that phytofluene and/or ζ-carotene are substrates for an unidentified signaling molecule. Our work further demonstrates that this signal is an apocarotenoid whose synthesis requires the activity of the carotenoid cleavage dioxygenase CCD4.

[Acute otitis media: could it be a sentinel indicator of health care?]. / Otitis media aguda: ¿indicador centinela de la atención de la salud?

BACKGROUND: Acute otitis media is the most common bacterial disease in children under five years; therefore, is one of the most common causes of pediatric consultation. Our objective was to determine the feasibility to consider this disease as a sentinel factor of medical attention. METHODS: All the new cases of acute otitis media registered between 2008 and 2011 were collected and analyzed. Proportions, ratios, and incidence rates were determined. Also, the limits for proportions were calculated using mid P exact test. RESULTS: In children under five years, we observed 20 % of the cases of non-suppurative otitis media, and suppurative otitis media in 17 %. The reason for acute respiratory infection in relation to cases of otitis media in children of this age increased from 87:1 in 2008 to 53:1 in 2011. CONCLUSIONS: The reason of suppurative otitis media decreased in children under five years, even in 2009, when it was registered the highest number of new cases of acute respiratory infection. It was not feasible to determine if acute otitis media is a sentinel indicator; however, we could monitor medical attention indirectly.

INTRODUCCIÓN: la otitis media aguda es la enfermedad bacteriana más frecuente en los niños menores de cinco años, por lo que constituye una de las causas más comunes de consulta médica pediátrica. El objetivo de esta investigación fue conocer el panorama epidemiológico de la otitis media aguda, con la finalidad de determinar la factibilidad de considerarla un indicador centinela de la atención médica. MÉTODOS: se recolectaron y analizaron todos los casos nuevos de otitis media aguda que se presentaron entre 2008 y 2011. Se determinaron proporciones, razones y tasas de incidencia, y se calcularon los límites para proporciones por prueba exacta de P-media. Resultados: en los niños menores de cinco años de edad se observó 20 % de los casos de otitis media no supurativa y 17 % de los casos de otitis media supurativa. En ese grupo de edad, aumentó la razón de casos de infecciones respiratorias agudas en relación con los de otitis media: 87:1 en 2008 a 53:1 en 2011. CONCLUSIONES: la razón de otitis media supurativa disminuyó en los menores de cinco años, incluso en el año de 2009, cuando se registró el mayor número de casos nuevos de infección respiratoria aguda. No fue factible determinar si la otitis media aguda es un indicador centinela; sin embargo, fue posible monitorear indirectamente la atención médica.