No description available.

Background: Acute respiratory infections (ARIs) represent an important cause of morbidity and mortality in children, remaining a major public health concern, especially affecting children under 5 years old from low-income countries. Unfortunately, information regarding their epidemiology is still limited in Peru. Methods: A secondary data analysis was performed from a previous cross-sectional study conducted in children with a probable diagnosis of Pertussis from January 2010 to July 2012. All samples were analyzed via Polymerase Chain Reaction (PCR) for the following etiologies: Influenza-A, Influenza-B, RSV-A, RSV-B, Adenovirus, Parainfluenza 1 virus, Parainfluenza 2 virus, Parainfluenza 3 virus, Mycoplasma pneumoniae and Chlamydia pneumoniae. Results: A total of 288 patients were included. The most common pathogen isolated was Adenovirus (49%), followed by Bordetella pertussis (41%) from our previous investigation, the most prevelant microorganisms were Mycoplasma pneumonia (26%) and Influenza-B (19.8%). Coinfections were reported in 58% of samples and the most common association was found between B. pertussis and Adenovirus (12.2%). Conclusions: There was a high prevalence of Adenovirus, Mycoplasma pneumoniae and other etiologies in patients with a probable diagnosis of pertussis. Despite the presence of persistent cough lasting at least two weeks and other clinical characteristics highly suspicious of pertussis, secondary etiologies should be considered in children under 5 years-old in order to give a proper treatment. / Revisión por pares

No description available.

The holy grail of structural biology is to study a protein in situ, and this goal has been fast approaching since the resolution revolution and the achievement of atomic resolution. A cell's interior is not a dilute environment, and proteins have evolved to fold and function as needed in that environment; as such, an investigation of a cellular component should ideally include the full complexity of the cellular environment. Imaging whole cells in three dimensions using electron cryotomography is the best method to accomplish this goal, but it comes with a limitation on sample thickness and produces noisy data unamenable to direct analysis. This thesis establishes a novel workflow to systematically analyse whole-cell electron cryotomography data in three dimensions and to find and identify instances of protein complexes in the data to set up a determination of their structure and identity for success. Mycoplasma pneumoniae is a very small parasitic bacterium with fewer than 700 protein-coding genes, is thin enough and small enough to be imaged in large quantities by electron cryotomography, and can grow directly on the grids used for imaging, making it ideal for exploratory studies in structural proteomics. As part of the workflow, a methodology for training deep-learning-based particle-picking models is established. As a proof of principle, a dataset of whole-cell Mycoplasma pneumoniae tomograms is used with this workflow to characterize a novel membrane-associated complex observed in the data. Ultimately, 25431 such particles are picked from 353 tomograms and refined to a density map with a resolution of 11 Å. Making good use of orthogonal datasets to filter search space and verify results, structures were predicted for candidate proteins and checked for suitable fit in the density map. In the end, with this approach, nine proteins were found to be part of the complex, which appears to be associated with chaperone activity and interact with translocon machinery. Visual proteomics refers to the ultimate potential of in situ electron cryotomography: the comprehensive interpretation of tomograms. The workflow presented here is demonstrated to help in reaching that potential. / Der heilige Gral der Strukturbiologie ist die Untersuchung eines Proteins in situ, und dieses Ziel ist seit der Auflösungsrevolution und dem Erreichen der atomaren Auflösung in greifbare Nähe gerückt. Das Innere einer Zelle ist keine verdünnte Umgebung, und Proteine haben sich so entwickelt, dass sie sich falten und so funktionieren, wie es in dieser Umgebung erforderlich ist; daher sollte die Untersuchung einer zellulären Komponente idealerweise die gesamte Komplexität der zellulären Umgebung umfassen. Die Abbildung ganzer Zellen in drei Dimensionen mit Hilfe der Elektronenkryotomographie ist die beste Methode, um dieses Ziel zu erreichen, aber sie ist mit einer Beschränkung der Probendicke verbunden und erzeugt verrauschte Daten, die sich nicht für eine direkte Analyse eignen. In dieser Dissertation wird ein neuartiger Workflow zur systematischen dreidimensionalen Analyse von Ganzzell-Elektronenkryotomographiedaten und zur Auffindung und Identifizierung von Proteinkomplexen in diesen Daten entwickelt, um eine erfolgreiche Bestimmung ihrer Struktur und Identität zu ermöglichen. Mycoplasma pneumoniae ist ein sehr kleines parasitäres Bakterium mit weniger als 700 proteinkodierenden Genen. Es ist dünn und klein genug, um in grossen Mengen durch Elektronenkryotomographie abgebildet zu werden, und kann direkt auf den für die Abbildung verwendeten Gittern wachsen, was es ideal für Sondierungsstudien in der strukturellen Proteomik macht. Als Teil des Workflows wird eine Methodik für das Training von Deep-Learning-basierten Partikelpicken-Modellen entwickelt. Als Proof-of-Principle wird ein Dataset von Ganzzell-Tomogrammen von Mycoplasma pneumoniae mit diesem Workflow verwendet, um einen neuartigen membranassoziierten Komplex zu charakterisieren, der in den Daten beobachtet wurde. Insgesamt wurden 25431 solcher Partikel aus 353 Tomogrammen gepickt und zu einer Dichtekarte mit einer Auflösung von 11 Å verfeinert. Unter Verwendung orthogonaler Datensätze zur Filterung des Suchraums und zur Überprüfung der Ergebnisse wurden Strukturen für Protein-Kandidaten vorhergesagt und auf ihre Eignung für die Dichtekarte überprüft. Letztendlich wurden mit diesem Ansatz neun Proteine als Bestandteile des Komplexes gefunden, der offenbar mit der Chaperonaktivität in Verbindung steht und mit der Translocon-Maschinerie interagiert. Das ultimative Potenzial der In-situ-Elektronenkryotomographie – die umfassende Interpretation von Tomogrammen – wird als visuelle Proteomik bezeichnet. Der hier vorgestellte Workflow soll dabei helfen, dieses Potenzial auszuschöpfen.

Introdução: recente estudo brasileiro detectou a presença concomitante do Mycoplasma pneumoniae e Chlamydia pneumoniae em lesões ateromatosas coronárias estáveis e instáveis. O objetivo do presente estudo foi testar a associação entre títulos sorológicos de anticorpos anti-Chlamydia pneumoniae e anti-Mycoplasma pneumoniae e as Síndromes Isquêmicas Miocárdicas Instáveis. Métodos: foram incluídos de forma prospectiva, 138 pacientes divididos em 4 grupos: 34 pacientes com Síndrome Isquêmica Miocárdica Instável com supradesnível do segmento ST, 40 pacientes com Síndrome Isquêmica Miocárdica Instável sem supradesnível ST, 30 pacientes com aterosclerose crônica assintomática e 34 doadores de sangue sem doença coronária conhecida. Nos dois primeiros grupos, as amostras sorológicas foram colhidas durante o evento agudo e com seis meses de seguimento, enquanto nos outros dois (aterosclerose crônica e controle) as mesmas foram colhidas uma única vez. Em todas as amostras foram dosados anticorpos da classe IgG anti-Chlamydia pneumoniae e anti-Mycoplasma pneumoniae utilizando a técnica de imunoflorescência indireta.. Resultados: seis meses após a internação, os pacientes com síndrome isquêmica miocárdica instável com supradesnível ST apresentaram significativa redução dos títulos sorológicos, em relação às sorologias colhidas durante o evento coronário agudo, o que ocorreu tanto com a chlamydia (307,5+47,5 versus 650+115,7 p=0,0001) quanto com o mycoplasma (21,5+3,5 versus 36,5+5 p=0,0004). O grupo sem supradesnível ST não teve variação significativa dos níveis sorológicos em seis meses de seguimento (522,6+102,7 versus 576+84,1 p=0,27) para chlamydia e 27,6+5,8 versus 27,6 + 5,8 p >0,99 para mycoplasma. Foi realizada também uma comparação entre os níveis sorológicos de todos os grupos analisados, e observou-se que os grupos com síndrome isquêmica miocárdica instável (com e sem supra ST), tiveram valores sorológicos mais elevados do que os grupos aterosclerose crônica e controle, mas as diferenças não foram significativas. Os valores para chlamydia foram: 650+115,7 (com supra), 576+84 (sem supra), 373,3+65 (aterosclerose crônica) e 343,5+57,2 (controle), p=0,083; e os valores para mycoplasma foram: 36,5+5 (com supra), 27,6+5,8 (sem supra), 23+4,3 (aterosclerose crônica) e 26,7+3,3 (controle), p=0,171. Conclusões: o presente estudo demonstra associação entre títulos de anticorpos anti-Chlamydia pneumoniae e anti-Mycoplasma pneumoniae e a instabilização da placa coronária. Demonstra ainda a normalização dos mesmos títulos em um período de até seis meses, a partir do quadro agudo. / Objective of the study: to test the association of serum titers of anti-Chlamydia pneumoniae and anti-Mycoplasma pneumoniae antibodies and Acute Coronary Syndrome (ACS). The patients were divided into 4 groups: ACS with ST-segment elevation, ACS without ST-segment elevation, chronic asymptomatic atherosclerosis and blood donors without known coronary disease. Serum samples were collected during the acute event and after six months of follow-up. Six months after the acute event, patients with ACS with St-segment elevation showed a significant decrease of serum titers, when compared to the other one. That\'s show the association between anti-Chlamydia pneumoniae and anti-Mycoplasma pneumoniae antibody titers and acute coronary syndrome.

Introdução: recente estudo brasileiro detectou a presença concomitante do Mycoplasma pneumoniae e Chlamydia pneumoniae em lesões ateromatosas coronárias estáveis e instáveis. O objetivo do presente estudo foi testar a associação entre títulos sorológicos de anticorpos anti-Chlamydia pneumoniae e anti-Mycoplasma pneumoniae e as Síndromes Isquêmicas Miocárdicas Instáveis. Métodos: foram incluídos de forma prospectiva, 138 pacientes divididos em 4 grupos: 34 pacientes com Síndrome Isquêmica Miocárdica Instável com supradesnível do segmento ST, 40 pacientes com Síndrome Isquêmica Miocárdica Instável sem supradesnível ST, 30 pacientes com aterosclerose crônica assintomática e 34 doadores de sangue sem doença coronária conhecida. Nos dois primeiros grupos, as amostras sorológicas foram colhidas durante o evento agudo e com seis meses de seguimento, enquanto nos outros dois (aterosclerose crônica e controle) as mesmas foram colhidas uma única vez. Em todas as amostras foram dosados anticorpos da classe IgG anti-Chlamydia pneumoniae e anti-Mycoplasma pneumoniae utilizando a técnica de imunoflorescência indireta.. Resultados: seis meses após a internação, os pacientes com síndrome isquêmica miocárdica instável com supradesnível ST apresentaram significativa redução dos títulos sorológicos, em relação às sorologias colhidas durante o evento coronário agudo, o que ocorreu tanto com a chlamydia (307,5+47,5 versus 650+115,7 p=0,0001) quanto com o mycoplasma (21,5+3,5 versus 36,5+5 p=0,0004). O grupo sem supradesnível ST não teve variação significativa dos níveis sorológicos em seis meses de seguimento (522,6+102,7 versus 576+84,1 p=0,27) para chlamydia e 27,6+5,8 versus 27,6 + 5,8 p >0,99 para mycoplasma. Foi realizada também uma comparação entre os níveis sorológicos de todos os grupos analisados, e observou-se que os grupos com síndrome isquêmica miocárdica instável (com e sem supra ST), tiveram valores sorológicos mais elevados do que os grupos aterosclerose crônica e controle, mas as diferenças não foram significativas. Os valores para chlamydia foram: 650+115,7 (com supra), 576+84 (sem supra), 373,3+65 (aterosclerose crônica) e 343,5+57,2 (controle), p=0,083; e os valores para mycoplasma foram: 36,5+5 (com supra), 27,6+5,8 (sem supra), 23+4,3 (aterosclerose crônica) e 26,7+3,3 (controle), p=0,171. Conclusões: o presente estudo demonstra associação entre títulos de anticorpos anti-Chlamydia pneumoniae e anti-Mycoplasma pneumoniae e a instabilização da placa coronária. Demonstra ainda a normalização dos mesmos títulos em um período de até seis meses, a partir do quadro agudo. / Objective of the study: to test the association of serum titers of anti-Chlamydia pneumoniae and anti-Mycoplasma pneumoniae antibodies and Acute Coronary Syndrome (ACS). The patients were divided into 4 groups: ACS with ST-segment elevation, ACS without ST-segment elevation, chronic asymptomatic atherosclerosis and blood donors without known coronary disease. Serum samples were collected during the acute event and after six months of follow-up. Six months after the acute event, patients with ACS with St-segment elevation showed a significant decrease of serum titers, when compared to the other one. That\'s show the association between anti-Chlamydia pneumoniae and anti-Mycoplasma pneumoniae antibody titers and acute coronary syndrome.

Un des objectifs de la biologie de synthèse est de concevoir et produire des organismes « à façon », pour des applications thérapeutiques et industrielles. Une des voies envisagées pour atteindre cet objectif repose sur des techniques de synthèse et de transplantation de génomes entiers, afin de créer des organismes mutants.Le but de cette thèse est de développer des outils de biologie de synthèse qui permettront de construire une cellule minimale et non pathogène, à partir de Mycoplasma pneumoniae. Cette bactérie est l'un des plus petits organismes vivants, avec une taille inférieure au micron et un génome de 816 kpb. Ce mycoplasme est l’un des plus étudiés, avec une collection de données génétiques et multi-« omiques » disponibles. Ces caractéristiques font de cette cellule naturellement « quasi minimale » un point de départ idéal pour la construction d’un châssis bactérien. Néanmoins, la manipulation génétique de ce mycoplasme est difficile, en raison du nombre restreint d'outils disponibles.Une approche récemment développée propose de contourner ces limitations en utilisant la levure Saccharomyces cerevisiae comme plateforme d’ingénierie du génome de M. pneumoniae. L’étape préliminaire à cette approche consiste à cloner le génome bactérien dans la levure. Pour ce faire, une cassette « éléments levure » est insérée dans le génome de M. pneumoniae, pour permettre son maintien comme chromosome artificiel. Les travaux menés au cours de cette thèse ont permis d’insérer cette cassette par le biais d’un transposon, et de cloner ce génome marqué dans la levure. La stabilité du génome cloné a ensuite été étudiée, mettant en évidence que le chromosome bactérien est maintenu durant une dizaine de passages. Nous avons ensuite développé une nouvelle stratégie d’insertion des « éléments levure » en utilisant le système CRISPR/Cas9 pour cloner et éditer simultanément un génome de mycoplasme chez la levure : le CReasPy-Cloning. Cette méthode a été utilisée pour supprimer trois loci différents contenant des gènes impliqués dans la virulence : MPN372 (toxine CARDS), MPN142 (protéine de cytoadhérence) et MPN400 (protéine bloquant les IgG). Elle a ensuite été utilisée pour en cibler deux puis trois en une seule étape.Une fois le clonage et l’ingénierie du génome bactérien réalisés dans la levure, il est nécessaire de pouvoir transférer le chromosome modifié dans une cellule receveuse, afin de produire une cellule mutante. Ce processus nommé transplantation de génome n’étant pas décrit pour M. pneumoniae, une part importante de cette thèse a été dédiée au développement de cet outil. Nous avons utilisé la transformation de plasmides comme mécanisme modèle pour étudier le processus d’entrée de l’ADN dans M. pneumoniae et tester l’utilisation du polyéthylène glycol, le réactif clé de la transplantation. Bien qu’ayant réussi à mettre au point un protocole de transformation de plasmides, nous n’avons pas réussi pour l’instant à réaliser la transplantation de génomes.En parallèle, nous avons développé une stratégie alternative d’édition de génome qui ne dépend pas de la transplantation. Cette approche, nommée « Genomic Transfer - Recombinase-Mediated Cassette Exchange » (GT-RMCE), consiste à capturer dans un vecteur une section du génome bactérien édité présent dans la levure. Ce vecteur est transformé dans M. pneumoniae, et grâce au système Cre-lox la section éditée est introduite dans le génome. Ce mécanisme permet de réaliser des modifications de grande ampleur, et est actuellement utilisé pour introduire chez M. pneumoniae les délétions ΔMPN372, ΔMPN400 et ΔMPN372-ΔMPN400 produites par CReasPy-cloning. Nous avons également utilisé le GT-RMCE pour générer une souche de M. pneumoniae portant deux copies de l’opéron ribosomal S10.Au final, les outils d’ingénierie du génome de M. pneumoniae développés au cours de cette thèse permettent de réaliser un pas significatif vers la construction de nouveaux châssis bactériens. / A goal of synthetic biology is to create and produce “custom” organisms, for therapeutic and industrial applications. One of the contemplated approaches to achieve this goal is based on synthesis techniques and transplantation of whole genomes, in order to create mutant organisms.The aim of this thesis is to develop synthetic biology tools that will enable the construction of a minimal and non-pathogenic cell based on Mycoplasma pneumoniae. This bacterium is one of the smallest living organisms, with a size smaller than one micron and a genome of 816 kbp. This mycoplasma is one of the most studied, with a large set of genetic and multi- “omics” data available. These characteristics make this naturally “almost minimal” cell an ideal starting point for the construction of a bacterial chassis. Nevertheless, the genetic manipulation of this mycoplasma is difficult, due to the limited number of available tools.A recently developed approach offers the possibility to circumvent these limitations by using the yeast Saccharomyces cerevisiae as a genome engineering platform for M. pneumoniae. The preliminary step to this strategy is to clone the bacterial genome in yeast. To do so, a "yeast elements" cassette is inserted into the genome of M. pneumoniae, to allow its maintenance as an artificial chromosome. The work carried out during this thesis allowed us to insert this cassette through a transposon, and to clone this marked genome in yeast. Then, the stability of the cloned genome was studied, demonstrating that the bacterial chromosome is maintained during ten passages. We then developed a new strategy for the insertion of the "yeast elements", using the CRISPR/Cas9 system to simultaneously clone and edit a mycoplasma genome in yeast: the CReasPy-Cloning. This method was used to remove three different loci containing genes involved in virulence: MPN372 (CARDS toxin), MPN142 (cytoadherence protein) and MPN400 (IgG blocking protein). This method was also used to target two and then three different loci in one step.Once in-yeast cloning and bacterial genome engineering is achieved, it is necessary to transfer the modified chromosome into a recipient cell, to produce a mutant organism. This process, called genome transplantation, is not described for M. pneumoniae, so a significant part of this thesis was dedicated to the development of this tool. We used plasmid transformation as a model mechanism to study the process of DNA entry into M. pneumoniae and to test the use of polyethylene glycol, the key reagent for transplantation. Although we succeeded in developing a plasmid transformation protocol, we have not yet been able to perform genome transplantation.Concurrently, we have developed an alternative strategy for genome editing that does not depend on transplantation. This approach, named "Genomic Transfer - Recombinase-Mediated Cassette Exchange" (GT-RMCE), is used to capture in a vector a section of the edited bacterial genome borne by the yeast. This vector is then transformed into M. pneumoniae, and through to the Cre-lox system the edited section is introduced into the genome. This mechanism allows to carry out large-scale modifications, and is currently used to introduce into M. pneumoniae the ΔMPN372, ΔMPN400 and ΔMPN372-ΔMPN400 deletions produced by CReasPy-cloning. We also used the GT-RMCE to generate a strain of M. pneumoniae carrying two copies of the S10 ribosomal operon.Overall, the M. pneumoniae genome engineering tools developed during this thesis constitute a significant step towards the construction of new bacterial chassis.

Mycoplasma pneumoniae, einer der kleinsten lebenden Organismen, ist ein erfolgversprechender Modellorganismus der Systembiologie um eine komplette lebende Zelle zu verstehen. Wichtig dahingehend ist die Konstruktion mathematischer Modelle, die zelluläre Prozesse beschreiben, indem sie beteiligte Komponenten vernetzen und zugrundeliegende Mechanismen entschlüsseln. Für Mycoplasma pneumoniae wurden genomweite Datensätze für Genomics, Transcriptomics, Proteomics und Metabolomics produziert. Allerdings fehlten ein effizientes Informationsaustauschsystem und mathematische Modelle zur Datenintegration. Zudem waren verschiedene Beobachtungen im metabolischen Verhalten ungeklärt. Diese Dissertation präsentiert einen kombinatorischen Ansatz zur Entwicklung eines metabolischen Modells für Mycoplasma pneumoniae. Zuerst haben wir eine Datenbank, MyMpn, entwickelt, um Zugang zu strukturierten, organisierten Daten zu schaffen. Danach haben wir ein genomweites, Constraint-basiertes metabolisches Modell mit Vorhersagekapazitäten konstruiert und parallel dazu das Metabolome experimentell charakterisiert. Wir haben die Biomasse einer Mycoplasma pneumoniae Zelle definiert, das Netzwerk korrigiert, gezeigt, dass ein Grossteil der produzierten Energie auf zelluläre Homeostase verwendet wird, und das Verhalten unter verschiedenen Wachstumsbedingungen analysiert. Schließlich haben wir manuell das Genom reannotiert. Die Datenbank, obwohl noch nicht öffentlich zugänglich, wird bereits intern für die Analyse experimenteller Daten und die Modellierung genutzt. Die Entdeckung von Kontrollprinzipien des Energiemetabolismus und der Anpassungsfähigkeiten bei Genausfall heben den Einfluss der reduktiven Genomevolution hervor und erleichtert die Entwicklung von Manipulationstechniken und dynamischen Modellen. Überdies haben wir gezeigt, dass die Genomorganisation in Mycoplasma pneumoniae komplexer ist als bisher für möglich gehalten, und 32 neue, noch nicht annotierte Gene entdeckt. / Mycoplasma pneumoniae, one of the smallest known self-replicating organisms, is a promising model organism in systems biology when aiming to assess understanding of an entire living cell. One key step towards this goal is the design of mathematical models that describe cellular processes by connecting the involved components to unravel underlying mechanisms. For Mycoplasma pneumoniae, a wealth of genome-wide datasets on genomics, transcriptomics, proteomics, and metabolism had been produced. However, a proper system facilitating information exchange and mathematical models to integrate the different datasets were lacking. Also, different in vivo observations of metabolic behavior remained unexplained. This thesis presents a combinatorial approach to design a metabolic model for Mycoplasma pneumoniae. First, we developed a database, MyMpn, in order to provide access to structured and organized data. Second, we built a predictive, genome-scale, constraint-based metabolic model and, in parallel, we explored the metabolome in vivo. We defined the biomass composition of a Mycoplasma pneumoniae cell, corrected the wiring diagram, showed that a large proportion of energy is dedicated to cellular homeostasis, and analyzed the metabolic behavior under different growth conditions. Finally, we manually re-annotated the genome of Mycoplasma pneumoniae. The database, despite not yet being released to the public, is internally already used for data analysis, and for mathematical modeling. Unraveling the principles governing energy metabolism and adaptive capabilities upon gene deletion highlight the impact of the reductive genome evolution and facilitates the development of engineering tools and dynamic models for metabolic sub-systems. Furthermore, we revealed that the degree of complexity in which the genome of Mycoplasma pneumoniae is organized far exceeds what has been considered possible so far and we identified 32 new, previously not annotated genes.

Background: Persistent cough following an acute respiratory tract infection is a challenging and frequently encountered problem in primary care. Mycoplasma pneumoniae (M. pneumoniae) and Bordetella pertussis (pertussis) particularly predispose patients to persistent cough. Whilst the incidence of M. pneumoniae is highest in children, pertussis may also occur in adults. Method: Four studies were conducted for this thesis. First, a systematic review to assess the diagnostic accuracy of symptoms and signs in the clinical recognition of M. pneumoniae. Second, a retrospective analysis of a cohort of children with persistent cough to assess the prognostic value of diagnosing M. pneumoniae. Third, a prospective cohort study to estimate the prevalence of M. pneumoniae and pertussis in children with persistent cough following recent changes in vaccination policy. Fourth, a double-blind randomised placebo-controlled trial to determine the effectiveness of montelukast in the treatment of persistent cough and pertussis-induced cough in adults. Results: M. pneumoniae and pertussis can each be found in one-sixth of children who present in primary care with persistent cough. Although coverage with the preschool pertussis booster vaccine is high, its efficacy wanes rapidly, with the likelihood of pertussis increasing by 30% per year after vaccination. Montelukast is not an effective treatment for persistent cough, but may be an effective treatment for pertussis-induced cough. Median duration of cough in children with M. pneumoniae is only one-third of that in children with pertussis (39 days versus 118 days). However, the diagnostic accuracy of symptoms and signs in the clinical recognition of M. pneumoniae is limited. Since M. pneumoniae occurs in cyclical epidemics, clinicians should consider current prevalence of M. pneumoniae when making a clinical diagnosis. Conclusions: Diagnosing M. pneumoniae and pertussis can help clinicians give patients an explanation for their cough and inform them about its likely prognosis. At the moment, clinicians should adopt a conservative approach to managing postinfectious persistent cough. A further trial is needed to assess the efficacy of montelukast for the treatment of pertussis-induced cough.

Background Mycoplasma pneumoniae and Chlamydia pneumoniae are atypical pathogens responsible for pneumonia and a leading cause of morbidity and mortality in low income countries. The study objective is to determine the prevalence of this pathogens in Peruvian children with acute respiratory infections. Methods A consecutive cross-sectional study was conducted in Lima, Peru from May 2009 to September 2010. A total of 675 children admitted with clinical diagnoses of acute respiratory infections were tested for Mycoplasma pneumoniae and Chlamydia pneumoniae detection by polymerase chain reaction (PCR), and clinical symptoms were registered by the attending physician. Results Mycoplasma pneumonia was detected in 25.19% (170/675) of nasopharyngeal samples and Chlamydia pneumonia in 10.52% (71/675). The most common symptoms in patients with these atypical pathogens were rhinorrhea, cough and fever. A higher prevalence of Mycoplasma pneumoniae cases were registered in summer, between December 2009 and March 2010. Conclusions Mycoplasma pneumoniae and Chlamydia pneumonia are a significant cause of morbidity in Peruvian children with acute respiratory infections (ARI). Further studies should evaluate the use of reliable techniques such as PCR in Peru in order to avoid underdiagnoses of these atypical pathogens.