Diagnostic interest of whole-body MRI in early- and late-onset LAMA2 muscular dystrophies: a large international cohort.

BACKGROUND: LAMA2-related muscular dystrophy (LAMA2-RD) encompasses a group of recessive muscular dystrophies caused by mutations in the LAMA2 gene, which codes for the alpha-2 chain of laminin-211 (merosin). Diagnosis is straightforward in the classic congenital presentation with no ambulation and complete merosin deficiency in muscle biopsy, but is far more difficult in milder ambulant individuals with partial merosin deficiency. OBJECTIVE: To investigate the diagnostic utility of muscle imaging in LAMA2-RD using whole-body magnetic resonance imaging (WBMRI). RESULTS: 27 patients (2-62 years, 21-80% with acquisition of walking ability and 6 never ambulant) were included in an international collaborative study. All carried two pathogenic mutations, mostly private missense changes. An intronic variant (c.909 + 7A > G) was identified in all the Chilean cases. Three patients (two ambulant) showed intellectual disability, epilepsy, and brain structural abnormalities. WBMRI T1w sequences or T2 fat-saturated images (Dixon) revealed abnormal muscle fat replacement predominantly in subscapularis, lumbar paraspinals, gluteus minimus and medius, posterior thigh (adductor magnus, biceps femoris, hamstrings) and soleus. This involvement pattern was consistent for both ambulant and non-ambulant patients. The degree of replacement was predominantly correlated to the disease duration, rather than to the onset or the clinical severity. A "COL6-like sandwich sign" was observed in several muscles in ambulant adults, but different involvement of subscapularis, gluteus minimus, and medius changes allowed distinguishing LAMA2-RD from collagenopathies. The thigh muscles seem to be the best ones to assess disease progression. CONCLUSION: WBMRI in LAMA2-RD shows a homogeneous pattern of brain and muscle imaging, representing a supportive diagnostic tool.

Recomendaciones para el diagnóstico y manejo de la infección por citomegalovirus en la mujer embarazada y el recién nacido / Recommendations for the diagnosis and management of cytomegalovirus infection in pregnant woman and newborn infant

Resumen La Sociedad Chilena de Infectología, a través de su Comité de Infecciones Neonatales, en conjunto con la Sociedad Chilena de Obstetricia y Ginecología, proponen un documento de diagnóstico y manejo de la Infección por Citomegalovirus en la Mujer Embarazada y el Recién Nacido. Esta guía aborda el manejo de la infección en el binomio, su enfrentamiento diagnóstico y terapéutico, orientado al equipo de salud que atiende a mujeres embarazadas y recién nacidos con infección por citomegalovirus (CMV) en Chile. Considera la situación epidemiológica global y latinoamericana, con recomendaciones para la evaluación clínica y de laboratorio; establece criterios de diagnóstico, propone enfoques terapéuticos de acuerdo a la situación clínica, analiza las medidas de prevención y establece una propuesta nacional para el seguimiento de esta enfermedad. Se ha puesto especial énfasis en entregar, de forma práctica, y con la mayor evidencia posible, las recomendaciones para el manejo del binomio con infección por CMV.

Abstract The Chilean Society of Infectology, through its Neonatal Infections Committee in conjunction with the Chilean Society of Obstetrics and Gynecology, propose a document for the Diagnosis and Management of Cytomegalovirus Infection in Pregnant Woman and Newborn Infant. This guideline suggests the management of mother and child infection, its diagnostic and therapeutic options. Considers the global and Latin American epidemiology, with recommendations for clinical and laboratory evaluation; diagnostic criteria, therapeutic approaches according to the clinical situation, analyzes prevention measures and establishes a national proposal for monitoring this disease.

Recomendaciones para el diagnóstico y el manejo de la infección por citomegalovirus en la mujer embarazada y el recién nacido / Recommendations for the diagnosis and management of cytomegalovirus infection in pregnant women and newborns

Resumen La Sociedad Chilena de Infectología, a través de su Comité de Infecciones Neonatales, en conjunto con la Sociedad Chilena de Obstetricia y Ginecología, proponen un documento de diagnóstico y manejo de la infección por citomegalovirus (CMV) en la mujer embarazada y el recién nacido. Esta guía aborda el manejo de la infección en el binomio, su enfrentamiento diagnóstico y terapéutico, orientado al equipo de salud que atiende a mujeres embarazadas y recién nacidos con infección por CMV en Chile. Considera la situación epidemiológica global y latinoamericana, con recomendaciones para la evaluación clínica y de laboratorio; establece criterios de diagnóstico, propone enfoques terapéuticos de acuerdo a la situación clínica, analiza las medidas de prevención y establece una propuesta nacional para el seguimiento de esta enfermedad. Se ha puesto especial énfasis en entregar, de forma práctica, y con la mayor evidencia posible, las recomendaciones para el manejo del binomio con infección por CMV.

Abstract The Chilean Society of Infectology, through its Neonatal Infections Committee in conjunction with the Chilean Society of Obstetrics and Gynecology, propose a document for the Diagnosis and Management of Cytomegalovirus Infection in Pregnancy and Newborn. This guideline suggests the management of mother and child infection, its diagnostic and therapeutic options. Considers the global and Latin American epidemiology, with recommendations for clinical and laboratory evaluation, diagnostic criteria, therapeutic approaches according to the clinical situation, analyzes prevention measures and establishes a national proposal for monitoring this disease.

Spontaneous symptomatic improvement in a pediatric patient with anti-3-hydroxy-3-methylglutraryl-coenzyme A reductase myopathy.

Immune-mediated necrotizing myopathy with antibodies against 3-hydroxy-3-methylglutaryl-coenzyme A reductase is a subgroup of idiopathic inflammatory myopathies mainly described in adults and requiring long term immunomodulatory therapy for remission. Pediatric patients have been reported as small series or sporadic cases. We report an eight-year-old girl with anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase myopathy, presenting with subacute proximal limb weakness, high creatine kinase and a muscle biopsy displaying necrotizing pattern, initially diagnosed as limb-girdle muscular dystrophy, but subsequently negative genetic testing. A noteworthy spontaneous improvement in her weakness suggested the possibility of an acquired autoimmune myopathy, confirmed by positive testing of anti-HMGCR antibodies titers. After four years of follow-up, she maintains normal strength with high levels of anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase antibody. This patient shows that spontaneous fluctuations and spontaneous long-lasting symptomatic remission can occur in patients with anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase myopathy. Some patients could present a wane and wax clinical course, an important aspect when assessing response to therapy.

A general protein O-glycosylation machinery conserved in Burkholderia species improves bacterial fitness and elicits glycan immunogenicity in humans.

The Burkholderia genus encompasses many Gram-negative bacteria living in the rhizosphere. Some Burkholderia species can cause life-threatening human infections, highlighting the need for clinical interventions targeting specific lipopolysaccharide proteins. Burkholderia cenocepacia O-linked protein glycosylation has been reported, but the chemical structure of the O-glycan and the machinery required for its biosynthesis are unknown and could reveal potential therapeutic targets. Here, using bioinformatics approaches, gene-knockout mutants, purified recombinant proteins, LC-MS-based analyses of O-glycans, and NMR-based structural analyses, we identified a B. cenocepacia O-glycosylation (ogc) gene cluster necessary for synthesis, assembly, and membrane translocation of a lipid-linked O-glycan, as well as its structure, which consists of a ß-Gal-(1,3)-α-GalNAc-(1,3)-ß-GalNAc trisaccharide. We demonstrate that the ogc cluster is conserved in the Burkholderia genus, and we confirm the production of glycoproteins with similar glycans in the Burkholderia species: B. thailandensis, B. gladioli, and B. pseudomallei Furthermore, we show that absence of protein O-glycosylation severely affects bacterial fitness and accelerates bacterial clearance in a Galleria mellonella larva infection model. Finally, our experiments revealed that patients infected with B. cenocepacia, Burkholderia multivorans, B. pseudomallei, or Burkholderia mallei develop O-glycan-specific antibodies. Together, these results highlight the importance of general protein O-glycosylation in the biology of the Burkholderia genus and its potential as a target for inhibition or immunotherapy approaches to control Burkholderia infections.

[Collagen VI related myopathies. When to suspect, how to identify. The contribution of muscle magnetic resonance]. / Miopatías relacionadas a colágeno VI. Cuando sospecharlas, cómo identificarlas. Aporte de la resonancia magnética muscular.

Myopathies secondary to collagen VI mutations (COLVI-M) are the most frequent in the northern hemisphere, affecting the adult and pediatric population. There are no data on its prevalence in Latin America. They are characterized by a great clinical variability, from severe phenotypes, such as Ullrich congenital muscular dystrophy (UCMD), to intermediate and mild ones such as Bethlem myopathy (BM). Its onset is also variable and extends from the neonatal period to adulthood. Given the presence of joint hypermobility, the differential diagnosis should be made with various connective tissue diseases. The classical diagnostic algorithm in many patients has been insufficient to guide the genetic study in an adequate way, and from this the muscular magnetic resonance imaging has emerged as a very useful tool for a better diagnostic approach of this and other muscular pathologies. This ob jective of this review is to study the forms of presentation, clinical characteristics, specific diagnostic study, differential diagnosis and management of one of the most frequent hereditary muscular patho logies, with emphasis on the contribution of muscle magnetic resonance imaging.

Miopatías relacionadas a colágeno VI: cuando sospecharlas, cómo identificarlas: aporte de la resonancia magnética muscular / Collagen VI related myopathies: when to suspect, how to identify: the contribution of muscle magnetic resonance

Resumen: Las miopatías secundarias a mutaciones en el colágeno VI (M-COLVI) son las más frecuentes en el hemisferio norte, afectando población adulta y pediátrica. No existen datos de su prevalencia en Latinoamérica. Se caracterizan por presentar una gran variabilidad clínica, desde fenotipos severos, como la distrofia muscular congénita de Ullrich (DMCU), a intermedios y leves como la Miopatía de Bethlem (MB). Su inicio también es variable y se extiende desde el período de recién nacido hasta la vida adulta. Dada la presencia de hiperlaxitud articular, el diagnóstico diferencial se debe realizar con diversas enfermedades del tejido conectivo. El algoritmo diagnóstico clásico en muchos pacientes ha sido insuficiente para orientar el estudio genético de forma adecuada, y a partir de esto la resonancia magnética muscular ha emergido como una herramienta de gran utilidad para una mejor aproxima ción diagnóstica de ésta y otras patologías musculares. Esta revisión tiene como objetivo examinar las formas de presentación, características clínicas, estudio diagnóstico específico, diagnóstico dife rencial y manejo de una de las patologías musculares herediatarias más frecuentes, con énfasis en el aporte de la resonancia magnética muscular.

Abstract: Myopathies secondary to collagen VI mutations (COLVI-M) are the most frequent in the northern hemisphere, affecting the adult and pediatric population. There are no data on its prevalence in Latin America. They are characterized by a great clinical variability, from severe phenotypes, such as Ullrich congenital muscular dystrophy (UCMD), to intermediate and mild ones such as Bethlem myopathy (BM). Its onset is also variable and extends from the neonatal period to adulthood. Given the presence of joint hypermobility, the differential diagnosis should be made with various connective tissue diseases. The classical diagnostic algorithm in many patients has been insufficient to guide the genetic study in an adequate way, and from this the muscular magnetic resonance imaging has emerged as a very useful tool for a better diagnostic approach of this and other muscular pathologies. This ob jective of this review is to study the forms of presentation, clinical characteristics, specific diagnostic study, differential diagnosis and management of one of the most frequent hereditary muscular patho logies, with emphasis on the contribution of muscle magnetic resonance imaging.

Insights from genotype-phenotype correlations by novel SPEG mutations causing centronuclear myopathy.

Centronuclear myopathies (CNM) are a clinically and genetically heterogeneous group of congenital myopathies, defined histologically by increased number of fibres with centrally located nuclei, and type I fibre predominance in muscle biopsy. Myotubular myopathy, the X-linked form of CNM caused by mutations in the phosphoinositide phosphatase MTM1, is histologically characteristic since muscle fibres resemble myotubes. Here we present two unrelated patients with CNM and typical myotubular fibres in the muscle biopsy caused by mutations in striated muscle preferentially expressed protein kinase (SPEG). Next generation sequencing revealed novel biallelic homozygous mutations in SPEG in both cases. Patient 1 showed the c.1627_1628insA (p.Thr544Aspfs*48) mutation and patient 2 the c.9586C>T (p.Arg3196*) mutation. The clinical phenotype was distinctive in the two patients since patient 2 developed a dilated cardiomyopathy with milder myopathy features, while patient 1 showed only myopathic features without cardiac involvement. These findings expand the genotype-phenotype correlations after the initial report. Additionally, we describe whole body muscle MRI of patient 2 and we argue on the different SPEG isoforms in skeletal muscle and heart as the possible explanation leading to variable phenotypes of SPEG mutations.

The LpxL acyltransferase is required for normal growth and penta-acylation of lipid A in Burkholderia cenocepacia.

Lipid A anchors the lipopolysaccharide (LPS) to the outer membrane and is usually composed of a hexa-acylated diglucosamine backbone. Burkholderia cenocepacia, an opportunistic pathogen, produces a mixture of tetra- and penta-acylated lipid A. "Late" acyltransferases add secondary acyl chains to lipid A after the incorporation of four primary acyl chains to the diglucosamine backbone. Here, we report that B. cenocepacia has only one late acyltransferase, LpxL (BCAL0508), which adds a myristoyl chain to the 2' position of lipid A resulting in penta-acylated lipid A. We also identified PagL (BCAL0788), which acts as an outer membrane lipase by removing the primary ß-hydroxymyristate (3-OH-C14:0) chain at the 3 position, leading to tetra-acylated lipid A. Unlike PagL, LpxL depletion caused reduced cell growth and defects in cell morphology, both of which were suppressed by overexpressing the LPS flippase MsbA (BCAL2408), suggesting that lipid A molecules lacking the fifth acyl chain contributed by LpxL are not good substrates for the flippase. We also show that intracellular B. cenocepacia within macrophages produced more penta-acylated lipid A, suggesting lipid A penta-acylation in B. cenocepacia is required not only for bacterial growth and morphology but also for adaptation to intracellular lifestyle.

Resonancia magnética fetal en el estudio prequirúrgico de disrafia espinal / Foetal magnetic resonance imaging in the pre-surgical assessment of spinal dysraphism

Abstract. Spinal dysraphism is an important indication for foetal magnetic resonance imaging (MRI), considering the evaluation of potential candidates for intrauterine surgery. Foetal MRI has proved to be superior to 2D and 3D ultrasound for the posterior fossa, brain stem, corpus callosum, and cortical development abnormalities. The description and level of spinal injury, hydrocephalus, magnitude of cerebellum herniation, and associated injuries, are valuable information, which is useful for the preoperative assessment, as well as for the comparison with postnatal studies.

Resumen. Las disrafias espinales son una indicación importante de resonancia magnética fetal (RMF), considerando la evaluación de posibles candidatos para cirugía intrauterina. La RMF ha demostrado ser superior a la ultrasonografía 3D y 2D para la evaluación de la fosa posterior, el tronco cerebral, el cuerpo calloso, y las anormalidades del desarrollo de la corteza cerebral. La descripción y el nivel del daño espinal, el grado de hidrocefalia, la magnitud de la herniación del cerebelo, y la presencia de lesiones asociadas son variables importantes, útiles para la planificación preoperatoria y la comparación con estudios posnatales.

Variabilidad en la determinación de fracción grasa muscular en resonancia magnética utilizando la técnica de Dixon / Variability in magnetic resonance quantification of muscle fat fraction using Dixon's technique

Abstract. Muscle MRI has emerged as a valuable tool in the diagnosis of neuromuscular-disorders. The Dixon fat-water separation technique allows objective intra-muscular fat quantification. There are few reports concerning measurement standardisation with Dixon technique. The objective of this study was to evaluate the variability in fat quantification using Dixon's technique in a cohort of patients with congenital myopathies, by analysing intra-segment, intra-muscle, and inter-muscle variability of 60 muscles in each patient. Whole body MRI was performed on 31 patients, 23 with congenital myopathies and 8 healthy controls, aged between 10 months and 35 years old, from January 2014 to June 2016. The mean fat-fraction in healthy patients was around 5%, with less than 2% intra-muscle variability. An intra-muscle variability between 3.1-7.8% was estimated in patients with congenital myopathies. It may be concluded that there is high intra- and inter-muscle fat-fraction variability among patients with congenital myopathies, and this is an observation that should be incorporated in the analysis of fat replacement.

Resumen. La resonancia magnética muscular ha emergido como una valiosa herramienta de apoyo diagnóstico en enfermedades neuromusculares. La técnica de Dixon permite objetivar la fracción grasa muscular, pero no existe consenso sobre la estandarización de estas mediciones. El objetivo de este estudio fue evaluar la variabilidad en la determinación de fracción grasa utilizando la técnica de Dixon, estudiando la variabilidad intrasegmentaria, intramuscular e intermuscular en 60 músculos por paciente. Se realizó RM de cuerpo completo a 31 pacientes: 23 con miopatía congénita y 8 controles, entre 10 meses y 35 años de edad, desde enero del 2014 a junio del 2016. En pacientes sanos se estimó una fracción grasa promedio cercana al 5%, con una variabilidad intramuscular inferior al 2%. En pacientes con miopatías congénitas existe una variabilidad entre el 3,1-7,8%. El estudio permite concluir que existe una alta variabilidad intra e intermuscular en pacientes miopáticos, que no se observa en pacientes sanos.

Diagnóstico prenatal y manejo perinatal en enfermedades raras / Prenatal diagnosis and management of rare diseases

El diagnóstico y manejo prenatal de enfermedades raras involucra un estudio multidisciplinario. Desde una visión obstétrica, herramientas de imagenología como la ultrasonografía y en menor medida la resonancia magnética fetal (RMF) son esenciales para el diagnóstico de anomalías morfológicas y sospecha de defectos cromosómicos. Para el diagnóstico de enfermedades cromosómicas el estudio de cariograma obtenido de vellosidades coriales, líquido amniótico o sangre fetal mediante técnicas invasivas tal como biopsia corial, amniocentesis o cordocentesis ha sido hasta hace poco el gold standard del diagnóstico. Nuevas técnicas moleculares capaces de detectar microdeleciones como es el microarray nos ha permitido aproximarnos al origen de las enfermedades raras. Se revisarán además algunos de los defectos anatómicos raros y su enfoque neonatal.

Prenatal diagnosis and management of rare diseases is a multidisciplinary task. From the obstetric vision, prenatal diagnosis is based on fetal images obtained by ultrasound or magnetic resonance and fetal chromosomes study. The study of fetal morphology allows us the diagnosis of fetal abnormalities and the suspicion of chromosomal defects. Fetal chromosomal study is obtained either by chorionic villus sampling, amniocentesis and cordocentesis, all associated to fetal risk. New screening techniques such as fetal DNA on maternal blood or the study of fetal micro deletions using micro Array on amniotic fluid has extended diagnostic opportunity of rare fetal diseases. We will review some of the most common rare diseases and the neonatal approach.

Chemical and botanical characterization of Chilean propolis and biological activity on cariogenic bacteria Streptococcus mutans and Streptococcus sobrinus.

Propolis is a non-toxic natural substance with multiple pharmacological properties including anti-cancer, antioxidant, fungicidal, antibacterial, antiviral, and anti-inflammatory among others. The aim of this study was to determine the chemical and botanical characterization of Chilean propolis samples and to evaluate their biological activity against the cariogenic bacteria Streptococcus mutans and Streptococcus sobrinus. Twenty propolis samples were obtained from beekeeping producers from the central and southern regions of Chile. The botanical profile was determined by palynological analysis. Total phenolic contents were determined using colorimetric assays. Reverse phase HPLC and HPLC-MS were used to determine the chemical composition. The minimum inhibitory concentration (MIC) was determined on S. mutans and S. sobrinus. All propolis samples were dominated by structures from native plant species. The characterization by HPLC/MS, evidenced the presence of quercetin, myricetin, kaempferol, rutine, pinocembrin, coumaric acid, caffeic acid and caffeic acid phenethyl ester, that have already been described in these propolis with conventional HPLC. Although all propolis samples inhibited the mutans streptococci growth, it was observed a wide spectrum of action (MIC 0.90 to 8.22 µg mL(-1)). Given that results it becomes increasingly evident the need of standardization procedures, where we combine both the determination of botanical and the chemical characterization of the extracts. Research conducted to date, describes a promising effectiveness of propolis in the prevention of caries and other diseases of the oral cavity, making it necessary to develop studies to identify and understand the therapeutic targets or mechanisms of molecular action of the various compounds present on them.

Chemical and botanical characterization of Chilean propolis and biological activity on cariogenic bacteria Streptococcus mutans and Streptococcus sobrinus

Propolis is a non-toxic natural substance with multiple pharmacological properties including anticancer, antioxidant, fungicidal, antibacterial, antiviral, and anti-inflammatory among others. The aim of this study was to determine the chemical and botanical characterization of Chilean propolis samples and to evaluate their biological activity against the cariogenic bacteria Streptococcus mutans and Streptococcus sobrinus. Twenty propolis samples were obtained from beekeeping producers from the central and southern regions of Chile. The botanical profile was determined by palynological analysis. Total phenolic contents were determined using colorimetric assays. Reverse phase HPLC and HPLC-MS were used to determine the chemical composition. The minimum inhibitory concentration (MIC) was determined on S. mutans and S. sobrinus. All propolis samples were dominated by structures from native plant species. The characterization by HPLC/MS, evidenced the presence of quercetin, myricetin, kaempferol, rutine, pinocembrin, coumaric acid, caffeic acid and caffeic acid phenethyl ester, that have already been described in these propolis with conventional HPLC. Although all propolis samples inhibited the mutans streptococci growth, it was observed a wide spectrum of action (MIC 0.90 to 8.22 µgmL-1). Given that results it becomes increasingly evident the need of standardization procedures, where we combine both the determination of botanical and the chemical characterization of the extracts. Research conducted to date, describes a promising effectiveness of propolis in the prevention of caries and other diseases of the oral cavity, making it necessary to develop studies to identify and understand the therapeutic targets or mechanisms of molecular action of the various compounds present on them.

Burkholderia cenocepacia O polysaccharide chain contributes to caspase-1-dependent IL-1beta production in macrophages.

Burkholderia cenocepacia infections in CF patients involve heightened inflammation, fatal sepsis, and high antibiotic resistance. Proinflammatory IL-1ß secretion is important in airway inflammation and tissue damage. However, little is known about this pathway in macrophages upon B. cenocepacia infection. We report here that murine macrophages infected with B. cenocepacia K56-2 produce proinflammatory cytokine IL-1ß in a TLR4 and caspase-1-mediated manner. We also determined that the OPS (O antigen) of B. cenocepacia LPS contributes to IL-1ß production and pyroptotic cell death. Furthermore, we showed that the malfunction of the CFTR channel augmented IL-1ß production upon B. cenocepacia infection of murine macrophages. Taken together, we identified eukaryotic and bacterial factors that contribute to inflammation during B. cenocepacia infection, which may aid in the design of novel approaches to control pulmonary inflammation.

Subdivision of the bacterioferritin comigratory protein family of bacterial peroxiredoxins based on catalytic activity.

Peroxiredoxins are ubiquitous proteins that catalyze the reduction of hydroperoxides, thus conferring resistance to oxidative stress. Using high-resolution mass spectrometry, we recently reclassified one such peroxiredoxin, bacterioferritin comigratory protein (BCP) of Escherichia coli, as an atypical 2-Cys peroxiredoxin that functions through the formation of an intramolecular disulfide bond between the active and resolving cysteine. An engineered E. coli BCP, which lacked the resolving cysteine, retained enzyme activity through a novel catalytic pathway. Unlike the active cysteine, the resolving cysteine of BCP peroxiredoxins is not conserved across all members of the family. To clarify the catalytic mechanism of native BCP enzymes that lack the resolving cysteine, we have investigated the BCP homologue of Burkholderia cenocepacia. We demonstrate that the B. cenocepacia BCP (BcBCP) homologue functions through a 1-Cys catalytic pathway. During catalysis, BcBCP can utilize thioredoxin as a reductant for the sulfenic acid intermediate. However, significantly higher peroxidase activity is observed utilizing glutathione as a resolving cysteine and glutaredoxin as a redox partner. Introduction of a resolving cysteine into BcBCP changes the activity from a 1-Cys pathway to an atypical 2-Cys pathway, analogous to the E. coli enzyme. In contrast to the native B. cenocepacia enzyme, thioredoxin is the preferred redox partner for this atypical 2-Cys variant. BCP-deficient B. cenocepacia exhibit a growth-phase-dependent hypersensitivity to oxidative killing. On the basis of sequence alignments, we believe that BcBCP described herein is representative of the major class of bacterial BCP peroxiredoxins. To our knowledge, this is the first detailed characterization of their catalytic activity. These studies support the subdivision of the BCP family of peroxiredoxins into two classes based on their catalytic activity.

Burkholderia cenocepacia O antigen lipopolysaccharide prevents phagocytosis by macrophages and adhesion to epithelial cells.

Chronic respiratory infections by the Burkholderia cepacia complex (Bcc) are of great concern to patients with cystic fibrosis. Bcc isolates may survive intracellularly within amoebae, respiratory epithelial cells and macrophages. The molecular mechanisms facilitating colonization and pathogenesis remain unclear. Given the importance of bacterial adhesion to host surfaces in microbial pathogenesis, we investigated the role of the O antigen LPS in the interaction of Burkholderia cenocepacia, a member of the Bcc, with macrophages and epithelial cells. Our results demonstrated that the O antigen modulates phagocytosis but does not affect intracellular survival of B. cenocepacia. Internalization of strains that lack O antigen was significantly increased compared to that of their isogenic smooth counterparts. However, no differences between rough and smooth strains were found in their ability to delay phagosomal maturation. We also found that the O antigen interfered with the ability of B. cenocepacia to adhere to bronchial epithelial cells, suggesting that this polysaccharide may mask one or more bacterial surface adhesins.

Biosynthesis and structure of the Burkholderia cenocepacia K56-2 lipopolysaccharide core oligosaccharide: truncation of the core oligosaccharide leads to increased binding and sensitivity to polymyxin B.

Burkholderia cenocepacia is an opportunistic pathogen that displays a remarkably high resistance to antimicrobial peptides. We hypothesize that high resistance to antimicrobial peptides in these bacteria is because of the barrier properties of the outer membrane. Here we report the identification of genes for the biosynthesis of the core oligosaccharide (OS) moiety of the B. cenocepacia lipopolysaccharide. We constructed a panel of isogenic mutants with truncated core OS that facilitated functional gene assignments and the elucidation of the core OS structure in the prototypic strain K56-2. The core OS structure consists of three heptoses in the inner core region, 3-deoxy-d-manno-octulosonic acid, d-glycero-d-talo-octulosonic acid, and 4-amino-4-deoxy-l-arabinose linked to d-glycero-d-talo-octulosonic acid. Also, glucose is linked to heptose I, whereas heptose II carries a second glucose and a terminal heptose, which is the site of attachment of the O antigen. We established that the level of core truncation in the mutants was proportional to their increased in vitro sensitivity to polymyxin B (PmB). Binding assays using fluorescent 5-dimethylaminonaphthalene-1-sulfonyl-labeled PmB demonstrated a correlation between sensitivity and increased binding of PmB to intact cells. Also, the mutant producing a heptoseless core OS did not survive in macrophages as compared with the parental K56-2 strain. Together, our results demonstrate that a complete core OS is required for full PmB resistance in B. cenocepacia and that resistance is due, at least in part, to the ability of B. cenocepacia to prevent binding of the peptide to the bacterial cell envelope.

A putative gene cluster for aminoarabinose biosynthesis is essential for Burkholderia cenocepacia viability.

Using a conditional mutagenesis strategy we demonstrate here that a gene cluster encoding putative aminoarabinose (Ara4N) biosynthesis enzymes is essential for the viability of Burkholderia cenocepacia. Loss of viability is associated with dramatic changes in bacterial cell morphology and ultrastructure, increased permeability to propidium iodide, and sensitivity to sodium dodecyl sulfate, suggesting a general cell envelope defect caused by the lack of Ara4N.