Molecular Basis of Virulence in Staphylococcus aureus Mastitis

S. aureus is one of the main pathogens involved in ruminant mastitis worldwide. The severity of staphylococcal infection is highly variable, ranging from subclinical to gangrenous mastitis. This work represents an in-depth characterization of S. aureus mastitis isolates to identify bacterial factors involved in severity of mastitis infection

Evidence for Reductive Genome Evolution and Lateral Acquisition of Virulence Functions in Two Corynebacterium pseudotuberculosis Strains

Ruiz JC, D'Afonseca V, Silva A, et al. Evidence for Reductive Genome Evolution and Lateral Acquisition of Virulence Functions in Two Corynebacterium pseudotuberculosis Strains. PLoS ONE. 2011;6(4): e18551.Background: Corynebacterium pseudotuberculosis, a Gram-positive, facultative intracellular pathogen, is the etiologic agent of the disease known as caseous lymphadenitis (CL). CL mainly affects small ruminants, such as goats and sheep; it also causes infections in humans, though rarely. This species is distributed worldwide, but it has the most serious economic impact in Oceania, Africa and South America. Although C. pseudotuberculosis causes major health and productivity problems for livestock, little is known about the molecular basis of its pathogenicity. Methodology and Findings: We characterized two C. pseudotuberculosis genomes (Cp1002, isolated from goats; and CpC231, isolated from sheep). Analysis of the predicted genomes showed high similarity in genomic architecture, gene content and genetic order. When C. pseudotuberculosis was compared with other Corynebacterium species, it became evident that this pathogenic species has lost numerous genes, resulting in one of the smallest genomes in the genus. Other differences that could be part of the adaptation to pathogenicity include a lower GC content, of about 52%, and a reduced gene repertoire. The C. pseudotuberculosis genome also includes seven putative pathogenicity islands, which contain several classical virulence factors, including genes for fimbrial subunits, adhesion factors, iron uptake and secreted toxins. Additionally, all of the virulence factors in the islands have characteristics that indicate horizontal transfer. Conclusions: These particular genome characteristics of C. pseudotuberculosis, as well as its acquired virulence factors in pathogenicity islands, provide evidence of its lifestyle and of the pathogenicity pathways used by this pathogen in the infection process. All genomes cited in this study are available in the NCBI Genbank database (http://www.ncbi.nlm.nih.gov/genbank/) under accession numbers CP001809 and CP001829

Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign

Abstract: In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass ∼6.5 × 109 M ⊙. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87’s spectrum. We can exclude that the simultaneous γ-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the γ-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded

Distinct alterations in sublingual microcirculatory blood flow and hemoglobin oxygenation in on-pump and off-pump coronary artery bypass graft surgery

The authors hypothesized that cardiopulmonary bypass (CPB) (on-pump) is associated with more severe changes in the microcirculatory blood flow and tissue oxygenation as compared with off-pump coronary artery bypass surgery. An observational study. A university hospital and teaching hospital. Patients undergoing on-pump (n = 24) or off-pump (n = 24) cardiac surgery. Microcirculatory measurements were performed before CPB and 10 minutes after the switch to CPB or before and during cardiac luxation in off-pump patients. Sublingual microcirculatory perfusion was investigated using side-stream dark field imaging, and sublingual microcirculatory oxygenation was measured using reflectance spectrophotometry. Conversion to CPB resulted in an increase in cardiac output from 4.0 ± 0.2 to 4.8 ± 0.3 L/min (p < 0.01) and a 40% reduction in arterial hemoglobin concentration. Cardiopulmonary bypass was associated with an increase in venular blood velocity from 349 ± 201 μm/s to 563 ± 227 μm/s (p < 0.05), a reduction in functional capillary density of 43%, and an increase in hemoglobin oxygenation of the red blood cells in the remaining filled capillaries from 47.2% ± 6.1% to 59.7% ± 5.2% (p < 0.001). The decrease in cardiac output during cardiac luxation from 4.5 ± 1.7 to 1.8 ± 0.8 L/min (p < 0.01) without hemoglobin changes was associated with a complete halt of capillary blood flow and a reduction in maximum capillary blood velocity from 895 ± 209 to 396 ± 178 μm/s (p < 0.01). The functional capillary density remained unchanged, whereas the hemoglobin oxygenation declined from 64.2% ± 9.1% to 48.6% ± 8.7% (p < 0.01). On-pump and off-pump cardiac surgery are associated with distinct alterations in sublingual microcirculatory perfusion and hemoglobin oxygenation. Although on-pump surgery results in a fall out of capillaries resulting in decreased oxygen extraction, off-pump surgery results in a cessation of flow during luxation resulting in decreased convection of oxygen transpor

[i]Staphylococcus aureus[/i] proteins differentially recognized by the ovine immune response in mastitis or nasal carriage

Staphylococcus aureus is an opportunistic pathogen in dairy ruminants where it is a major cause of mastitis and can be also found in healthy carriage. A better knowledge of the host-pathogen interactions is needed to tackle this serious animal health problem. This study aimed at identifying S. aureus proteins differentially expressed during nasal colonization versus mastitis. Serological proteome analysis (SERPA) was used to examine protein samples prepared from culture supernatants of S. aureus strains originally isolated from gangrenous mastitis and nasal carriage (O11) or subclinical mastitis (O46) and to compare patterns of immune-reactive proteins. These staphylococcal proteins were revealed by sera obtained from ewes suffering from S. aureus mastitis and by sera obtained from healthy nulliparous ewes (i.e. no lactation and no mastitis or other symptoms) that were nasally colonized by S. aureus. Altogether 49 staphylococcal immune-reactive proteins were identified in this study. Patterns of proteins revealed by sera from infected- or healthy carrier- animals were comparable and analysis singled out one immune-reactive protein, an N-acetylmuramyl-L-alanine amidase, which was recognized by each of the 6 sera from infected animals, when tested individually, and not by the sera of healthy carriers. This is the first study that compares the S. aureus seroproteome in colonization versus mastitis context in ruminants. These results open avenues for studies aiming at a better understanding of the balance between infection and commensal lifestyle in this opportunistic pathogen and at new prevention strategies

Molecular basis of virulence in Staphylococcus aureus ovine mastitis

Egalement paru dans la revue "Journal of Animal Science", Vol.89, E-Suppl.1S. aureus is one of the main pathogens involved in ruminant mastitis worldwide. The severity of staphylococcal infection is highly variable, ranging from subclinical to gangrenous mastitis and is dependent on host as well as bacterial factors. This work represents an in-depth characterization of S. aureus mastitis isolates to identify bacterial factors involved in severity of mastitis infection. We employed genomic, transcriptomic and proteomic approaches to comprehensively compare two clonally related S. aureus strains that were responsible for severe (strain O11) and milder (strain O46) mastitis in ewes, respectively. Variation in the content of mobile genetic elements, iron acquisition and metabolism, transcriptional regulation and exoprotein production was observed. In particular, O11 produced relatively high levels of exoproteins, including toxins and proteases known to be important in virulence. a characteristic we observed in other S. aureus strains isolated from clinical mastitis cases. Our data are consistent with a dose-dependant role of some staphylococcal factors in the hypervirulence of strains isolated from severe mastitis. Mobile genetic elements, transcriptional regulators, exoproteins and iron acquisition pathways constitute good targets for further research to define the underlying mechanisms of mastitis severity

[i]Staphylococcus aureus[/i] proteins differentially recognized by the ovine immune response in mastitis or nasal carriage

Staphylococcus aureus is an opportunistic pathogen in dairy ruminants where it is found in healthy carriage and can be a major cause of mastitis. A better knowledge of the host– pathogen interactions is needed to tackle this serious animal health problem. This study aimed at identifying S. aureus proteins differentially expressed by S. aureus in nasal colonization versus mastitis. Serological proteome analysis (SERPA) was used to examine protein samples prepared from culture supernatants of S. aureus strains originally isolated from gangrenous mastitis and nasal carriage (O11) or subclinical mastitis (O46) and tocompare patterns of immune-reactive proteins. These staphylococcal proteins were revealed by sera obtained from ewes suffering from S. aureus mastitis and by sera obtained from healthy nulliparous ewes (i.e. no lactation and no mastitis or other symptoms) that were nasally colonized by S. aureus. Altogether 49 staphylococcal immune-reactive proteins were identified in this study. Patterns of proteins revealed by sera from infectedorhealthy carrier- animals were comparable and analysis singled out one immunereactiveprotein, N-acetylmuramyl-L-alanine amidase, which was recognized by each of the 6 sera from infected animals, when tested individually, and not by the sera of healthy carriers. This is the first study that compares the S. aureus seroproteome in colonization versus mastitis context in ruminants. These results open avenues for studies aiming at a better understanding of the balance between infection and commensal lifestyle in this opportunistic pathogen and at new prevention strategies

La caractérisation omique de souches de Staphylococcus aureus isolées de mammites ovines révèle une forte proximité génétique mais des transcriptomes et protéomes associés à des tableaux cliniques radicalement différents

Staphylococcus aureus est un des pathogènes majeurs impliqués dans les mammites chez les ruminants. Les symptômes associés varient selon la sévérité des mammites (de la mammite subclinique à la mammite gangréneuse). L’origine de cette variabilité (virulence du pathogène/susceptibilité de l’hôte) n’est pas clairement établie à ce jour. Afin d’identifier les différences entre des souches de S. aureus impliquées dans des mammites de degrés de sévérité différents, nous avons comparé deux souches de S. aureus isolées de mammites gangréneuse (O11) et subclinique (O46) et reproduisant des tableaux cliniques distincts lors d’infections expérimentales en modèle brebis. Les deux souches ont été séquencées (Illumina) et leur transcriptome (puce pangénomique) et protéome (électrophorèse 2D) ont été analysés et comparés dans des conditions mimant le contexte mammite. O11 et O46 sont génotypiquement et génétiquement proches à un prophage (présent dans la souche O46) et quelques gènes présentant des insertions/délétions près. A l’inverse, les analyses protéomiques et transcriptomiques ont montré des différences majeures entre les deux souches. O11 produit plus de toxines et de protéases que la souche O46 mais moins de composés de surface (adhésines, capsule), quelle que soit la phase de croissance. Il est à noter que le système agr est fonctionnel et que son expression est identique dans les deux souches. Ces résultats ont été confirmés sur d’autres souches de S. aureus isolées de mammites ovines présentant des degrés de sévérité différents. De façon remarquable, nous avons observé plusieurs différences inter-souches dans des gènes impliqués dans le métabolisme du fer. Ainsi, O11 surexprime des gènes impliqués dans l’acquisition du fer (isdH, sbnC, opéron sir) alors que O46 présente en plus d’une sous expression de ces gènes, des délétions sur les gènes isdH et hrtB. L’expression de ces gènes chez les souches de S. aureus isolées de mammites pourrait être un élément clé dans le pouvoir infectieux au sein de la glande mammaire. Ces résultats montrent que, même si O11 et O46 ont en théorie un potentiel de virulence équivalent (comparaison génomique / contenu en gènes similaire), la capacité d’expression des facteurs de virulence ainsi que la capacité d’adaptation au contexte infectieux, (comparaison transcriptomique et protéomique) varient entre les deux souches et pourraient être à l’origine des degrés de sévérités distincts observés en contexte mammit

Molecular basis of virulence in staphylococcus aureus mastitis

Staphylococcus aureus is a major pathogen in ruminant mastitis. Staphylococcal mastitis in ovine hosts is remarkably variable in terms of acuteness and ranges from subclinical to gangrenous mastitis. S. aureus factors involved in such variations are still poorly documented. This study aimed at identifying the staphylococcal factors responsible for the acuteness of the infection. Two S. aureus strains, isolated from gangrenous (O11) or subclinical (O46) ewe mastitis, were selected for this work. Despite a close phylogenetic relationship, these strains were shown to reproducibly induce severe (O11) or mild (O46) symptoms in experimental ewe mastitis. Several omic approaches were combined to compare these two strains. Both strains were fully sequenced and their transcriptome and proteome were analyzed in culture conditions mimicking mastitis context. Results showed that dramatic differences between O11 and O46 rely on their ability to adapt to and to express their virulence in a mammary context rather than in their gene content. This study highlights differences in the expression of genes related to mobile genetic elements (especially prophages), the expression of genes involved in iron acquisition and metabolism, of transcriptional factors (SigmaB and SigmaS) and in exoprotein production. Serological Proteome Analysis (SERPA) showed that most of these exoproteins are indeed produced during mastitis. Analysis of 10 other S. aureus strains, focused on two of these exoproteins –SspB and a protein of unknown function- showed SspB is produced only in strains isolated from severe mastitis and the protein of unknown function in strains isolated from subclinical mastitis. The exact role of the genes identified here (exoproteins, mobile genetic elements, iron metabolism and acquisition) in the infection and in mastitis acuteness remains to be determined. Finally, we showed that O11 is transformable and can thus be subjected to mutagenesis. The genes identified here represent excellent candidates for targeted studies of the molecular basis of S. aureus pathogenesis in ruminant mastitis

Molecular basis of virulence in staphylococcus aureus mastitis

Staphylococcus aureus is a major pathogen in ruminant mastitis. Staphylococcal mastitis in ovine hosts is remarkably variable in terms of acuteness and ranges from subclinical to gangrenous mastitis. S. aureus factors involved in such variations are still poorly documented. This study aimed at identifying the staphylococcal factors responsible for the acuteness of the infection. Two S. aureus strains, isolated from gangrenous (O11) or subclinical (O46) ewe mastitis, were selected for this work. Despite a close phylogenetic relationship, these strains were shown to reproducibly induce severe (O11) or mild (O46) symptoms in experimental ewe mastitis. Several omic approaches were combined to compare these two strains. Both strains were fully sequenced and their transcriptome and proteome were analyzed in culture conditions mimicking mastitis context. Results showed that dramatic differences between O11 and O46 rely on their ability to adapt to and to express their virulence in a mammary context rather than in their gene content. This study highlights differences in the expression of genes related to mobile genetic elements (especially prophages), the expression of genes involved in iron acquisition and metabolism, of transcriptional factors (SigmaB and SigmaS) and in exoprotein production. Serological Proteome Analysis (SERPA) showed that most of these exoproteins are indeed produced during mastitis. Analysis of 10 other S. aureus strains, focused on two of these exoproteins –SspB and a protein of unknown function- showed SspB is produced only in strains isolated from severe mastitis and the protein of unknown function in strains isolated from subclinical mastitis. The exact role of the genes identified here (exoproteins, mobile genetic elements, iron metabolism and acquisition) in the infection and in mastitis acuteness remains to be determined. Finally, we showed that O11 is transformable and can thus be subjected to mutagenesis. The genes identified here represent excellent candidates for targeted studies of the molecular basis of S. aureus pathogenesis in ruminant mastitis