Expectation decreases brain susceptibility to fearful stimuli: ERP evidence from a modified emotion evaluation task

Expectation decreased the susceptibility to fearful stimuli in prior studies using distracting tasks. The present study tests whether expectation remains effective in decreasing this susceptibility, when subjects focus attention on emotional properties. Event-related potentials were recorded for fearful and neutral faces, while subjects performed a modified emotion evaluation task during unpredictable and predictable conditions. Behavioral data showed faster response latencies during predictable versus unpredictable conditions. ERP data showed prolonged peak latencies in N1 (80–130 ms) and larger amplitudes in P2 (130–180 ms) and N200-300 components, for unpredictable fearful versus neutral faces. Conversely, all these components showed similar responses to predictable fearful and neutral faces. Source analysis suggested that medial temporal lobe mediated ERPs elicited by unpredictable fearful faces, while ventromedial prefrontal cortex mediated those elicited by predictable fearful faces, in the 130–180 ms interval. Thus, we propose emotional expectation as a cognitive regulation strategy that reliably dampens human susceptibility to fearful stimuli.     

Highly purified lipoteichoic acid from gram-positive bacteria induces in vitro blood-brain barrier disruption through glia activation: role of pro-inflammatory cytokines and nitric oxide

The co-culture of bovine brain capillary endothelial cells and rat primary glial cells was established as an in vitro blood-brain barrier model to investigate the mechanisms by which the Gram-positive bacterial cell wall components lipoteichoic acid and muramyl dipeptide induced injury of blood-brain barrier structure and function. We found that highly purified lipoteichoic acid disrupted blood-brain barrier integrity in a concentration- and time-dependent manner indirectly, through glia activation. Low trans-endothelial electrical resistance and high permeability to fluorescein isothiocyanate-inulin observed in the presence of lipoteichoic acid-activated glial cells were potentiated by muramyl dipeptide and could be reversed only when glial cells were activated by lipoteichoic acid at 10 microg/ml but not with a higher lipoteichoic acid concentration (30 microg/ml). Immunocytochemistry analysis revealed no evident changes in the distribution of the cytoskeleton protein F-actin and tight junction proteins occludin and claudin after lipoteichoic acid treatment. However, the tight junction associated protein AHNAK clearly revealed the morphological alteration of the endothelial cells induced by lipoteichoic acid. Lipoteichoic acid-activated glial cells produced nitric oxide and pro-inflammatory cytokines (tumor necrosis factor-alpha and interleukin-1beta) that contributed to lipoteichoic acid-induced blood-brain barrier disruption, since the direct treatment of the endothelial monolayer with tumor necrosis factor-alpha or interleukin-1beta increased blood-brain barrier permeability, whereas the pre-treatment of lipoteichoic acid-activated glial cells with antibodies against these two cytokines blocked lipoteichoic acid effects. Additionally, nitric oxide was also involved in blood-brain barrier damage, since the nitric oxide donor itself (diethylenetriamine-nitric oxide adduct) increased blood-brain barrier permeability and inducible nitric oxide synthase inhibitor (1400W) partially reversed lipoteichoic acid-induced trans-endothelial electrical resistance decrease.     

A structural basis for Staphylococcal complement subversion: X-ray structure of the complement-binding domain of Staphylococcus aureus protein Sbi in complex with ligand C3d

The structure of the complement-binding domain of Staphylococcus aureus protein Sbi (Sbi-IV) in complex with ligand C3d is presented. The 1.7 Å resolution structure reveals the molecular details of the recognition of thioester-containing fragment C3d of the central complement component C3, involving interactions between residues of Sbi-IV helix α2 and the acidic concave surface of C3d. The complex provides a structural basis for the binding preference of Sbi for native C3 over C3b and explains how Sbi-IV inhibits the interaction between C3d and complement receptor 2. A second C3d binding site on Sbi-IV is identified in the crystal structure that is not observed in related S. aureus C3 inhibitors Efb-C and Ehp. This binding mode perhaps hints as to how Sbi-IV, as part of Sbi, forms a C3b-Sbi adduct and causes futile consumption of C3, an extraordinary aspect of Sbi function that is not shared by any other known Staphylococcal complement inhibitor.     

Immunotherapeutic strategies to combat staphylococcal infections

Antibiotic-resistant staphylococci are the leading cause of nosocomial infections in many hospitals around the world. Meanwhile, methicillin-resistant Staphylococcus aureus (MRSA) spread also in the community where highly virulent strains infect healthy adults that have no predisposing risk factors. Although a few novel antibiotics have been recently introduced into clinical practice, the search for alternative strategies to efficiently combat staphylococcal infections is urgently demanded to decrease the enormous burden caused by pathogenic staphylococci. In particular, immunological strategies based on vaccine development or therapeutic antibodies may significantly enhance the efficiency of anti-staphylococcal therapy. Most approaches are directed against surface components of staphylococci such as cell wall-linked adhesins, teichoic acids, capsule, the biofilm component PIA/PNAG, or soluble virulence determinants such as alpha-toxin, Panton-Valentine leukocidin, or superantigenic enterotoxins. Although 2 recent clinical trials have failed, several novel promising vaccines and therapeutic antibodies are currently in preclinical and clinical development.     

Resistance to linezolid in a methicillin-susceptible Staphylococcus aureus clinical isolate without previous exposure to oxazolidinones

A linezolid-resistant, methicillin-susceptible isolate of Staphylococcus aureus was obtained from an infected surgical wound in an ambulatory patient. The isolate belonged to ST125 and was susceptible to all the antibiotics tested except linezolid (MIC 8 μg/ml) and levofloxacin. Linezolid resistance could be ascribed to the presence of the mutation G2576T in 2 of the 23S rRNA alleles. The mutant alleles were stably maintained in the absence of antibiotic selection.     

Binding of the Staphylococcus aureus leucotoxin LukM to its leucocyte targets

The range of leucocytes susceptible to the leucotoxin LukM/F′, a two-component pore-forming toxin of Staphylococcus aureus causing mastitis in ruminants, had not been defined. We used fluorescent-labeled LukM to investigate the binding of this toxin to bovine cells and to identify its cellular targets among bovine, human and murine leucocytes. LukM bound to bovine blood neutrophils from all the individuals tested with similar affinity, with an apparent dissociation constant (Kd) of 1.81 ± 0.14 nM and 13?3100 ± 506 binding sites. The amount of LukM bound to bovine neutrophils did not depend on the presence of the complementary component LukF’, suggesting that the binding of LukM to its ligand does not depend on the formation of pore-forming oligomers, and that the number of bound LukM molecules corresponds to the number of available cell membrane ligands. Other staphylococcal class S components of bipartite leucotoxins (HlgA, HlgC, LukE, LukS-PV) were inefficient competitors of LukM for the binding to bovine neutrophils, indicating that LukM has a distinct ligand on target cells. Bovine blood neutrophils bound slightly more LukM than did milk neutrophils, and much more than did ovine and caprine blood neutrophils. Bovine monocytes and milk macrophages readily bound LukM, whereas blood lymphocytes did not. Human neutrophils bound little LukM and were resistant to LukM/F′ at the highest tested concentration (40 nM). Murine neutrophils bound LukM and were susceptible to the toxicity of LukM/F′, exhibiting flattening and nucleus alteration beginning at 0.3 nM concentration. Among murine peritoneal exudate cells, T lymphocytes (CD3+) and monocytes/macrophages (F4/80+) bound LukM, whereas binding to B lymphocytes (CD19+) was not detected. These results indicate that cells of the myeloid lineage are the main targets of LukM/F′ in dairy ruminants, and that resident or inflammatory migrated phagocytes are susceptible to this toxin.     

Responses of Staphylococcus aureus bacterial cells to nanocrystalline nickel nanostructures

A broad range of human diseases are associated with bacterial infections, often initiated by specific adhesion of a bacterium to the target environment. Despite the significant role of bacterial adhesion in human infectious diseases, details and mechanisms of bacterial adhesion have remained elusive. Herein, we study the physical interactions between Staphylococcus aureus, a type of micro-organism relevant to infections associated with medical implants, and nanocrystalline (nc) nickel nanostructures with various columnar features, including solid core, hollow, x-shaped and c-shaped pillars. Scanning electron microscopy results show the tendency of these bacterial cells to attach to the nickel nanostructures. Moreover, unique single bacterium attachment characteristics were observed on nickel nanostructures with dimensions comparable to the size of a single bacterium.     

A CD40 and an NCOA5 gene polymorphism confer susceptibility to psoriasis in a Southern European population: a case-control study

Recent genome-wide association studies of many complex diseases have successfully identified novel susceptibility loci, with many of them shared by multiple disease-associated pathways. The genes CD40 and nuclear receptor coactivator 5 (NCOA5), located in a 400-kb region surrounding CD40, have been reported to be associated with increased risk for rheumatoid arthritis and other autoimmune diseases. We hypothesized that those genes may also have a role in psoriasis (PS), an autoimmune, chronic inflammatory skin disease. In a case-control study, 198 patients with PS and 400 controls were genotyped for 2 single nucleotide polymorphisms (SNPs) of the CD40 and NCOA5 genes located on chromosome 20q.12-q13.12. Here, we demonstrate for the first time the association of both SNPs with susceptibility to PS, thus suggesting a putative key role of both genes in multiple autoimmune diseases. Alleles G and C of the CD40 rs4810485 and NCOA5 rs2903908 SNPs, respectively, were more common in individuals with PS than in controls (p = 0.03, odds ratio [OR] = 1.42, 95% confidence interval [95% CI] 1.05-1.95 and p = 0.000 003, OR = 1.93, 95% CI 1.47-2.55, respectively). The identification of shared genetic susceptibility loci may provide insight into our understanding of the pathophysiology of autoimmune diseases.     

Methicillin resistance in Staphylococcus isolates: The “mec alphabet” with specific consideration of mecC, a mec homolog associated with zoonotic S. aureus lineages

Livestock-associated (LA) methicillin-resistant Staphylococcus aureus (MRSA) have globally emerged during the past decade. In Europe, this was particularly due to the occurrence of LA-MRSA strains associated with the clonal complex (CC) 398 as defined by multilocus sequence typing. However, more recently animal-adapted clonal lineages of S. aureus showing phenotypic methicillin resistance have been identified such as CC130, CC599, CC59, CC1943 and CC425. These newly emerging LA-MRSA CCs/STs caused infections in animals and zoonoses in humans. In contrast to other S. aureus clonal lineages, the methicillin resistance of the latter CCs/STs is based on a mecA gene homolog, designated mecC, which is part of a distinct SCCmec type (SCCmec XI). Including mecB found in Macrococcus caseolyticus, henceforth, the “mec alphabet” comprises three major gene types with several allotypes. As known for mecA, the gene homolog mecC is also not restricted to S. aureus, but found in several staphylococcal species including S. sciuri, S. stepanovicii and S. xylosus (mecC1 allotype). First investigations showed a wide geographical distribution of mecC-MRSA in Europe and a broad diversity of host species including livestock, companion and wildlife animals. In particular, wild rodents and insectivores might serve as reservoir for staphylococci harboring mecC. Economic burden may be caused by mastitis of dairy cattle. Livestock animals may likely serve as source for human infections with mecC-MRSA; reported cases comprise skin and soft tissue infections, osteomyelitis and bacteremia. Due to the divergent molecular nature of mecC-MRSA, its diagnostics is hampered by difficulties to verify the methicillin resistance using phenotypic as well as DNA-based procedures, which could have negative consequences for therapy of mecC-MRSA-caused infections.     

Identification of a novel psoriasis susceptibility locus at 1p and evidence of epistasis between PSORS1 and candidate loci

The pathogenesis of all forms of psoriasis remains obscure. Segregation analysis and twin studies together with ethnic differences in disease frequency all point to an underlying genetic susceptibility to psoriasis, which is both complex and likely to reflect the action of a number of genes. We performed a genome wide analysis using a total of 271 polymorphic autosomal markers on 284 sib relative pairs identified within 158 independent families. We detected evidence for linkage at 6p21 (PSORS1) with a non-parametric linkage score (NPL)=4.7, p=2 × 10^-6 and at chromosome 1p (NPL=3.6, p=1.9 × 10^-4) in all families studied. Significant excess (p=0.004) paternal allele sharing was detected for markers spanning the PSORS1 locus. A further three regions reached NPL scores of 2 or greater, including a region at chromosome 7 (NPL 2.1), for which linkage for a number of autoimmune disorders has been reported. Partitioning of the data set according to allele sharing at 6p21 (PSORS1) favoured linkage to chromosomes 2p (NPL 2.09) and 14q (NPL 2.0), both regions implicated in previous independent genome scans, and suggests evidence for epistasis between PSORS1 and genes at other genomic locations. This study has provided linkage evidence in favour of a novel susceptibility locus for psoriasis and provides evidence of the complex mechanisms underlying the genetic predisposition to this common skin disease.


Keywords: psoriasis; PSORS1; epistasis     

Comparison of Genotypes and Enterotoxin Genes Between Staphylococcus aureus Isolates from Blood and Nasal Colonizers in a Korean Hospital

In this study, we investigated the genetic background of 70 Staphylococcus aureus isolates (36 methicillin-resistant S. aureus [MRSA] and 34 methicillin-susceptible S. aureus [MSSA]) obtained from blood at a Korean tertiary-care hospital, using spa typing, multilocus sequence typing, and SCCmec typing. In addition, the prevalence of enterotoxin (sea, seb, sec, sed, see, seg, seh, sei, and sek), tst, and pvl genes among the samples was assessed via polymerase chain reaction, and the results were compared with those of 95 isolates of S. aureus obtained from nasal swabs. All MRSA isolates from blood, except one, belonged to three major clones: sequence type (ST)5-MRSA-II, ST72-MRSA-II (or IVA), and ST239-MRSA-III, among which ST5-MRSA-II was the predominant clone. The prevalence of enterotoxin genes in the S. aureus isolates obtained from blood differed significantly from those from the nasal swabs for the sea, seb, sec, and seh gene. In particular, the seb and sec genes were detected exclusively in the MRSA isolates of ST5 or spa-CC002, thereby suggesting the co-adaptation of virulence genes with the genetic background and their contribution to biological fitness.     

Role of insertion elements and yycFG in the development of decreased susceptibility to vancomycin in Staphylococcus aureus

The glycopeptide antibiotic vancomycin acts by binding to the D-alanyl-D-alanine terminus of the cell wall precursor lipid II in the cytoplasmic membrane. The purpose of this study was the identification of genes that might be involved in the vancomycin resistance mechanism. To this end, the expression profiles of two vancomycin intermediately resistant Staphylococcus aureus (VISA) strains, the clinical isolate S. aureus SA137/93A (Etest: 8 microg/ml) and its laboratory mutant S. aureus SA137/93G (Etest: 12 microg/ml) were analyzed using an S. aureus full-genome chip. The results indicated that an essential two-component regulatory system, yycF (vicR) and yycG (vicK) was drastically up-regulated in strain SA137/93A. Sequencing of the yycFG promoter region of strain SA137/93A revealed an insertion of IS256 in the predicted promoter region creating a potentially stronger hybrid promoter. In strain SA137/93G, IS256 was not integrated in the yycFG promoter region but, in previous studies, a copy of IS256 had been found to inactivate the tcaA gene (Maki et al. Antimicrob. Agents and Chemother. 48, 1953-1959 (2004)). Detailed population analyses showed that, in addition to the loss of SCCmec, the inactivation of tcaA seems to cause at least part of the increase in teicoplanin and vancomycin resistance in strain SA137/93G.     

Systemic dissemination and cutaneous damage in a mouse model of staphylococcal skin infections

Serious staphylococcal infections frequently begin in the skin. The present study used a mouse model of such infections to evaluate the ability of Staphylococcus aureus to disseminate from the skin and to determine if cutaneous damage from the infections was required for dissemination. The mice were inoculated with S. aureus onto flank skin prepared by a tape-stripping method that caused minimal disruption of the epidermal keratinocyte layers. After these inoculations the staphylococci were found to disseminate to the spleen and kidneys of almost all animals within 6 h. Induction of leucopenia did not affect this process. Cutaneous damage was prominent in these experimental infections and included loss of the epidermis, neutrophil infiltration into the epidermis, and complete necrosis of the dermis. The latter also occurred in cyclophosphamide-treated animals, indicating that the organisms themselves and not the host inflammatory responses were responsible. Dermal necrosis did not develop until 48 h after inoculation, a time by which dissemination had already occurred. Therefore, in this mouse model system S. aureus is capable of penetrating the epidermal keratinocyte layers and disseminating rapidly after inoculation; the experimental infections do produce significant dermal damage, but the latter develops after dissemination has already taken place.     

PHACOS,a functionalized bacterial polyester with bactericidal activity against methicillin-resistant Staphylococcus aureus

Biomaterial-associated infections represent a significant clinical problem, and treatment of these microbial infections is becoming troublesome due to the increasing number of antibiotic-resistant strains. Here, we report a naturally functionalized bacterial polyhydroxyalkanoate (PHACOS) with antibacterial properties. We demonstrate that PHACOS selectively and efficiently inhibits the growth of methicillin-resistant Staphylococcus aureus (MRSA) both in vitro and in vivo. This ability has been ascribed to the functionalized side chains containing thioester groups. Significantly less (3.2-fold) biofilm formation of S. aureus was detected on PHACOS compared to biofilms formed on control poly(3-hydroxyoctanoate-co-hydroxyhexanoate) and poly(ethylene terephthalate), but no differences were observed in bacterial adhesion among these polymers. PHACOS elicited minimal cytotoxic and inflammatory effects on murine macrophages and supported normal fibroblast adhesion. In vivo fluorescence imaging demonstrated minimal inflammation and excellent antibacterial activity for PHACOS compared to controls in an in vivo model of implant-associated infection. Additionally, reductions in neutrophils and macrophages in the vicinity of sterile PHACOS compared to sterile PHO implant were observed by immunohistochemistry. Moreover, a similar percentage of inflammatory cells was found in the tissue surrounding sterile PHACOS and S. aureus pre-colonized PHACOS implants, and these levels were significantly lower than S. aureus pre-colonized control polymers. These findings support a contact active surface mode of antibacterial action for PHACOS and establish this functionalized polyhydroxyalkanoate as an infection-resistant biomaterial.     

Binding of a Staphylococcus aureus bone pathogen to type I collagen

We contrasted the collagen-binding potential of the experimental osteomyelitis pathogen, Staphylococcus aureus strain SMH, to several other strains. These included Cowan 1 (binder), Wood 46 (non-binder) and six capsular variants. These measurements were made using an ¹²⁵I-collagen binding assay. Formalin-killed S. aureus SMH strongly bound commercial type I iodinated collagen (dissociation contant, K_d = 2 × 10⁻⁹ m). The extent of binding was similar to Cowan 1. Binding was saturable and not inhibited by 100 m solutions of -glucose, -galactose, -mannose, methyl-α- -fucopyranoside, -hydroxyproline or -glycine. -lactose gave moderate inhibition of binding to collagen, and -fucose was strongly inhibitory. Trypsinized SMH did not bind collagen. None of four Ruthenium-red-staining staphylococci (encapsulated) avidly bound type I collagen. The encapsulated Smith strain, for example, did not bind to collagen but its capsule-negative variant, Smith compact, showed extensive binding. Three of five non-encapsulated S. aureus were strong collagen binders. These data suggest that the prototype bone pathogen binds to the major protein component of bone's extracellular matrix. Collagen-binding is promoted by protein adhesin(s), not capsule. The latter, in fact, appeared to interfere with this interaction. Binding was inhibited by solutions containing the simple monosaccharide, -fucose.     

Pathogenesis of chronic rhinosinusitis: inflammation

Chronic rhinosinusitis (CRS) is a heterogeneous group of inflammatory diseases of the nasal and paranasal cavities either accompanied by polyp formation (CRSwNP) or without polyps (CRSsNP). CRSsNP and CRSwNP are prevalent medical conditions associated with substantial impaired quality of life, reduced workplace productivity, and serious medical treatment costs. Despite recent research evidence that contributes to further unveiling the pathophysiology of these chronic airway conditions, the cause remains poorly understood and appears to be multifactorial. A?diverse spectrum of alterations involving histopathology, inflammatory cell and T-cell patterns, remodeling parameters (eg, TGF-β), eicosanoid and IgE production, microorganisms, and epithelial barrier malfunctions is reported in the search to describe the pathogenesis of this heterogeneous group of upper airway diseases. Furthermore, novel evidence indicates considerable heterogeneity within the CRSwNP subgroup determining the risk of comorbid asthma. The characterization of specific disease subgroups is a challenging scientific and clinical task of utmost importance in the development of diagnostic tools and application of individualized treatments. This review focuses on recent evidence that sheds new light on our current knowledge regarding the inflammatory process of CRS to further unravel its pathogenesis.     

Intragenomic and intraspecific heterogeneity of the 16S rRNA gene in seven bacterial species from the respiratory tract of cystic fibrosis patients assessed by PCR-Temporal Temperature Gel Electrophoresis

16S rRNA gene-based cultivation-independent methods are increasingly used to study the diversity of microbiota during health and disease. One bias of these methods is the variability of 16S rRNA gene that may exist among strains of a same species (intraspecific heterogeneity) or between rrs copies in a genome (intragenomic heterogeneity). We evaluated the level of intraspecific and intragenomic 16S rDNA variability in seven species frequently encountered in respiratory tract samples in cystic fibrosis (CF). A total of 179 strains were subjected to V3 region 16S rDNA PCR-TTGE. Using this easy-to-perform and rapid method, different levels of V3 region rrs heterogeneity were demonstrated. No intraspecific and intragenomic rrs heterogeneity was demonstrated for Moraxella catarrhalis (n=16), Pseudomonas aeruginosa (n=31) and Streptococcus pneumoniae (n=14) showing a single PCR-TTGE band characteristic of the species. Low level of intraspecific heterogeneity was observed for Staphylococcus aureus (n=30), Stenotrophomonas maltophilia (n=29) and Achromobacter xylosoxidans (n=28), and 17%, 38% and 96% of these strains showed intragenomic heterogeneity (two to four different rrs copies), respectively. Haemophilus influenzae (n=31) displayed the higher level of intraspecific variability with 23 different PCR-TTGE patterns and 61% of the strains showed intragenomic rrs heterogeneity (two to four different rrs copies). Although only one hypervariable region of the 16S rRNA gene was explored, intraspecific and intragenomic rrs heterogeneity was frequently observed in this study and should be taken into consideration for a better interpretation of 16S rRNA gene-based diversity profiles in denaturing gels and to avoid any overestimation of the respiratory microbiota diversity in CF.     

Characterization of 1706, a virulent phage from Lactococcus lactis with similarities to prophages from other Firmicutes

The virulent lactococcal phage 1706, isolated in 1995 from a failed cheese production in France, represents a new lactococcal phage species of the Siphoviridae family. This phage has a burst size of 160 and a latent period of 85 min. Its linear double-stranded DNA genome was composed of 55,597 bp with a 33.7% G+C content. Its deduced proteome (76 ORFs) shared limited similarities to other known phage proteins. SDS-PAGE coupled with LC-MS/MS analyses led to the identification of 15 structural proteins. The most striking feature of the 1706 proteome was that 22 ORFs shared similarities with proteins deduced from the genome of either Ruminococcus torques and/or Clostridium leptum. Both are Firmicutes bacteria found in the gut flora of humans. We also identified a four-gene module in phage 1706, most likely involved in host recognition that shared similarities with lactococcal prophages. We propose that the virulent phage 1706 infected another bacterial genus before picking up a lactococcal host recognition module.