Emergence of Amoxicillin-Resistant Variants of Spain9V-ST156 Pneumococci Expressing Serotype 11A Correlates with Their Ability to Evade the Host Immune Response

Capsular switching allows pre-existing clones of Streptococcus pneumoniae expressing vaccine serotypes to escape the vaccine-induced immunity by acquisition of capsular genes from pneumococci of a non-vaccine serotype. Here, we have analysed the clonal composition of 492 clinical isolates of serotype 11A causing invasive disease in Spain (2000–2012), and their ability to evade the host immune response. Antibiograms, serotyping and molecular typing were performed. The restriction profiles of pbp2x, pbp1a and pbp2b genes were also analysed. Interaction with the complement components C1q, C3b, C4BP, and factor H was explored whereas opsonophagocytosis assays were performed using a human cell line differentiated to neutrophils. Biofilm formation and the polymorphisms of the major autolysin LytA were evaluated. The main genotypes of the 11A pneumococci were: ST62 (447 isolates, 90.6%), followed by ST6521 (35 isolates, 7.3%) and ST838 (10 isolates, 2.1%). Beta lactam resistant serotype 11A variants of genotypes ST838 and ST6521 closely related to the Spain^9V-ST156 clone were first detected in 2005. A different pattern of evasion of complement immunity and phagocytosis was observed between genotypes. The emergence of one vaccine escape variant of Spain^9V-ST156 (ST6521^11A), showing a high potential to avoid the host immune response, was observed. In addition, isolates of ST6521^11A showed higher ability to produce biofilms than ST838^11A or ST62^11A, which may have contributed to the emergence of this PEN-resistant ST6521^11A genotype in the last few years. The emergence of penicillin-resistant 11A invasive variants of the highly successful ST156 clonal complex merits close monitoring.     

Infectivity,viability and effects of Paranosema locustae (Microsporidia) on juveniles of Dichroplus maculipennis (Orthoptera: Acrididae: Melanoplinae) under laboratory conditions

Infectivity and effects on host of a long-term stored aqueous suspension of Paranosema locustae on juveniles of Dichroplus maculipennis, a pest grasshopper in parts of the Pampas and Patagonia, were evaluated. Infections developed in 90–97.8% of treated individuals. Mortality increased with time, reaching highest values at 30–40 days post-inoculation (79.5–100%). Infected nymphs showed significantly slower development.     

Characterization of Salmonella enterica Serovar Typhimurium from Marine Environments in Coastal Waters of Galicia (Spain)

Twenty-three Salmonella enterica serovar Typhimurium isolates from marine environments were characterized by phage typing, pulsed-field gel electrophoresis (PFGE) analysis, plasmid analysis, and antibiotic resistance, and the distribution of the different types in the coastal waters were subsequently analyzed. Five phage types were identified among the isolates (PT41, PT135, PT99, DT104, and DT193). PT135 isolates were exclusively detected during the winter months from 1998 to 2000, whereas DT104 and PT41 isolates were detected exclusively in the summer months from 2000 to 2002. XbaI PFGE analysis revealed 9 PFGE types, and plasmid profiling identified 8 plasmid types (with 1 to 6 plasmids) among the isolates. Only three isolates presented multidrug resistance to antibiotics. Two DT104 isolates were resistant to 8 and 7 antibiotics (profiles ACCeFNaSSuT and ACeFNeSSuT), whereas a PT193 isolate presented resistance to 6 antibiotics (profile ACFSSu). In addition, four PT41 isolates were resistant to a single antibiotic. The detection of multidrug-resistant phage types DT104 and DT193 in shellfish emphasizes the importance of monitoring the presence of Salmonella in routine surveillance of live bivalve molluscs.     

Polymorphism in a common Atlantic reef coral (Montastraea cavernosa) and its long-term evolutionary implications

Recent advances in morphometrics and genetics have led to the discovery of numerous cryptic species in coral reef ecosystems. A prime example is the Montastraea annularis scleractinian coral species complex, in which morphological, genetic, and reproductive data concur on species boundaries, allowing evaluation of long-term patterns of speciation and evolutionary innovation. Here we test for cryptic species in the Atlantic species, Montastraea cavernosa, long recognized as polymorphic. Our modern samples consist of 94 colonies collected at four locations (Belize, Panamá, Puerto Rico in the Caribbean; S?o Tomé in the Eastern Atlantic). Our fossil samples consist of 78 colonies from the Plio-Pleistocene of Costa Rica and Panamá. Landmark morphometric data were collected on thin sections of 46 modern and 78 fossil colonies. Mahalanobis distances between colonies were calculated using Bookstein coordinates, revealing two modern and four fossil morphotypes. The remaining 48 of the 94 modern colonies were assigned to morphotype using discriminant analysis of calical measurements. Cross-tabulation and multiple comparisons tests show no significant morphological differences among geographic locations or water depths. Patterns of variation within and among fossil morphotypes are similar to modern morphotypes. DNA sequence data were collected for two polymorphic nuclear loci (β-tub1 and β-tub2) on all 94 modern colonies. Haplotype networks show that both genes consist of two clades, but morphotypes are not associated with genetic clades. Genotype frequencies and two-locus genotype assignments indicate genetic exchange across clades, and ϕst values show no genetic differentiation between morphotypes at different locations. Taken together, our morphological and genetic results do not provide evidence for cryptic species in M. cavernosa, but indicate instead that this species has an unusually high degree of polymorphism over a wide geographic area and persisting for >25 million years (myr).     

NMR and CD studies on the conformation of a synthetic peptide containing epitopes of the human immunodeficiency virus 1 transmembrane protein gp41

CD and nmr characterizations are reported for the 23-mer peptide CMC3, corresponding to residues 577–599 of gp41, the transmembrane glycoprotein of the human immunodeficiency virus 1. Concentration, temperature, and pH dependencies of CD and nmr spectra are indicative of self-association with a consequent stabilization of secondary structural elements in water. The addition to the water solution of small amounts of trifluoroethanol induces a secondary structure, mostly due to the presence of helical elements. The amphipathic character of the helix and the presence of three hydrophobic 4/3 heptad repeats suggest that the peptide could be structured in a symmetric association of helices, such as in a coiled-coil structure. This behavior is discussed in terms of a possible role of this segment in the gp41 envelope oligomerization. © 1996 John Wiley & Sons, Inc.     

Automated detection and mapping of electrical activation when electrogram morphology is complex

BackgroundMapping of cardiac electrical activity can be difficult when electrogram morphology is complex. Complex morphology (multiple and changing deflections) causes activation maps to vary when constructed by different analysts, particularly at areas with spatially varying conduction pattern. An algorithm was developed to automatically detect electrogram activation time which is robust to complex morphology.MethodElectrograms, many of which were complex, were collected from 320 canine epicardial border zone sites in five experiments. A library of electrogram activation times were manually marked a priori by two expert analysts. Then an algorithm which combined correlation and error functions was used to compare each input electrogram to library electrogram patterns. The closest match of input to library electrogram was used to estimate activation time. Once activation times at 320 sites were determined, activation maps were automatically constructed on a computerized grid. The algorithm was validated by comparison with activation times determined by the analysts.ResultsThe mean difference between manual and automated marking of activation time in electrograms acquired during reentrant ventricular tachycardia was 2.1 ± 3.9 ms. The mean sensitivity and positive predictive value were 95.9% and 83.8% respectively. The computer-automated marking process was completed within a few seconds and was robust to fractionated electrograms. Measurement error was mostly attributable to 60 Hz noise, which can be rectified with filtering.ConclusionsThe automated algorithm is useful for rapid and accurate automatic marking of multichannel electrograms, some of which may be fractionated, as well as for real-time display of activation maps in clinical electrophysiology or research studies.     

Herbivores modify selection on plant functional traits in a temperate rainforest understory

There is limited evidence regarding the adaptive value of plant functional traits in contrasting light environments. It has been suggested that changes in these traits in response to light availability can increase herbivore susceptibility. We tested the adaptive value of plant functional traits linked with carbon gain in contrasting light environments and also evaluated whether herbivores can modify selection on these traits in each light environment. In a temperate rainforest, we examined phenotypic selection on functional traits in seedlings of the pioneer tree Aristotelia chilensis growing in sun (canopy gap) and shade (forest understory) and subjected to either natural herbivory or herbivore exclusion. We found differential selection on functional traits depending on light environment. In sun, there was positive directional selection on photosynthetic rate and relative growth rate (RGR), indicating that selection favors competitive ability in a high-resource environment. Seedlings with high specific leaf area (SLA) and intermediate RGR were selected in shade, suggesting that light capture and conservative resource use are favored in the understory. Herbivores reduced the strength of positive directional selection acting on SLA in shade. We provide the first demonstration that natural herbivory rates can change the strength of selection on plant ecophysiological traits, that is, attributes whose main function is resource uptake. Research addressing the evolution of shade tolerance should incorporate the selective role of herbivores.     

Dengue and Zika virus capsid proteins bind to membranes and self-assemble into liquid droplets with nucleic acids

Dengue virus (DENV) and Zika virus (ZIKV) capsid proteins efficiently recruit and surround the viral RNA at the endoplasmic reticulum (ER) membrane to yield nascent viral particles. However, little is known either about the molecular mechanisms by which multiple copies of capsid proteins assemble into nucleocapsids (NCs) or how the NC is recruited and wrapped by the ER membrane during particle morphogenesis. Here, we measured relevant interactions concerning this viral process using purified DENV and ZIKV capsid proteins, membranes mimicking the ER lipid composition, and nucleic acids in in vitro conditions to understand the biophysical properties of the RNA genome encapsidation process. We found that both ZIKV and DENV capsid proteins bound to liposomes at liquid-disordered phase regions, docked exogenous membranes, and RNA molecules. Liquid–liquid phase separation is prone to occur when positively charged proteins interact with nucleic acids, which is indeed the case for the studied capsids. We characterized these liquid condensates by measuring nucleic acid partition constants and the extent of water dipolar relaxation, observing a cooperative process for the formation of the new phase that involves a distinct water organization. Our data support a new model in which capsid–RNA complexes directly bind the ER membrane, seeding the process of RNA recruitment for viral particle assembly. These results contribute to our understanding of the viral NC formation as a stable liquid–liquid phase transition, which could be relevant for dengue and Zika gemmation, opening new avenues for antiviral intervention.