Proximity, maps and conflict: New measures, New maps and New findings

This article introduces two new datasets. The first is a new interstate distance dataset. It is recognized that different theories regarding distance and conflict will call for different understandings of “distance” and accordingly, ten different types of distance measurement are presented. Moreover, it is argued that in order for a distance dataset to contain accurate distances, it is necessary for it to be based on maps reflecting state border changes over time. As such, a new map dataset is presented, including annualized maps for all states, stored in KML format. It will be shown that the frequent border changes experienced by states can have large impacts on distance calculations. The significance of the relationship between distance and conflict will be tested for the ten different types of distance measurement, not with the aim of finding a “best measure” but in order to demonstrate that distance remains an important variable and that each different form of distance measure can be significant

Genetic Dissection of an Exogenously Induced Biofilm in Laboratory and Clinical Isolates of E. coli

Microbial biofilms are a dominant feature of many human infections. However, developing effective strategies for controlling biofilms requires an understanding of the underlying biology well beyond what currently exists. Using a novel strategy, we have induced formation of a robust biofilm in Escherichia coli by utilizing an exogenous source of poly-N-acetylglucosamine (PNAG) polymer, a major virulence factor of many pathogens. Through microarray profiling of competitive selections, carried out in both transposon insertion and over-expression libraries, we have revealed the genetic basis of PNAG-based biofilm formation. Our observations reveal the dominance of electrostatic interactions between PNAG and surface structures such as lipopolysaccharides. We show that regulatory modulation of these surface structures has significant impact on biofilm formation behavior of the cell. Furthermore, the majority of clinical isolates which produced PNAG also showed the capacity to respond to the exogenously produced version of the polymer

RfaH Suppresses Small RNA MicA Inhibition of fimB Expression in Escherichia coli K-12

The phase variation (reversible on-off switching) of the type 1 fimbrial adhesin of Escherichia coli involves a DNA inversion catalyzed by FimB (switching in either direction) or FimE (on-to-off switching). Here, we demonstrate that RfaH activates expression of a FimB-LacZ protein fusion while having a modest inhibitory effect on a comparable fimB-lacZ operon construct and on a FimE-LacZ protein fusion, indicating that RfaH selectively controls fimB expression at the posttranscriptional level. Further work demonstrates that loss of RfaH enables small RNA (sRNA) MicA inhibition of fimB expression even in the absence of exogenous inducing stress. This effect is explained by induction of σE , and hence MicA, in the absence of RfaH. Additional work con- firms that the procaine-dependent induction of micA requires OmpR, as reported previously (A. Coornaert et al., Mol. Microbiol. 76:467–479, 2010, doi:10.1111/j.1365-2958.2010.07115.x), but also demonstrates that RfaH inhibition of fimB transcription is enhanced by procaine independently of OmpR. While the effect of procaine on fimB transcription is shown to be independent of RcsB, it was found to require SlyA, another known regulator of fimB transcription. These results demonstrate a complex role for RfaH as a regulator of fimB expression

Burkholderia cenocepacia BC2L-C Is a Super Lectin with Dual Specificity and Proinflammatory Activity

Lectins and adhesins are involved in bacterial adhesion to host tissues and mucus during early steps of infection. We report the characterization of BC2L-C, a soluble lectin from the opportunistic pathogen Burkholderia cenocepacia, which has two distinct domains with unique specificities and biological activities. The N-terminal domain is a novel TNF-α-like fucose-binding lectin, while the C-terminal part is similar to a superfamily of calcium-dependent bacterial lectins. The C-terminal domain displays specificity for mannose and l-glycero-d-manno-heptose. BC2L-C is therefore a superlectin that binds independently to mannose/heptose glycoconjugates and fucosylated human histo-blood group epitopes. The apo form of the C-terminal domain crystallized as a dimer, and calcium and mannose could be docked in the binding site. The whole lectin is hexameric and the overall structure, determined by electron microscopy and small angle X-ray scattering, reveals a flexible arrangement of three mannose/heptose-specific dimers flanked by two fucose-specific TNF-α-like trimers. We propose that BC2L-C binds to the bacterial surface in a mannose/heptose-dependent manner via the C-terminal domain. The TNF-α-like domain triggers IL-8 production in cultured airway epithelial cells in a carbohydrate-independent manner, and is therefore proposed to play a role in the dysregulated proinflammatory response observed in B. cenocepacia lung infections. The unique architecture of this newly recognized superlectin correlates with multiple functions including bacterial cell cross-linking, adhesion to human epithelia, and stimulation of inflammation

Drosophila melanogaster as a Model Host for the Burkholderia cepacia Complex

Colonization with bacterial species from the Burkholderia cepacia complex (Bcc) is associated with fast health decline among individuals with cystic fibrosis. In order to investigate the virulence of the Bcc, several alternative infection models have been developed. To this end, the fruit fly is increasingly used as surrogate host, and its validity to enhance our understanding of host-pathogen relationships has been demonstrated with a variety of microorganisms. Moreover, its relevance as a suitable alternative to mammalian hosts has been confirmed with vertebrate organisms.The aim of this study was to establish Drosophila melanogaster as a surrogate host for species from the Bcc. While the feeding method proved unsuccessful at killing the flies, the pricking technique did generate mortality within the populations. Results obtained with the fruit fly model are comparable with results obtained using mammalian infection models. Furthermore, validity of the Drosophila infection model was confirmed with B. cenocepacia K56-2 mutants known to be less virulent in murine hosts or in other alternative models. Competitive index (CI) analyses were also performed using the fruit fly as host. Results of CI experiments agree with those obtained with mammalian models.We conclude that Drosophila is a useful alternative infection model for Bcc and that fly pricking assays and competition indices are two complementary methods for virulence testing. Moreover, CI results indicate that this method is more sensitive than mortality tests

Defining Kawasaki disease and pediatric inflammatory multisystem syndrome-temporally associated to SARS-CoV-2 infection during SARS-CoV-2 epidemic in Italy: results from a national, multicenter survey

Background: There is mounting evidence on the existence of a Pediatric Inflammatory Multisystem Syndrome-temporally associated to SARS-CoV-2 infection (PIMS-TS), sharing similarities with Kawasaki Disease (KD). The main outcome of the study were to better characterize the clinical features and the treatment response of PIMS-TS and to explore its relationship with KD determining whether KD and PIMS are two distinct entities. Methods: The Rheumatology Study Group of the Italian Pediatric Society launched a survey to enroll patients diagnosed with KD (Kawasaki Disease Group - KDG) or KD-like (Kawacovid Group - KCG) disease between February 1st 2020, and May 31st 2020. Demographic, clinical, laboratory data, treatment information, and patients' outcome were collected in an online anonymized database (RedCAP®). Relationship between clinical presentation and SARS-CoV-2 infection was also taken into account. Moreover, clinical characteristics of KDG during SARS-CoV-2 epidemic (KDG-CoV2) were compared to Kawasaki Disease patients (KDG-Historical) seen in three different Italian tertiary pediatric hospitals (Institute for Maternal and Child Health, IRCCS "Burlo Garofolo", Trieste; AOU Meyer, Florence; IRCCS Istituto Giannina Gaslini, Genoa) from January 1st 2000 to December 31st 2019. Chi square test or exact Fisher test and non-parametric Wilcoxon Mann-Whitney test were used to study differences between two groups. Results: One-hundred-forty-nine cases were enrolled, (96 KDG and 53 KCG). KCG children were significantly older and presented more frequently from gastrointestinal and respiratory involvement. Cardiac involvement was more common in KCG, with 60,4% of patients with myocarditis. 37,8% of patients among KCG presented hypotension/non-cardiogenic shock. Coronary artery abnormalities (CAA) were more common in the KDG. The risk of ICU admission were higher in KCG. Lymphopenia, higher CRP levels, elevated ferritin and troponin-T characterized KCG. KDG received more frequently immunoglobulins (IVIG) and acetylsalicylic acid (ASA) (81,3% vs 66%; p = 0.04 and 71,9% vs 43,4%; p = 0.001 respectively) as KCG more often received glucocorticoids (56,6% vs 14,6%; p < 0.0001). SARS-CoV-2 assay more often resulted positive in KCG than in KDG (75,5% vs 20%; p < 0.0001). Short-term follow data showed minor complications. Comparing KDG with a KD-Historical Italian cohort (598 patients), no statistical difference was found in terms of clinical manifestations and laboratory data. Conclusion: Our study suggests that SARS-CoV-2 infection might determine two distinct inflammatory diseases in children: KD and PIMS-TS. Older age at onset and clinical peculiarities like the occurrence of myocarditis characterize this multi-inflammatory syndrome. Our patients had an optimal response to treatments and a good outcome, with few complications and no deaths

Relatedness of O-specific lipopolysaccharide side chain genes from strains of Shigella boydii type 12 belonging to two clonal groups and from Escherichia coli O7:K1.

The O-specific lipopolysaccharide side chains of Escherichia coli O7 and Shigella boydii type 12 possess similar but not identical chemical structures. We investigated the genetic relatedness between the O-specific side chain genes in members of these two species. Examination of outer membrane protein and lipopolysaccharide (LPS) banding patterns demonstrated that five strains which had been identified as S. boydii type 12 fell into two clonal groups, SB1 and SB2. Hybridizations with O7-specific radiolabeled probes derived from the chromosomal DNA of an E. coli O7 strain detected identical fragments among the three SB1 strains of S. boydii type 12 and the two E. coli O7 reference isolates. The two other S. boydii type 12 strains, which belonged to the SB2 clone, did not show homologies with the O7 probe under high-stringency conditions of hybridization. The homology between the O7 and type 12 LPS gene regions from the SB1 strains was further confirmed by the construction of O-specific side chain-deficient mutations in these strains by homologous recombination of a suicide plasmid containing O7-specific DNA sequences. Immunoblot experiments with O7 antiserum gave a weak cross-reaction with LPS purified from the SB2 strains but a very strong cross-reaction with the LPS from SB1 isolates. Antiserum raised to one of the SB2 strains cross-reacted only with S. boydii type 12 LPS from the SB1 clone but failed to react with O7 LPS

Identification, expression, and DNA sequence of the GDP-mannose biosynthesis genes encoded by the O7 rfb gene cluster of strain VW187 (Escherichia coli O7:K1).

The O7-specific lipopolysaccharide (LPS) in strains of Escherichia coli consists of a repeating unit made of galactose, mannose, rhamnose, 4-acetamido-2,6-dideoxyglucose, and N-acetylglucosamine. We have recently cloned and characterized genetically the O7-specific LPS biosynthesis region (rfbEcO7) of the E. coli O7:K1 strain VW187 (C. L. Marolda, J. Welsh, L. Dafoe, and M. A. Valvano, J. Bacteriol. 172:3590-3599, 1990). In this study, we localized the gnd gene encoding gluconate-6-phosphate dehydrogenase at one end of the rfbEcO7 gene cluster and sequenced that end of the cluster. Three open reading frames (ORF) encoding polypeptides of 275, 464, and 453 amino acids were identified upstream of gndEcO7, all transcribed toward the gnd gene. ORF275 had 45% similarity at the protein level with ORF16.5, which occupies a similar position in the Salmonella enterica LT2 rfb region, and presumably encodes a nucleotide sugar transferase. The polypeptides encoded by ORFs 464 and 453 were expressed under the control of the ptac promoter and visualized in Coomassie blue-stained sodium dodecyl sulfate-polyacrylamide gels and by maxicell analysis. ORF464 expressed GDP-mannose pyrophosphorylase and ORF453 encoded a phosphomannomutase, the enzymes for the biosynthesis pathway of GDP-mannose, one of the nucleotide sugar precursors for the formation of the O7 repeating unit. They were designated rfbMEcO7 and rfbKEcO7, respectively. The RfbMEcO7 polypeptide was homologous to the corresponding protein in S. enterica LT2, XanB of Xanthomonas campestris, and AlgA of Pseudomonas aeruginosa, all GDP-mannose pyrophosphorylases. RfbKEcO7 was very similar to CpsG of S. enterica LT2, an enzyme presumably involved in the biosynthesis of the capsular polysaccharide colanic acid, but quite different from the corresponding RfbK protein of S. enterica LT2