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ABSTRACT: Neisseria meningitidis (Nm) is a leading cause of bacterial meningitis and sepsis. Crucial virulence determinants of pathogenic Nm strains are the polysaccharide capsules that support invasion by hindering complement attack. In NmW-135 and NmY the capsules are built from the repeating units [→6)-α-D-Gal-(1→4)-α-Neu5Ac (2→]n and [→6)-α-D-Glc-(1→4)-α-Neu5Ac (2→]n, respectively. These unusual heteropolymers represent unique examples of a conjugation between sialic acid and hexosyl-sugars in a polymer chain. Moreover, despite the various catalytic strategies needed for sialic acid and hexose transfer, single enzymes (SiaDW-135/Y) have been identified to form these heteropolymers. Here we used SiaDW-135 as a model system to delineate structure-function relationships. In size exclusion chromatography active SiaDW-135 migrated as a monomer. Fold recognition programs suggested two separate glycosyltransferase domains, both containing a GT-B fold. Based on conserved motifs predicted folds could be classified as a hexosyl- and sialyl-transferase. To analyse enzyme properties and interplay of the two identified glycosyltransferase domains, saturation transfer difference NMR and mutational studies were carried out. Simultaneous and independent binding of UDP-Gal and CMP-Sia was seen in the absence of an acceptor as well as when the catalytic cycle was allowed to proceed. Enzyme variants with only one functionality were generated by site directed mutagenesis and shown to complement each other in trans when combined in an in vitro test system. Together the data strongly suggests that SiaDW-135 has evolved by fusion of two independent ancestral genes encoding a sialyl- and a galactosyltransferase activity.
Journal of Biological Chemistry 02/2013; · 4.77 Impact Factor
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Ulrich Vogel,
Muhamed-Kheir Taha,
Julio A Vazquez,
Jamie Findlow, Heike Claus,
Paola Stefanelli,
Dominique A Caugant,
Paula Kriz,
Raquel Abad,
Stefania Bambini, [......],
Maria Stella,
Danielle Thompson,
Mariagrazia Pizza,
Rino Rappuoli,
Davide Serruto,
Maurizio Comanducci,
Giuseppe Boccadifuoco,
John J Donnelly,
Duccio Medini,
Ray Borrow
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ABSTRACT: BACKGROUND: A novel multicomponent vaccine against meningococcal capsular group B (MenB) disease contains four major components: factor-H-binding protein, neisserial heparin binding antigen, neisserial adhesin A, and outer-membrane vesicles derived from the strain NZ98/254. Because the public health effect of the vaccine, 4CMenB (Novartis Vaccines and Diagnostics, Siena, Italy), is unclear, we assessed the predicted strain coverage in Europe. METHODS: We assessed invasive MenB strains isolated mainly in the most recent full epidemiological year in England and Wales, France, Germany, Italy, and Norway. Meningococcal antigen typing system (MATS) results were linked to multilocus sequence typing and antigen sequence data. To investigate whether generalisation of coverage applied to the rest of Europe, we also assessed isolates from the Czech Republic and Spain. FINDINGS: 1052 strains collected from July, 2007, to June, 2008, were assessed from England and Wales, France, Germany, Italy, and Norway. All MenB strains contained at least one gene encoding a major antigen in the vaccine. MATS predicted that 78% of all MenB strains would be killed by postvaccination sera (95% CI 63-90, range of point estimates 73-87% in individual country panels). Half of all strains and 64% of covered strains could be targeted by bactericidal antibodies against more than one vaccine antigen. Results for the 108 isolates from the Czech Republic and 300 from Spain were consistent with those for the other countries. INTERPRETATION: MATS analysis showed that a multicomponent vaccine could protect against a substantial proportion of invasive MenB strains isolated in Europe. Monitoring of antigen expression, however, will be needed in the future. FUNDING: Novartis Vaccines and Diagnostics.
The Lancet Infectious Diseases 02/2013; · 17.39 Impact Factor
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ABSTRACT: Zinc is a bivalent cation essential for bacterial growth and metabolism. The human pathogen Neisseria meningitidis expresses a homologue of the Zinc uptake regulator Zur which has been postulated to repress the putative zinc uptake protein ZnuD. In this study we elucidated the transcriptome of meningococci in response to zinc by microarrays and qRT-PCR. We identified 15 genes that were repressed upon zinc addition, and two genes that were activated. All transcription units (genes and operons) harbored a putative Zur binding motif in their promoter regions. A meningococcal Zur binding consensus motif (Zur box) was deduced in silico, which harbors a conserved central palindrome consisting of hexameric inverted repeats separated by three nucleotides (TGTTATDNHATAACA). In vitro binding of recombinant meningococcal Zur to this Zur box was shown for the first time using electrophoretic mobility shift assays. Zur binding to DNA depended specifically on the presence of zinc and was sensitive to mutations in the palindromic sequence. The Zur regulon among genes of unknown function comprised genes involved in zinc uptake, tRNA modification, and ribosomal assembly. In summary, this is the first study of the transcriptional response to zinc in meningococci.
Journal of bacteriology 10/2012; · 3.94 Impact Factor
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ABSTRACT: Neisseria meningitidis employs polysaccharides and outer membrane proteins to cope with human serum complement attack. To screen for factors influencing serum resistance, an assay was developed based on a colorimetric serum bactericidal assay. The screening used a genetically modified sequence type (ST)-41/44 clonal complex (cc) strain lacking LPS sialylation, polysaccharide capsule, the factor H binding protein (fHbp) and MutS, a protein of the DNA repair mechanism. After killing of .99.9% of the bacterial cells by serum treatment, the colorimetric assay was used to screen 1000 colonies, of which 35 showed enhanced serum resistance. Three mutant classes were identified. In the first class of mutants, enhanced expression of Opc was identified. Opc expression was associated with vitronectin binding and reduced membrane attack complex deposition confirming recent observations. Lipopolysaccharide (LPS) immunotype switch from immunotype L3 to L8/L1 by lgtA and lgtC phase variation represented the second class. Isogenic mutant analysis demonstrated that in ST-41/44 cc strains the L8/L1 immunotype was more serum resistant than the L3 immunotype. Consecutive analysis revealed that the immunotypes L8 and L1 were frequently observed in ST-41/44 cc isolates from both carriage and disease. Immunotype switch to L8/L1 is therefore suggested to contribute to the adaptive capacity of this meningococcal lineage. The third mutant class displayed a pilE allelic exchange associated with enhanced autoaggregation. The mutation of the C terminal hypervariable region D of PilE included a residue previously associated with increased pilus bundle formation. We suggest that autoaggregation reduced the surface area accessible to serum complement and protected from killing. The study highlights the ability of meningococci to adapt to environmental stress by phase variation and intrachromosomal recombination affecting subcapsular antigens. Copyright: ß 2012 Hubert et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The project was funded by grants to U.V. (from the Federal Ministry of Education and Research, reference number 0315434) and S.M. (from the Academy of Finland) within the 2nd joint call on PathoGenoMics of the EraNet (project No 10). Website: http://www.pathogenomics-era.net/2ndJointCall/. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist.
PLoS ONE 09/2012; 7(9). · 4.09 Impact Factor
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Brian D Plikaytis,
Maria Stella,
Giuseppe Boccadifuoco,
Lisa M Detora,
Mauro Agnusdei,
Laura Santini,
Brunella Brunelli,
Luca Orlandi,
Isabella Simmini,
Marzia Giuliani, [......],
Jan Oksnes,
Elisabeth Fritzsønn,
Anne-Marie Klem,
Dominique A Caugant,
Raquel Abad,
Julio A Vázquez,
Rino Rappuoli,
Mariagrazia Pizza,
John J Donnelly,
Duccio Medini
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ABSTRACT: The meningococcal antigen typing system (MATS) sandwich enzyme-linked immunosorbent assay (ELISA) was designed to measure the immunologic cross-reactivity and quantity of antigens in target strains of a pathogen. It was first used to measure the factor H-binding protein (fHbp), neisserial adhesin A (NadA), and neisserial heparin-binding antigen (NHBA) content of serogroup B meningococcal (MenB) isolates relative to a reference strain, or "relative potency" (RP). With the PorA genotype, the RPs were then used to assess strain coverage by 4CMenB, a multicomponent MenB vaccine. In preliminary studies, MATS accurately predicted killing in the serum bactericidal assay using human complement, an accepted correlate of protection for meningococcal vaccines. A study across seven laboratories assessed the reproducibility of RPs for fHbp, NadA, and NHBA and established qualification parameters for new laboratories. RPs were determined in replicate for 17 MenB reference strains at laboratories A to G. The reproducibility of RPs among laboratories and against consensus values across laboratories was evaluated using a mixed-model analysis of variance. Interlaboratory agreement was very good; the Pearson correlation coefficients, coefficients of accuracy, and concordance correlation coefficients exceeded 99%. The summary measures of reproducibility, expressed as between-laboratory coefficients of variation, were 7.85% (fHbp), 16.51% (NadA), and 12.60% (NHBA). The overall within-laboratory measures of variation adjusted for strain and laboratory were 19.8% (fHbp), 28.8% (NHBA), and 38.3% (NadA). The MATS ELISA was successfully transferred to six laboratories, and a further laboratory was successfully qualified.
Clinical and vaccine immunology: CVI 08/2012; 19(10):1609-17. · 2.37 Impact Factor
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ABSTRACT: Current concepts of vaccines against serogroup B meningococci (MenB) are mainly based on genetically variable protein antigens. Vaccine efficacy studies for meningococcal disease in developed countries are hampered by the low incidence. Licensure must therefore exclusively rely on clinical trials and laboratory investigation of meningococcal strains. In contrast to capsule polysaccharide vaccines, serum bactericidal assays for technical reasons are limited in their practicability as the surrogate of protection provided by MenB vaccines. Therefore, assays are required for reliable laboratory based assessment of expression of those specific antigen variants that are predicted to be targeted by bactericidal antibodies elicited by the vaccine. The MATS ELISA (MATS, meningococcal antigen typing system) reported recently is an example for such an assay. The paper discusses the pre- and post-licensure application of MATS, the role of reference laboratories, concepts of sustained provision of the assay, external quality assessment, and laboratory twinning.
Vaccine 04/2012; 30 Suppl 2:B73-7. · 3.77 Impact Factor
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ABSTRACT: Neisseria meningitidis causes invasive meningococcal disease in infants, toddlers, and adolescents worldwide. DNA sequence-based typing, including multilocus sequence typing, analysis of genetic determinants of antibiotic resistance, and sequence typing of vaccine antigens, has become the standard for molecular epidemiology of the organism. However, PCR of multiple targets and consecutive Sanger sequencing provide logistic constraints to reference laboratories. Taking advantage of the recent development of benchtop next-generation sequencers (NGSs) and of BIGSdb, a database accommodating and analyzing genome sequence data, we therefore explored the feasibility and accuracy of Ion Torrent Personal Genome Machine (PGM) sequencing for genomic typing of meningococci. Three strains from a previous meningococcus serogroup B community outbreak were selected to compare conventional typing results with data generated by semiconductor chip-based sequencing. In addition, sequencing of the meningococcal type strain MC58 provided information about the general performance of the technology. The PGM technology generated sequence information for all target genes addressed. The results were 100% concordant with conventional typing results, with no further editing being necessary. In addition, the amount of typing information, i.e., nucleotides and target genes analyzed, could be substantially increased by the combined use of genome sequencing and BIGSdb compared to conventional methods. In the near future, affordable and fast benchtop NGS machines like the PGM might enable reference laboratories to switch to genomic typing on a routine basis. This will reduce workloads and rapidly provide information for laboratory surveillance, outbreak investigation, assessment of vaccine preventability, and antibiotic resistance gene monitoring.
Journal of clinical microbiology 03/2012; 50(6):1889-94. · 4.16 Impact Factor
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ABSTRACT: The investigational multicomponent meningococcus serogroup B vaccine (4CMenB) targets the antigenetically variable population of serogroup B meningococci. Forty-one strains of capsule null locus (cnl) meningococci, which are frequent among healthy carriers, were selected from nine sequence types (ST), which belong to four clonal complexes (cc), and three countries. They were antigen sequence typed and analyzed for antigen expression to predict whether these strains harbor the genes and express the four vaccine antigens of 4CMenB as measured by the meningococcal antigen typing system (MATS). The PorA variant used in the vaccine was not found. The nadA gene was absent in all but one strain, which did not express the antigen in vitro. Only strains of clonal complex ST-198 harbored a factor H binding protein (FHBP) allele of the cross-reactive variant 1 family which is included in the vaccine. All these strains expressed the antigen. Five variants of the Neisserial heparin binding antigen (NHBA) gene were identified. Expression of NHBA was observed in all strains with highest levels in ST-198 cc and ST-845. The data suggest a potential impact of 4CMenB immunization at least on cnl meningococci of the ST-198 cc and ST-845.
Vaccine 11/2011; 30(2):155-60. · 3.77 Impact Factor
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ABSTRACT: Sequencing of yet unknown Haemophilus influenzae serotype c (Hic) and d (Hid) capsule synthesis regions II revealed four (ccs1-4) and five (dcs1-5) open reading frames, respectively. The inferred gene functions were in line with capsular polysaccharide structures. One or more proteins encoded by the Hic capsule synthesis region II showed similarity to Actinobacillus pleuropneumoniae serotype 1 and Actinobacillus suis K1 enzymes. Orthologues to the complete operon were observed in Actinobacillus minor strain 202, where even the gene order was conserved. Furthermore, Ccs4 was related to the capsule O-acetyltransferase of Neisseria meningitidis serogroup W-135. For the Hid locus, similarities to Hie, Mannheimia haemolytica A1 and N. meningitidis serogroup A were identified and the succession of genes was similar in the different species. The resemblance of genes and gene organization found for Hic and Hid with other species suggested horizontal gene transfer during capsule evolution across the bacterial classes.
Research in Microbiology 06/2011; 162(5):483-7. · 2.76 Impact Factor
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Biju Joseph,
Roland F Schwarz,
Burkhard Linke,
Jochen Blom,
Anke Becker, Heike Claus,
Alexander Goesmann,
Matthias Frosch,
Tobias Müller,
Ulrich Vogel,
Christoph Schoen
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ABSTRACT: Neisseria meningitidis is a naturally transformable, facultative pathogen colonizing the human nasopharynx. Here, we analyze on a genome-wide level the impact of recombination on gene-complement diversity and virulence evolution in N. meningitidis. We combined comparative genome hybridization using microarrays (mCGH) and multilocus sequence typing (MLST) of 29 meningococcal isolates with computational comparison of a subset of seven meningococcal genome sequences.
We found that lateral gene transfer of minimal mobile elements as well as prophages are major forces shaping meningococcal population structure. Extensive gene content comparison revealed novel associations of virulence with genetic elements besides the recently discovered meningococcal disease associated (MDA) island. In particular, we identified an association of virulence with a recently described canonical genomic island termed IHT-E and a differential distribution of genes encoding RTX toxin- and two-partner secretion systems among hyperinvasive and non-hyperinvasive lineages. By computationally screening also the core genome for signs of recombination, we provided evidence that about 40% of the meningococcal core genes are affected by recombination primarily within metabolic genes as well as genes involved in DNA replication and repair. By comparison with the results of previous mCGH studies, our data indicated that genetic structuring as revealed by mCGH is stable over time and highly similar for isolates from different geographic origins.
Recombination comprising lateral transfer of entire genes as well as homologous intragenic recombination has a profound impact on meningococcal population structure and genome composition. Our data support the hypothesis that meningococcal virulence is polygenic in nature and that differences in metabolism might contribute to virulence.
PLoS ONE 01/2011; 6(4):e18441. · 4.09 Impact Factor
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ABSTRACT: Neisseria meningitidis is a commensal of the human nasopharynx occasionally causing invasive disease. In vitro biofilms have been employed to model meningococcal carriage. A proteomic analysis of meningococcal biofilms was conducted and metabolic changes related to oxygen and nutrient limitation and upregulation of proteins involved in ROS defense were observed. The upregulated MntC which protects against ROS was shown to be required for meningococcal biofilm formation, but not for planktonic growth. ROS-induced proteomic changes might train the biofilm to cope with immune effectors.
Proteomics 12/2010; 10(24):4512-21. · 4.43 Impact Factor
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ABSTRACT: A new PCR protocol for molecular typing of Haemophilus influenzae serotype e (Hie) was developed. To this end, the sequence of the cap region II of Hie strain ATCC8142 was identified, which was >99% identical to the recently published sequence of Hie isolate 274. The PCR using primer pair TTL63/TTL64 amplifies an internal 592-bp fragment of ecs4, an e-specific capsule synthesis gene, in 40 of 40 Hie strains. Of all non-Hie strains, there were no false positives. False-negative results of the PCR proposed by Falla et al. (1994) are explained by single nucleotide insertions in the primer sequences.
International journal of medical microbiology: IJMM 10/2010; 301(2):176-9. · 2.80 Impact Factor
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Biju Joseph,
Susanne Schneiker-Bekel,
Anja Schramm-Glück,
Jochen Blom, Heike Claus,
Burkhard Linke,
Roland F Schwarz,
Anke Becker,
Alexander Goesmann,
Matthias Frosch,
Christoph Schoen
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ABSTRACT: Neisseria meningitidis serogroup B strains are responsible for most meningococcal cases in the industrialized countries, and strains belonging to the clonal complex ST-41/44 are among the most prevalent serogroup B strains in carriage and disease. Here, we report the first genome and transcriptome comparison of a serogroup B carriage strain from the clonal complex ST-41/44 to the serogroup B disease strain MC58 from the clonal complex ST-32. Both genomes are highly colinear, with only three major genome rearrangements that are associated with the integration of mobile genetic elements. They further differ in about 10% of their gene content, with the highest variability in gene presence as well as gene sequence found for proteins involved in host cell interactions, including Opc, NadA, TonB-dependent receptors, RTX toxin, and two-partner secretion system proteins. Whereas housekeeping genes coding for metabolic functions were highly conserved, there were considerable differences in their expression pattern upon adhesion to human nasopharyngeal cells between both strains, including differences in energy metabolism and stress response. In line with these genomic and transcriptomic differences, both strains also showed marked differences in their in vitro infectivity and in serum resistance. Taken together, these data support the concept of a polygenic nature of meningococcal virulence comprising differences in the repertoire of adhesins as well as in the regulation of metabolic genes and suggest a prominent role for immune selection and genetic drift in shaping the meningococcal genome.
Journal of bacteriology 10/2010; 192(20):5363-77. · 3.94 Impact Factor
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Journal of clinical microbiology 09/2010; 48(9):3459-60. · 4.16 Impact Factor
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Muhamed-Kheir Taha,
Sara Thulin Hedberg,
Marek Szatanik,
Eva Hong,
Corinne Ruckly,
Raquel Abad,
Sophie Bertrand,
Francoise Carion, Heike Claus,
Alejandra Corso, [......],
Per Olcén,
Marina Pana,
Anna Skoczynska,
Cecilia Sorhouet Pereira,
Paola Stefanelli,
Georgina Tzanakaki,
Magnus Unemo,
Julio A Vázquez,
Ulrich Vogel,
Izabela Wasko
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ABSTRACT: Identification of clinical isolates of Neisseria meningitidis that are resistant to rifampin is important to avoid prophylaxis failure in contacts of patients, but it is hindered by the absence of a breakpoint for resistance, despite many efforts toward standardization. We examined a large number (n = 392) of clinical meningococcal isolates, spanning 25 years (1984 to 2009), that were collected in 11 European countries, Argentina, and the Central African Republic. The collection comprises all clinical isolates with MICs of > or = 0.25 mg/liter (n = 161) received by the national reference laboratories for meningococci in the participating countries. Representative isolates displaying rifampin MICs of < 0.25 mg/liter were also examined (n = 231). Typing of isolates was performed, and a 660-bp DNA fragment of the rpoB gene was sequenced. Sequences differing by at least one nucleotide were defined as unique rpoB alleles. The geometric mean of the MICs was calculated for isolates displaying the same allele. The clinical isolates displaying rifampin MICs of > 1 mg/liter possessed rpoB alleles with nonsynonymous mutations at four critical amino acid residues, D542, H552, S548, and S557, that were absent in the alleles found in all isolates with MICs of < or = 1 mg/liter. Rifampin-susceptible isolates could be defined as those with MICs of < or = 1 mg/liter. The rpoB allele sequence and isolate data have been incorporated into the PubMLST Neisseria database (http://pubmlst.org/neisseria/). The rifampin-resistant isolates belonged to diverse genetic lineages and were associated with lower levels of bacteremia and inflammatory cytokines in mice. This biological cost may explain the lack of clonal expansion of these isolates.
Antimicrobial Agents and Chemotherapy 09/2010; 54(9):3651-8. · 4.84 Impact Factor
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ABSTRACT: A total of 489 clinical isolates of Pseudomonas aeruginosa was investigated for metallo-beta-lactamase (MBL) production. Molecular analysis detected a blaVIM-1 gene in the chromosome of one isolate and a blaVIM-2 gene carried on the plasmid in seven isolates. Moreover, we showed that an initial screening by combined susceptibility testing of imipenem and ceftazidime followed by a confirmatory EDTA combination disk test represents a valid alternative to the molecular investigation of MBL genes, making MBL detection possible in routine diagnostic laboratories.
Antimicrobial Agents and Chemotherapy 05/2010; 54(8):3493-7. · 4.84 Impact Factor
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ABSTRACT: Meningococcal disease is communicable by close contact or droplet aerosols. Striking features are high case fatality rates and peak incidences of invasive disease in infants, toddlers and adolescents. Vaccine development is hampered by bacterial immune evasion strategies including molecular mimicry.As for Haemophilus influenzae and Streptococcus pneumoniae, no vaccine has therefore been developed that targets all serogroups of Neisseria meningitidis. Polysaccharide vaccines available both in protein conjugated and non-conjugated form, have been introduced against capsular serogroups A, C,W-135 and Y, but are ineffective against serogroup B meningococci, which cause a significant burden of disease in many parts of the world. Detoxified outer membrane vesicles are used since decades to elicit protection against epidemic serogroup B disease. Genome mining and biochemical approaches have provided astounding progress recently in the identification of immunogenic, yet reasonably conserved outer membrane proteins. As subcapsular proteins nevertheless are unlikely to immunize against all serogroup B variants, thorough investigation by surrogate assays and molecular epidemiology approaches are needed prior to introduction and post-licensure of protein vaccines. Research currently addresses the analysis of life vaccines, meningococcus B polysaccharide modifications and mimotopes, as well as the use of N. lactamica outer membrane vesicles.
Microbial Biotechnology 05/2010; 4(1):20-31. · 2.53 Impact Factor
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ABSTRACT: Major pathogenic clonal complexes (cc) of Neisseria meningitidis differ substantially in their point prevalence among healthy carriers. We show that frequently carried pathogenic cc (e.g. sequence type ST-41/44 cc and ST-32 cc) depend on extracellular DNA (eDNA) to initiate in vitro biofilm formation, whereas biofilm formation of cc with low point prevalence (ST-8 cc and ST-11 cc) was eDNA-independent. For initial biofilm formation, a ST-32 cc type strain, but not a ST-11 type strain, utilized eDNA. The release of eDNA was mediated by lytic transglycosylase and cytoplasmic N-acetylmuramyl-L-alanine amidase genes. In late biofilms, outer membrane phospholipase A-dependent autolysis, which was observed in most cc, but not in ST-8 and ST-11 strains, was required for shear force resistance of microcolonies. Taken together, N. meningitidis evolved two different biofilm formation strategies, an eDNA-dependent one yielding shear force resistant microcolonies, and an eDNA-independent one. Based on the experimental findings and previous epidemiological observations, we hypothesize that most meningococcal cc display a settler phenotype, which is eDNA-dependent and results in a stable interaction with the host. On the contrary, spreaders (ST-11 and ST-8 cc) are unable to use eDNA for biofilm formation and might compensate for poor colonization properties by high transmission rates.
Molecular Microbiology 02/2010; 75(6):1355-71. · 5.01 Impact Factor
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Ines L Mordhorst, Heike Claus,
Christa Ewers,
Martin Lappann,
Christoph Schoen,
Johannes Elias,
Julia Batzilla,
Ulrich Dobrindt,
Lothar H Wieler,
Anne K Bergfeld,
Martina Mühlenhoff,
Ulrich Vogel
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ABSTRACT: Escherichia coli K1 causes disease in humans and birds. Its polysialic acid capsule can be O-acetylated via phase-variable expression of the acetyltransferase NeuO encoded by prophage CUS-3. The role of capsule O-acetylation in ecological adaptation or pathogenic invasion of E. coli K1 is largely unclear. A population genetics approach was performed to study the distribution of neuO among E. coli K1 isolates from human and avian sources. Multilocus sequence typing revealed 39 different sequence types (STs) among 183 E. coli K1 strains. The proportion of the ST95 complex (STC95) was 44%. NeuO was found in 98% of the STC95 strains, but only in 24% of other STs. Grouping of STs and prophage genotypes revealed a segregation of prophage types according to STs, suggesting coevolution of CUS-3 and the E. coli K1 host. Within the STC95, which is known to harbour both human and avian pathogenic isolates, CUS-3 genotypes were shared irrespective of the host species. Functional analysis of a variety of strain pairs revealed that NeuO-mediated K1 capsule O-acetylation enhanced desiccation resistance. In contrast, NeuO expression led to a reduced biofilm formation in biofilm positive E. coli K1 isolates. These findings suggest a delicate ecological balance of neuO'on'/'off' switching.
Environmental Microbiology 09/2009; 11(12):3154-65. · 5.84 Impact Factor
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ABSTRACT: Gram-positive, catalase-negative, chain-forming, coccus-shaped organisms were isolated both from intraperitoneally grown vesicles of the fox tapeworm Echinococcus multilocularis and the oropharynges of laboratory-kept Mongolian jirds (Meriones unguiculatus). The strains displayed no haemolytic activity on Columbia sheep blood agar, pyrrolidonyl arylamidase activity was negative and the organisms reacted weakly with Lancefield group D antiserum. On the basis of phenotypic characteristics, the strains were tentatively identified as members of the genus Streptococcus. Comparative 16S rRNA gene sequencing studies confirmed their assignment to the genus Streptococcus and revealed that Streptococcus hyointestinalis DSM 20770(T) was their closest phylogenetic neighbour (96.5 % sequence similarity). The levels of 16S rRNA gene sequence similarity between the isolates and representatives of species of the genus Streptococcus were only 95.7-96.2 %. On the basis of the phenotypic and molecular data presented, the isolates from Mongolian jirds represent a novel species of the genus Streptococcus, for which the name Streptococcus merionis sp. nov. is proposed. The type strain is WUE3771(T) (=DSM 19192(T)=CCUG 54871(T)).
International journal of systematic and evolutionary microbiology 05/2009; 59(Pt 4):766-70. · 2.27 Impact Factor
