Spring Conference 2011 - Society for General Microbiology

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Please note: Abstracts are published as received from the authors and are not subject to editing. 29 Spring Meeting 11–14 April 2011 Harrogate – www.sgmharrogate2011.org.uk SESSION AbSTrACTS ↑Contents HA05 Cont. when all mice were infected with iAV, and was prevented when an iAV-neutralizing antibody was used to inhibit iAV-replication in either index mice or contact mice. Together, these data provide novel insights into pneumococcal-influenza synergism and may indicate a previously unappreciated role of iAV in the spread of S. pneumoniae. Offered paper Suilysin contributes to invasion of Streptococcus suis in epithelial cells MArEN SEiTZ1 , Marcus Fulde1 , ralf Gerhard2 , Manfred rohde3 , Christoph G. Baums1 , ralph Goethe1 , Peter Valentin-Weigand 1 1 2 3 University of Veterinary Medicine Hannover, Hannover, Germany; Hannover Medical School, Hannover, Germany; Helmholtz Centre for Infection Research, Braunschweig, Germany Suilysin (SlY) is a cholesterol-dependent pore forming cytolysin secreted by Streptococcus suis (S. suis), an important swine and zoonotic pathogen. The role of SlY in S. suis host-cell interaction is still unclear. invasion assays showed a higher invasion-rate of a sly-positive strain in comparison with a sly-negative mutant. Electron microscopy analysis of the invasion process revealed formation of membrane ruffles. Therefore, we hypothesized that activation of the actin cytoskeleton and rho-GTPases are involved in SlY-mediated invasion process. To resolve the molecular mechanism of SlY host-cell interaction a point mutation was introduced in the tryptophane-rich motif of the conserved undecapeptide of SlY, which might be responsible for the pore-forming function. The mutated SlY had a reduced haemolytic and cytotoxic activity. The role of rho-GTPases was investigated by pull-down analysis of activated GTPases and colocalization-studies. Pull-down assays demonstrated a time-dependent activation of rac1 via both wild-type and mutated SlY. in accordance, colocalization experiments showed associated of SlY with F-actin and rac1. These results suggest that SlY is able to activate GTPases, independent of pore-formation, which is associated with the formation of membrane ruffles and internalization of S. suis. Offered paper CcpA-dependent capsule expression affects virulence of Streptococcus suis JOErG WillENBOrG1 , Marcus Fulde2 , Astrid de Greeff3 , Manfred rohde2 , Hilde Smith3 , Peter Valentin-Weigand 1 , ralph Goethe1 1 2 University of Veterinary Medicine, Hannover, Germany; Helmholtz Center for Infection Research, Braunschweig, Germany; 3Wageningen UR, Animal Sciences Group, Lelystad, Netherlands Streptococcus suis is one of the most important pathogens in pigs and an emerging zoonotic agent. Since the host environment seems to be an important regulatory component for virulence, we related expression of virulence determinants of Streptococcus suis to glucose availability during growth and to the catabolite control protein A (CcpA). We found that expression of the virulence-associated genes arcB, representing arcABC-operon expression, cps2A, representing capsular locus expression, as well as sly, ofs, sao, and epf differed significantly between early exponential (high glucose) to early stationary (low glucose) growth of a highly virulent serotype 2 strain. Deletion of ccpA altered expression of the surface located virulence-associated factors arcB, sao, eno as well as the two presently proven virulence factors in pigs, ofs and cps2A, at early exponential growth. A cDNA expression array revealed 259 differentially expressed genes in strain 10ΔccpA. Among the lower expressed genes 18 could be related to capsule biosynthesis. Correspondingly, electron microscopical characterization of strain 10ΔccpA revealed a markedly reduced thickness of the capsule. This phenotype correlated with a reduced resistance against killing by porcine neutrophils. Taken together, our data demonstrate that CcpA has a significant effect on capsule synthesis and virulence properties of Streptococcus suis. Group b streptococcal pili hijack integrin machinery to promote the development of meningitis Kelly S. Doran Dept of Biology, San Diego State University, Center for Microbial Sciences, San Diego State University, San Diego, CA, USA Group B Streptococcus (GBS) is the leading cause of meningitis in newborn infants. Bacterial cell surface appendages known as Pili have been recently described in Gram-positive streptococcal pathogens, including GBS. The pilin adhesin, PilA, located at the tip of the pilus, contributes to GBS adherence to blood-brain barrier (BBB) endothelium; however, the identity of the host receptor and the contribution of PilA in disease pathogenesis are largely unknown. using microarray analysis, defined bacterial mutants, recombinant PilA protein as well as in vivo neutrophil chemotaxis assays we demonstrated that PilA is both necessary and sufficient to activate host chemokine expression and drive neutrophil recruitment during infection. We further demonstrate that PilA binds collagen, which promotes GBS interaction with the α β integrin expressed on BBB endothelium. Both bacterial internalization and proinflammatory cytokine release were dependent upon 2 1 functional focal adhesin kinase. These findings were further substantiated in a murine model of hematogenous meningitis; mice infected with the PilA-deficient mutant exhibited delayed mortality, decreased neutrophil infiltration and bacterial CNS dissemination. Our results suggest that the bacterial pilus, specifically the PilA adhesin, plays a dual role in immune activation and bacterial entry into the CNS, and may represent an attractive target for therapeutic intervention. s o c i e t y f o r g e n e r a l Microbiology
Please note: Abstracts are published as received from the authors and are not subject to editing. 30 Spring Meeting 11–14 April 2011 Harrogate – www.sgmharrogate2011.org.uk SESSION AbSTrACTS ↑Contents HA05 Cont. Capsule biosynthesis in the pneumococcus Birgitta Henriques Norrmark Karolinska Institutet Pneumococci are major contributors to morbidity and mortality worldwide. They are the major cause of milder respiratory tract infections such as otitis and sinusitis, but also major contributors to severe diseases such as pneumonia, septicemia and meningitis. Several pneumococcal virulence attributes have been identified affecting disease development. Here important pneumococcal virulence components including pathogenicity islets will be discussed as well as interactions with the host. Offered paper Comparison of human parechovirus and enterovirus detection frequencies in cerebrospinal fluid samples collected over a 5-year period in Edinburgh HEli HArVAlA1,2 , Nigel Mcleish2 , Jasmina Kondracka2 , Chloe l. Mcintyre2 , E. Carol McWilliam leitch22 , Jeroen Witteveldt2 , Kate Templeton1 , Peter Simmonds1 1 2 Clinical Virology Centre, Edinburgh; University of Edinburgh, Edinburgh Human enteroviruses (EVs) and more recently parechoviruses (HPeVs) have been identified as the principal viral causes of meningitis and neonatal sepsis-like disease. We determined the relative frequencies of EV and HPeV types over a 5-year period in Edinburgh. Highly sensitive EV and HPeV PCr screening of 4168 uncultured cerebrospinal fluid (CSF) specimens from hospitalised individuals collected between 2005–2010 identified 201 EV and 31 HPeV positive samples. Most of those available could be directly typed by sequencing of VP1 (97%, 176/182). Highest frequencies of EV infections occurred in young adults (n=43; 8.6%) although a remarkably high proportion of positive samples (n=98; 46%) were obtained from young infants (
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