Publications by authors named "Charlene M Kahler"

46 Publications

Anti-Virulence Therapeutic Approaches for .

Antibiotics (Basel) 2021 Jan 21;10(2). Epub 2021 Jan 21.

Marshall Centre for Infectious Disease Research and Training, School of Biomedical Sciences, University of Western Australia, Crawley, WA 6009, Australia.

While antimicrobial resistance (AMR) is seen in both and , the former has become resistant to commonly available over-the-counter antibiotic treatments. It is imperative then to develop new therapies that combat current AMR isolates whilst also circumventing the pathways leading to the development of AMR. This review highlights the growing research interest in developing anti-virulence therapies (AVTs) which are directed towards inhibiting virulence factors to prevent infection. By targeting virulence factors that are not essential for gonococcal survival, it is hypothesized that this will impart a smaller selective pressure for the emergence of resistance in the pathogen and in the microbiome, thus avoiding AMR development to the anti-infective. This review summates the current basis of numerous anti-virulence strategies being explored for .
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http://dx.doi.org/10.3390/antibiotics10020103DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7911339PMC
January 2021

The Goldilocks Zone: Searching for a Phylogenetic Approach for the Recombinogenic Neisseria gonorrhoeae.

J Infect Dis 2020 11;222(11):1762-1763

The Marshall Center for Infectious Diseases Research and Training, Division of Infection and Immunity, School of Biomedical Sciences, University of Western Australia, Nedlands, Australia.

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http://dx.doi.org/10.1093/infdis/jiaa079DOI Listing
November 2020

Meningococcal Disease-Associated Prophage-Like Elements Are Present in Neisseria gonorrhoeae and Some Commensal Neisseria Species.

Genome Biol Evol 2020 02;12(2):3938-3950

The Marshall Centre for Infectious Diseases Research and Training, The University of Western Australia, Crawley, Australia.

Neisseria spp. possess four genogroups of filamentous prophages, termed Nf1 to 4. A filamentous bacteriophage from the Nf1 genogroup termed meningococcal disease-associated phage (MDA φ) is associated with clonal complexes of Neisseria meningitidis that cause invasive meningococcal disease. Recently, we recovered an isolate of Neisseria gonorrhoeae (ExNg63) from a rare case of gonococcal meningitis, and found that it possessed a region with 90% similarity to Nf1 prophages, specifically, the meningococcal MDA φ. This led to the hypothesis that the Nf1 prophage may be more widely distributed amongst the genus Neisseria. An analysis of 92 reference genomes revealed the presence of intact Nf1 prophages in the commensal species, Neisseria lactamica and Neisseria cinerea in addition to the pathogen N. gonorrhoeae. In N. gonorrhoeae, Nf1 prophages had a restricted distribution but were present in all representatives of MLST ST1918. Of the 160 phage integration sites identified, only one common insertion site was found between one isolate of N. gonorrhoeae and N. meningitidis. There was an absence of any obvious conservation of the receptor for prophage entry, PilE, suggesting that the phage may have been obtained by natural transformation. An examination of the restriction modification systems and mutated mismatch repair systems with prophage presence suggested that there was no obvious preference for these hosts. A timed phylogeny inferred that N. meningitidis was the donor of the Nf1 prophages in N. lactamica and N. gonorrhoeae. Further work is required to determine whether Nf1 prophages are active and can act as accessory colonization factors in these species.
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http://dx.doi.org/10.1093/gbe/evaa023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7058167PMC
February 2020

Meningococcal B Vaccine and Meningococcal Carriage in Adolescents in Australia.

N Engl J Med 2020 01;382(4):318-327

From the Vaccinology and Immunology Research Trials Unit, Women's and Children's Health Network (H.S.M.), the Robinson Research Institute and Adelaide Medical School (H.S.M., M.M.), and the School of Public Health (T.R.S.), University of Adelaide, the Communicable Disease Control Branch, SA Health (A.P.K.), and SA Pathology (A.L.), Adelaide, and the Marshall Centre for Infectious Disease Research and Training, School of Biomedical Science (C.M.K.), and the School of Medicine (P.R.), University of Western Australia, the Departments of General Paediatrics and Immunology, Perth Children's Hospital (P.R.), and Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kid's Institute (P.R.), Perth - all in Australia; the Department of Zoology, University of Oxford, Oxford (J.M.M., M.C.J.M.), the Immunization Department, Public Health England, London (S.N.L., M.E.R., C.T.), the Departments of Pathology and Veterinary Medicine, University of Cambridge, Cambridge (C.T.), the Meningococcal Reference Unit, Public Health England, Manchester (R.B.), and Bristol Children's Vaccine Centre, Schools of Cellular and Molecular Medicine and of Population Health Sciences, University of Bristol, Bristol (A.F.) - all in the United Kingdom; GlaxoSmithKline Vaccines, Amsterdam (J.W.); and GlaxoSmithKline Vaccines, Rockville, MD (K.V.).

Background: The meningococcal group B vaccine 4CMenB is a new, recombinant protein-based vaccine that is licensed to protect against invasive group B meningococcal disease. However, its role in preventing transmission and, therefore, inducing population (herd) protection is uncertain.

Methods: We used cluster randomization to assign, according to school, students in years 10 to 12 (age, 15 to 18 years) in South Australia to receive 4CMenB vaccination either at baseline (intervention) or at 12 months (control). The primary outcome was oropharyngeal carriage of disease-causing (group A, B, C, W, X, or Y) in students in years 10 and 11, as identified by polymerase-chain-reaction assays for (encoding porin protein A) and genogroups. Secondary outcomes included carriage prevalence and acquisition of all and individual disease-causing genogroups. Risk factors for carriage were assessed at baseline.

Results: A total of 237 schools participated. During April through June 2017, a total of 24,269 students in years 10 and 11 and 10,220 students in year 12 were enrolled. At 12 months, there was no difference in the prevalence of carriage of disease-causing between the vaccination group (2.55%; 326 of 12,746) and the control group (2.52%; 291 of 11,523) (adjusted odds ratio, 1.02; 95% confidence interval [CI], 0.80 to 1.31; P = 0.85). There were no significant differences in the secondary carriage outcomes. At baseline, the risk factors for carriage of disease-causing included later year of schooling (adjusted odds ratio for year 12 vs. year 10, 2.75; 95% CI, 2.03 to 3.73), current upper respiratory tract infection (adjusted odds ratio, 1.35; 95% CI, 1.12 to 1.63), cigarette smoking (adjusted odds ratio, 1.91; 95% CI, 1.29 to 2.83), water-pipe smoking (adjusted odds ratio, 1.82; 95% CI, 1.30 to 2.54), attending pubs or clubs (adjusted odds ratio, 1.54; 95% CI, 1.28 to 1.86), and intimate kissing (adjusted odds ratio, 1.65; 95% CI, 1.33 to 2.05). No vaccine safety concerns were identified.

Conclusions: Among Australian adolescents, the 4CMenB vaccine had no discernible effect on the carriage of disease-causing meningococci, including group B. (Funded by GlaxoSmithKline; ClinicalTrials.gov number, NCT03089086.).
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http://dx.doi.org/10.1056/NEJMoa1900236DOI Listing
January 2020

Genomic characterisation of perinatal Western Australian Streptococcus agalactiae isolates.

PLoS One 2019 2;14(10):e0223256. Epub 2019 Oct 2.

The School of Medicine, Division of Obstetrics and Gynaecology, The University of Western Australia, Perth, Western Australia, Australia.

As a leading cause of neonatal sepsis, Streptococcus agalactiae, commonly known as Group B Streptococcus, is a major neonatal pathogen. Current global screening practices employ risk- or culture-based protocols for detection of these organisms. In Western Australia (WA), universal culture-based screening is provided, with subsequent intrapartum antibiotic prophylaxis for all S. agalactiae-positive women during labour. Widespread antibiotic exposure is not ideal and this is one of the factors driving development of vaccines against S. agalactiae. Vaccine candidates have focused on the capsule, surface proteins and pilus types, however, capsule serotypes are known to vary geographically. The aim of this study was to use genome sequencing to gain an understanding of the circulating genotypes in WA, and to assess variations in the associated gene pools. We sequenced 141 antenatal carriage (vaginal/rectal) isolates and 10 neonatal invasive disease isolates from WA. Based on the global PubMLST database, the 151 strains were characterised into 30 sequence types, with clustering of these mainly into clonal complexes 1, 12, 17, 19 and 23. Of the genes encoding eleven surface proteins that were analysed, the most prevalent were fbp, lmb and scpB which were present in ≥ 98% of isolates. A cluster of non-haemolytic isolates, one of which was a neonatal invasive disease isolate, appeared to lack the entire cyl locus. Admixture analysis of population structure revealed evidence of genetic transfer among the WA isolates across structural groups. When compared against the PubMLST S. agalactiae data, WA isolates showed high levels of strain diversity with minimal apparent clustering. This is the first whole genome sequence study of WA S. agalactiae isolates and also represents the first addition of Australian isolate data to PubMLST. This report provides insight into the distribution and diversity of vaccine targets of S. agalactiae within Western Australia, indicating that the most appropriate capsular vaccine for this population would be the proposed pentavalent (Cps Ia, Ib, II, III and V) preparation, whilst vaccines targeting surface proteins should ideally utilise Fbp, Lmb and/or ScpB.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0223256PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6774530PMC
March 2020

Peptidyl-Prolyl Isomerase Is Essential for Proteome Homeostasis and Virulence in Burkholderia pseudomallei.

Infect Immun 2019 10 19;87(10). Epub 2019 Sep 19.

Marshall Center for Infectious Diseases Research and Training, School of Biomedical Sciences, University of Western Australia, Perth, WA, Australia

is the causative agent of melioidosis, a disease endemic to Southeast Asia and northern Australia. Mortality rates in these areas are high even with antimicrobial treatment, and there are few options for effective therapy. Therefore, there is a need to identify antibacterial targets for the development of novel treatments. Cyclophilins are a family of highly conserved enzymes important in multiple cellular processes. Cyclophilins catalyze the isomerization of -proline bonds, a rate-limiting step in protein folding which has been shown to be important for bacterial virulence. carries a putative cyclophilin B gene, , the role of which was investigated. A () mutant strain demonstrates impaired biofilm formation and reduced motility. Macrophage invasion and survival assays showed that although the strain retained the ability to infect macrophages, it had reduced survival and lacked the ability to spread cell to cell, indicating is essential for virulence. This is reflected in the BALB/c mouse infection model, demonstrating the requirement of for disease dissemination and progression. Proteomic analysis demonstrates that the loss of PpiB leads to pleiotropic effects, supporting the role of PpiB in maintaining proteome homeostasis. The loss of PpiB leads to decreased abundance of multiple virulence determinants, including flagellar machinery and alterations in type VI secretion system proteins. In addition, the loss of leads to increased sensitivity toward multiple antibiotics, including meropenem and doxycycline, highlighting inhibition as a promising antivirulence target to both treat infections and increase antibiotic efficacy.
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http://dx.doi.org/10.1128/IAI.00528-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6759293PMC
October 2019

The Detroit 562 Pharyngeal Immortalized Cell Line Model for the Assessment of Infectivity of Pathogenic Neisseria sp.

Methods Mol Biol 2019 ;1969:123-133

Marshall Centre for Infectious Diseases Research and Training, School of Biomedical Sciences, University of Western Australia, Perth, WA, Australia.

Neisseria meningitidis and Neisseria gonorrhoeae are obligate pathogens of the human host. Due to their adaptation to the human host, many factors required for infection are specialized for the human host to the point that natural infection processes are difficult to replicate in animal models. Immortalized human cell lines have been used to identify the host factors necessary for successful colonization of human mucosal surfaces. One such model is the Detroit 562 pharyngeal immortalized cell monolayer model which is used to measure the rate of attachment to and invasion of N. meningitidis and N. gonorrhoeae into epithelial cells. The methodology of this assay, as well as the maintenance of Detroit 562 cells necessary for the experiment, will be described.
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http://dx.doi.org/10.1007/978-1-4939-9202-7_9DOI Listing
September 2019

Moraxella catarrhalis Restriction-Modification Systems Are Associated with Phylogenetic Lineage and Disease.

Genome Biol Evol 2018 11 1;10(11):2932-2946. Epub 2018 Nov 1.

Institute for Glycomics, Griffith University, Gold Coast, Queensland, Australia.

Moraxella catarrhalis is a human-adapted pathogen, and a major cause of otitis media (OM) and exacerbations of chronic obstructive pulmonary disease. The species is comprised of two main phylogenetic lineages, RB1 and RB2/3. Restriction-modification (R-M) systems are among the few lineage-associated genes identified in other bacterial genera and have multiple functions including defense against foreign invading DNA, maintenance of speciation, and epigenetic regulation of gene expression. Here, we define the repertoire of R-M systems in 51 publicly available M. catarrhalis genomes and report their distribution among M. catarrhalis phylogenetic lineages. An association with phylogenetic lineage (RB1 or RB2/3) was observed for six R-M systems, which may contribute to the evolution of the lineages by restricting DNA transformation. In addition, we observed a relationship between a mutually exclusive Type I R-M system and a Type III R-M system at a single locus conserved throughout a geographically and clinically diverse set of M. catarrhalis isolates. The Type III R-M system at this locus contains the phase-variable Type III DNA methyltransferase, modM, which controls a phasevarion (phase-variable regulon). We observed an association between modM presence and OM-associated middle ear isolates, indicating a potential role for ModM-mediated epigenetic regulation in OM pathobiology.
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http://dx.doi.org/10.1093/gbe/evy226DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6241649PMC
November 2018

Enzyme targets for drug design of new anti-virulence therapeutics.

Curr Opin Struct Biol 2018 12 14;53:140-150. Epub 2018 Sep 14.

School of Molecular Sciences, University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia; Marshall Centre for Infectious Disease Research and Training, School of Biomedical Sciences, University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia. Electronic address:

Society has benefitted greatly from the use of antibiotics. Unfortunately, the misuse of these valuable molecules has resulted in increased levels of antibiotic resistance, a major global and public health issue. This resistance and the reliance on a small number of biological targets for the development of antibiotics emphasizes the need for new targets. A critical aspect guiding the development of new antimicrobials through a rational structure-guided approach is to understand the molecular structures of specific biological targets of interest. Here we give an overview of the structures of bacterial virulence enzyme targets involved in protein folding, peptidoglycan biosynthesis and cell wall modification. These include enzymes of the thiol-disulphide oxidoreductase pathway (DSB enzymes), peptidyl-proly cis/trans isomerases (Mips), enzymes from the Mur pathway and enzymes involved in lipopolysaccharide modification (EptA and ArnT). We also present progress towards inhibitor design of these targets for the development of novel anti-virulence therapeutic agents.
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http://dx.doi.org/10.1016/j.sbi.2018.08.010DOI Listing
December 2018

Structure-Function Relationships of the Neisserial EptA Enzyme Responsible for Phosphoethanolamine Decoration of Lipid A: Rationale for Drug Targeting.

Front Microbiol 2018 21;9:1922. Epub 2018 Aug 21.

Department of Microbiology and Immunology, The Emory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, GA, United States.

Bacteria cause disease by two general mechanisms: the action of their toxins on host cells and induction of a pro-inflammatory response that can lead to a deleterious cytokine/chemokine response (e.g., the so-called cytokine storm) often seen in bacteremia/septicemia. These major mechanisms may overlap due to the action of surface structures that can have direct and indirect actions on phagocytic or non-phagocytic cells. In this respect, the lipid A (endotoxin) component of lipopolysaccharide (LPS) possessed by Gram-negative bacteria has been the subject of literally thousands of studies over the past century that clearly identified it as a key virulence factor in endotoxic shock. In addition to its capacity to modulate inflammatory responses, endotoxin can also modulate bacterial susceptibility to host antimicrobials, such as the host defense peptides termed cationic antimicrobial peptides. This review concentrates on the phosphoethanolamine (PEA) decoration of lipid A in the pathogenic species of the genus [ and ]. PEA decoration of lipid A is mediated by the enzyme EptA (formerly termed LptA) and promotes resistance to innate defense systems, induces the pro-inflammatory response and can influence the fitness of bacteria during infection. These important biological properties have driven efforts dealing with the biochemistry and structural biology of EptA that will facilitate the development of potential inhibitors that block PEA addition to lipid A.
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http://dx.doi.org/10.3389/fmicb.2018.01922DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6111236PMC
August 2018

Structural and biochemical insights into the disulfide reductase mechanism of DsbD, an essential enzyme for neisserial pathogens.

J Biol Chem 2018 10 4;293(43):16559-16571. Epub 2018 Sep 4.

From the Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3086, Victoria, Australia,

The worldwide incidence of neisserial infections, particularly gonococcal infections, is increasingly associated with antibiotic-resistant strains. In particular, extensively drug-resistant strains that are resistant to third-generation cephalosporins are a major public health concern. There is a pressing clinical need to identify new targets for the development of antibiotics effective against -specific processes. In this study, we report that the bacterial disulfide reductase DsbD is highly prevalent and conserved among spp. and that this enzyme is essential for survival of DsbD is a membrane-bound protein that consists of two periplasmic domains, n-DsbD and c-DsbD, which flank the transmembrane domain t-DsbD. In this work, we show that the two functionally essential periplasmic domains of DsbD catalyze electron transfer reactions through unidirectional interdomain interactions, from reduced c-DsbD to oxidized n-DsbD, and that this process is not dictated by their redox potentials. Structural characterization of the n- and c-DsbD domains in both redox states provides evidence that steric hindrance reduces interactions between the two periplasmic domains when n-DsbD is reduced, thereby preventing a futile redox cycle. Finally, we propose a conserved mechanism of electron transfer for DsbD and define the residues involved in domain-domain recognition. Inhibitors of the interaction of the two DsbD domains have the potential to be developed as anti-neisserial agents.
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http://dx.doi.org/10.1074/jbc.RA118.004847DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6204915PMC
October 2018

B Part of It protocol: a cluster randomised controlled trial to assess the impact of 4CMenB vaccine on pharyngeal carriage of in adolescents.

BMJ Open 2018 07 10;8(7):e020988. Epub 2018 Jul 10.

Vaccine Development, GlaxoSmithKline Vaccines, Siena, Italy.

Introduction: South Australia (SA) has the highest notification rate of invasive meningococcal disease in Australia with the majority of cases due to serogroup B. is carried in the pharynx, with adolescents having the highest rates of carriage. A vaccine designed to offer protection against serogroup B (4CMenB) is licensed in Australia. The SA MenB vaccine carriage study aims to assess the impact of 4CMenB on carriage of in adolescents.

Methods And Analysis: This is a parallel cluster randomised controlled trial enrolling year 10, 11 and 12 school students (approximately 16-18 years of age) throughout SA, in metropolitan and rural/remote areas. Schools are randomised to intervention (4CMenB vaccination at baseline) or control (4CMenB vaccination at study completion) with randomisation stratified by school size and socioeconomic status, as measured by the Index of Community Socio-Educational Advantage (Australian Curriculum). Oropharyngeal swabs will be taken from all students at visit 1, and 12 months later from year 11 and 12 students. Students unvaccinated in 2017 will receive vaccine at the 12-month follow-up. Carriage prevalence of will be determined by PCR at baseline and 12 months following 4CMenB vaccination and compared with carriage prevalence at 12 months in unvaccinated students. A questionnaire will be completed at baseline and 12 months to assess risk factors associated with carriage. The primary outcome of carriage prevalence of disease causing at 12 months will be compared between groups using logistic regression, with generalised estimating equations used to account for clustering at the school level. The difference in carriage prevalence between groups will be expressed as an OR with 95% CI.

Ethics And Dissemination: The study was approved by the Women's and Children's Health Network Human Research Ethics Committee (WCHN HREC). The protocol, informed consent forms, recruitment materials, social media and all participant materials have been reviewed and approved by the WCHN HREC and updated on ClinicalTrials.gov. Results will be published in international peer-reviewed journals and presented at national and international conferences. The study findings will be provided in public forums and to study participants and participating schools.

Trial Registration Number: ACTRN12617000079347. NCT03089086; Pre-results.
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http://dx.doi.org/10.1136/bmjopen-2017-020988DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6082482PMC
July 2018

Communication Ambassadors-an Australian Social Media Initiative to Develop Communication Skills in Early Career Scientists.

J Microbiol Biol Educ 2018 30;19(1). Epub 2018 Mar 30.

Department of Microbiology and Immunology, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, 3010, Australia.

Science communication is a skill set to be developed through ongoing interactions with different stakeholders across a variety of platforms. Opportunities to engage the general public are typically reserved for senior scientists, but the use of social media in science communication allows all scientists to instantaneously disseminate their findings and interact with online users. The Communication Ambassador program is a social media initiative launched by the Australian Society for Microbiology to expand the online presence and science communication portfolios of early-career scientists. Through their participation in the program, a rotating roster of Australian microbiologists have broadened the online reach of the Society's social media channels as well as their own professional networks by attending and live-tweeting microbiology events throughout the year. We present the Communication Ambassador program as a case study of coordinated social media activity in science communication to the general public, and describe the potential for its applications in science education and training.
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http://dx.doi.org/10.1128/jmbe.v19i1.1428DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969406PMC
March 2018

Multidrug-resistant Neisseria gonorrhoeae: future therapeutic options.

Future Microbiol 2018 04 8;13:499-501. Epub 2018 Mar 8.

Marshall Center for Infectious Diseases Research & Training, School of Biomedical Sciences, University of Western Australia, Australia.

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http://dx.doi.org/10.2217/fmb-2017-0258DOI Listing
April 2018

Genomic epidemiology and population structure of Neisseria gonorrhoeae from remote highly endemic Western Australian populations.

BMC Genomics 2018 02 27;19(1):165. Epub 2018 Feb 27.

The Marshall Centre for Infectious Diseases Research and Training, The University of Western Australia, Crawley, Australia.

Background: Neisseria gonorrhoeae causes gonorrhoea, the second most commonly notified sexually transmitted infection in Australia. One of the highest notification rates of gonorrhoea is found in the remote regions of Western Australia (WA). Unlike isolates from the major Australian population centres, the remote community isolates have low rates of antimicrobial resistance (AMR). Population structure and whole-genome comparison of 59 isolates from the Western Australian N. gonorrhoeae collection were used to investigate relatedness of isolates cultured in the metropolitan and remote areas. Core genome phylogeny, multilocus sequencing typing (MLST), N. gonorrhoeae multi-antigen sequence typing (NG-MAST) and N. gonorrhoeae sequence typing for antimicrobial resistance (NG-STAR) in addition to hierarchical clustering of sequences were used to characterize the isolates.

Results: Population structure analysis of the 59 isolates together with 72 isolates from an international collection, revealed six population groups suggesting that N. gonorrhoeae is a weakly clonal species. Two distinct population groups, Aus1 and Aus2, represented 63% of WA isolates and were mostly composed of the remote community isolates that carried no chromosomal AMR genotypes. In contrast, the Western Australian metropolitan isolates were frequently multi-drug resistant and belonged to population groups found in the international database, suggesting international transmission of the isolates.

Conclusions: Our study suggests that the population structure of N. gonorrhoeae is distinct between the communities in remote and metropolitan WA. Given the high rate of AMR in metropolitan regions, ongoing surveillance is essential to ensure the enduring efficacy of the empiric gonorrhoea treatment in remote WA.
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http://dx.doi.org/10.1186/s12864-018-4557-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6889462PMC
February 2018

Production, biophysical characterization and initial crystallization studies of the N- and C-terminal domains of DsbD, an essential enzyme in Neisseria meningitidis.

Acta Crystallogr F Struct Biol Commun 2018 01 1;74(Pt 1):31-38. Epub 2018 Jan 1.

Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria 3086, Australia.

The membrane protein DsbD is a reductase that acts as an electron hub, translocating reducing equivalents from cytoplasmic thioredoxin to a number of periplasmic substrates involved in oxidative protein folding, cytochrome c maturation and oxidative stress defence. DsbD is a multi-domain protein consisting of a transmembrane domain (t-DsbD) flanked by two periplasmic domains (n-DsbD and c-DsbD). Previous studies have shown that DsbD is required for the survival of the obligate human pathogen Neisseria meningitidis. To help understand the structural and functional aspects of N. meningitidis DsbD, the two periplasmic domains which are required for electron transfer are being studied. Here, the expression, purification and biophysical properties of n-NmDsbD and c-NmDsbD are described. The crystallization and crystallographic analysis of n-NmDsbD and c-NmDsbD are also described in both redox states, which differ only in the presence or absence of a disulfide bond but which crystallized in completely different conditions. Crystals of n-NmDsbD, n-NmDsbD, c-NmDsbD and c-NmDsbD diffracted to 2.3, 1.6, 2.3 and 1.7 Å resolution and belonged to space groups P23, P321, P4 and P121, respectively.
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http://dx.doi.org/10.1107/S2053230X17017800DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5947690PMC
January 2018

Differences in the population structure of Neisseria meningitidis in two Australian states: Victoria and Western Australia.

PLoS One 2017 24;12(10):e0186839. Epub 2017 Oct 24.

Marshall Center for Infectious Disease Research and Training, School of Biomedical Sciences, The University of Western Australia, Perth, Western Australia, Australia.

Neisseria meningitidis is the causative agent of invasive meningococcal disease (IMD). A recombinant vaccine called Bexsero® incorporates four subcapsular antigens (fHbp, NHBA, NadA and PorA) which are used to assign a Bexsero® antigen sequence type (BAST) to each meningococcal strain. The vaccine elicits an immune response against combinations of variants of these antigens which have been grouped into specific BAST profiles that have been shown to have different distributions within geographical locations thus potentially affecting the efficacy of the vaccine. In this study, invasive meningococcal disease isolates from the western seaboard of Australia (Western Australia; WA) were compared to those from the south-eastern seaboard (Victoria; VIC) from 2008 to 2012. Whole-genome sequencing (WGS) of 131 meningococci from VIC and 70 meningococci from WA were analysed for MLST, FetA and BAST profiling. Serogroup B predominated in both jurisdictions and a total of 10 MLST clonal complexes (cc) were shared by both states. Isolates belonging to cc22, cc103 and cc1157 were unique to VIC whilst isolates from cc60 and cc212 were unique to WA. Clonal complex 41/44 represented one-third of the meningococcal population in each state but the predominant ST was locally different: ST-6058 in VIC and ST-146 in WA. Of the 108 BAST profiles identified in this collection, only 9 BASTs were simultaneously observed in both states. A significantly larger proportion of isolates in VIC harboured alleles for the NHBA-2 peptide and fHbp-1, antigenic variants predicted to be covered by the Bexsero® vaccine. The estimate for vaccine coverage in WA (47.1% [95% CI: 41.1-53.1%]) was significantly lower than that in VIC (66.4% [95% CI: 62.3-70.5%]). In conclusion, the antigenic structure of meningococci causing invasive disease in two geographically distinct states of Australia differed significantly during the study period which may affect vaccine effectiveness and highlights the need for representative surveillance when predicting potential impact of meningococcal B vaccines.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0186839PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5655437PMC
November 2017

Clonal Expansion of New Penicillin-Resistant Clade of Neisseria meningitidis Serogroup W Clonal Complex 11, Australia.

Emerg Infect Dis 2017 08 15;23(8):1364-1367. Epub 2017 Aug 15.

In Western Australia, Neisseria meningitidis serogroup W clonal complex 11 became the predominant cause of invasive meningococcal disease in 2016. We used core-genome analysis to show emergence of a penicillin-resistant clade that had the penA_253 allele. This new penicillin-resistant clade might affect treatment regimens for this disease.
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http://dx.doi.org/10.3201/eid2308.170259DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5547816PMC
August 2017

Emergence of a Urogenital Pathotype of Neisseria meningitidis.

Trends Microbiol 2017 07 22;25(7):510-512. Epub 2017 May 22.

Marshall Center for Infectious Diseases Research and Training, School of Biomedical Sciences, University of Western Australia, Australia. Electronic address:

Neisseria meningitidis is the causative agent of transmissible sepsis and meningitis in humans. A urogenital pathotype of N. meningitidis as the causative agent of transmissible urethritis in the USA has been recently characterised. This pathotype belongs to clonal complex 11 and has lost capsule production but gained anaerobic growth.
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http://dx.doi.org/10.1016/j.tim.2017.05.006DOI Listing
July 2017

Acquisition of the capsule locus by horizontal gene transfer in Neisseria meningitidis is often accompanied by the loss of UDP-GalNAc synthesis.

Sci Rep 2017 03 14;7:44442. Epub 2017 Mar 14.

School of Biomedical Sciences, University of Western Australia, Perth, Australia.

Pathogenic meningococci have acquired a 24 kb capsule synthesis island (cps) by horizontal gene transfer which consists of a synthetic locus and associated capsule transport genes flanked by repetitive Regions D and D'. Regions D and D' contain an intact gene encoding a UDP-galactose epimerase (galE1) and a truncated remnant (galE2), respectively. In this study, GalE protein alleles were shown to be either mono-functional, synthesising UDP-galactose (UDP-Gal), or bi-functional, synthesising UDP-Gal and UDP-galactosamine (UDP-GalNAc). Meningococci possessing a capsule null locus (cnl) typically possessed a single bi-functional galE. Separation of functionality between galE1 and galE2 alleles in meningococcal isolates was retained for all serogroups except serogroup E which has a synthetic requirement for UDP-GalNAc. The truncated galE2 remnant in Region D' was also phylogenetically related to the bi-functional galE of the cnl locus suggesting common ancestry. A model is proposed in which the illegitimate recombination of the cps island into the galE allele of the cnl locus results in the formation of Region D' containing the truncated galE2 locus and the capture of the cps island en bloc. The retention of the duplicated Regions D and D' enables inversion of the synthetic locus within the cps island during bacterial growth.
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http://dx.doi.org/10.1038/srep44442DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5349592PMC
March 2017

Structure of a lipid A phosphoethanolamine transferase suggests how conformational changes govern substrate binding.

Proc Natl Acad Sci U S A 2017 02 13;114(9):2218-2223. Epub 2017 Feb 13.

School of Molecular Sciences, University of Western Australia, Crawley, WA 6009, Australia;

Multidrug-resistant (MDR) gram-negative bacteria have increased the prevalence of fatal sepsis in modern times. Colistin is a cationic antimicrobial peptide (CAMP) antibiotic that permeabilizes the bacterial outer membrane (OM) and has been used to treat these infections. The OM outer leaflet is comprised of endotoxin containing lipid A, which can be modified to increase resistance to CAMPs and prevent clearance by the innate immune response. One type of lipid A modification involves the addition of phosphoethanolamine to the 1 and 4' headgroup positions by phosphoethanolamine transferases. Previous structural work on a truncated form of this enzyme suggested that the full-length protein was required for correct lipid substrate binding and catalysis. We now report the crystal structure of a full-length lipid A phosphoethanolamine transferase from , determined to 2.75-Å resolution. The structure reveals a previously uncharacterized helical membrane domain and a periplasmic facing soluble domain. The domains are linked by a helix that runs along the membrane surface interacting with the phospholipid head groups. Two helices located in a periplasmic loop between two transmembrane helices contain conserved charged residues and are implicated in substrate binding. Intrinsic fluorescence, limited proteolysis, and molecular dynamics studies suggest the protein may sample different conformational states to enable the binding of two very different- sized lipid substrates. These results provide insights into the mechanism of endotoxin modification and will aid a structure-guided rational drug design approach to treating multidrug-resistant bacterial infections.
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http://dx.doi.org/10.1073/pnas.1612927114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5338521PMC
February 2017

Inhibitors of macrophage infectivity potentiator-like PPIases affect neisserial and chlamydial pathogenicity.

Int J Antimicrob Agents 2016 Oct 1;48(4):401-8. Epub 2016 Aug 1.

Biocenter, Chair of Microbiology, University of Würzburg, Am Hubland, 97074 Würzburg, Germany. Electronic address:

The pathogenic bacteria Chlamydia trachomatis, Neisseria gonorrhoeae and Neisseria meningitidis express the surface-exposed macrophage infectivity potentiator (MIP)-like protein, which plays a role in their pathogenicity. MIP exhibits a peptidyl-prolyl isomerase (PPIase) activity that is inhibited by rapamycin and FK506. In this study, pipecolic acid derivatives were tested for their activity against the chlamydial and neisserial MIP. Two MIP inhibitors were identified, PipN3 and PipN4, that affected the developmental cycle of C. trachomatis in HeLa cells. Furthermore, we could show that deletion of neisserial MIP or addition of the two MIP inhibitors affected the survival of N. gonorrhoeae in the presence of neutrophils. Furthermore, both compounds inhibited the adherence, invasion and/or survival of N. meningitidis in epithelial cells. These results confirm the importance of MIP-like proteins in infection and indicate the relevance of pipecolic acid derivatives as antimicrobials against C. trachomatis, N. gonorrhoeae and N. meningitidis.
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http://dx.doi.org/10.1016/j.ijantimicag.2016.06.020DOI Listing
October 2016

Temporal Changes in BEXSERO® Antigen Sequence Type Associated with Genetic Lineages of Neisseria meningitidis over a 15-Year Period in Western Australia.

PLoS One 2016 29;11(6):e0158315. Epub 2016 Jun 29.

Marshall Centre for Infectious Disease Research and Training, School of Pathology and Laboratory Medicine, University of Western Australia, Perth, Australia.

Neisseria meningitidis is the causative agent of invasive meningococcal disease (IMD). The BEXSERO® vaccine which is used to prevent serogroup B disease is composed of four sub-capsular protein antigens supplemented with an outer membrane vesicle. Since the sub-capsular protein antigens are variably expressed and antigenically variable amongst meningococcal isolates, vaccine coverage can be estimated by the meningococcal antigen typing system (MATS) which measures the propensity of the strain to be killed by vaccinated sera. Whole genome sequencing (WGS) which identifies the alleles of the antigens that may be recognised by the antibody response could represent, in future, an alternative estimate of coverage. In this study, WGS of 278 meningococcal isolates responsible for 62% of IMD in Western Australia from 2000-2014 were analysed for association of genetic lineage (sequence type [ST], clonal complex [cc]) with BEXSERO® antigen sequence type (BAST) and MATS to predict the annual vaccine coverage. A hyper-endemic period of IMD between 2000-05 was caused by cc41/44 with the major sequence type of ST-146 which was not predicted by MATS or BAST to be covered by the vaccine. An increase in serogroup diversity was observed between 2010-14 with the emergence of cc11 serogroup W in the adolescent population and cc23 serogroup Y in the elderly. BASTs were statistically associated with clonal complex although individual antigens underwent antigenic drift from the major type. BAST and MATS predicted an annual range of 44-91% vaccine coverage. Periods of low vaccine coverage in years post-2005 were not a result of the resurgence of cc41/44:ST-146 but were characterised by increased diversity of clonal complexes expressing BASTs which were not predicted by MATS to be covered by the vaccine. The driving force behind the diversity of the clonal complex and BAST during these periods of low vaccine coverage is unknown, but could be due to immune selection and inter-strain competition with carriage of non-disease causing meningococci.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0158315PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4927168PMC
July 2017

Novel Moraxella catarrhalis prophages display hyperconserved non-structural genes despite their genomic diversity.

BMC Genomics 2015 Oct 24;16:860. Epub 2015 Oct 24.

School of Pathology and Laboratory Medicine, The University of Western Australia, Perth, WA, Australia.

Background: Moraxella catarrhalis is an important pathogen that often causes otitis media in children, a disease that is not currently vaccine preventable. Asymptomatic colonisation of the human upper respiratory tract is common and lack of clearance by the immune system is likely due to the emergence of seroresistant genetic lineages. No active bacteriophages or prophages have been described in this species. This study was undertaken to identify and categorise prophages in M. catarrhalis, their genetic diversity and the relationship of such diversity with the host-species phylogeny.

Results: This study presents a comparative analysis of 32 putative prophages identified in 95 phylogenetically variable, newly sequenced M. catarrhalis genomes. The prophages were genotypically classified into four diverse clades. The genetic synteny of each clade is similar to the group 1 phage family Siphoviridae, however, they form genotypic clusters that are distinct from other members of this family. No core genetic sequences exist across the 32 prophages despite clades 2, 3, and 4 sharing the most sequence identity. The analysis of non-structural prophage genes (coding the integrase, and terminase), and portal gene showed that the respective genes were identical for clades 2, 3, and 4, but unique for clade 1. Empirical analysis calculated that these genes are unexpectedly hyperconserved, under purifying selection, suggesting a tightly regulated functional role. As such, it is improbable that the prophages are decaying remnants but stable components of a fluctuating, flexible and unpredictable system ultimately maintained by functional constraints on non-structural and packaging genes. Additionally, the plate encoding genes were well conserved across all four prophage clades, and the tail fibre genes, commonly responsible for receptor recognition, were clustered into three major groups distributed across the prophage clades. A pan-genome of 283,622 bp was identified, and the prophages were mapped onto the diverse M. catarrhalis multi-locus sequence type (MLST) backbone.

Conclusion: This study has provided the first evidence of putatively mobile prophages in M. catarrhalis, identifying a diverse and fluctuating system dependent on the hyperconservation of a few key, non-structural genes. Some prophages harbour virulence-related genes, and potentially influence the physiology and virulence of M. catarrhalis. Importantly our data will provide supporting information on the identification of novel prophages in other species by adding greater weight to the identification of non-structural genes.
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http://dx.doi.org/10.1186/s12864-015-2104-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4619438PMC
October 2015

Influence of in situ progressive N-terminal is still controversial truncation of glycogen branching enzyme in Escherichia coli DH5α on glycogen structure, accumulation, and bacterial viability.

BMC Microbiol 2015 May 7;15:96. Epub 2015 May 7.

School of Chemistry and Biochemistry, University of Western Australia, Perth, Australia.

Background: Glycogen average chain length (ACL) has been linked with bacterial durability, but this was on the basis of observations across different species. We therefore wished to investigate the relationship between bacterial durability and glycogen ACL by varying glycogen average chain length in a single species. It has been shown that progressive shortening of the N-terminus of glycogen branching enzyme (GBE) leads to a lengthening of oligosaccharide inter-α-1,6-glycosidic chain lengths, so we sought to harness this to create a set of Escherichia coli DH5α strains with a range of glycogen average chain lengths, and assess these strains for durability related attributes, such as starvation, cold and desiccation stress resistance, and biofilm formation.

Results: A series of Escherichia coli DH5α mutants were created with glgB genes that were in situ progressively N-terminus truncated. N-terminal truncation shifted the distribution of glycogen chain lengths from 5-11 DP toward 13-50 DP, but the relationship between glgB length and glycogen ACL was not linear. Surprisingly, removal of the first 270 nucleotides of glgB (glgBΔ270) resulted in comparatively high glycogen accumulation, with the glycogen having short ACL. Complete knockout of glgB led to the formation of amylose-like glycogen containing long, linear α1,4-glucan chains with significantly reduced branching frequency. Physiologically, the set of mutant strains had reduced bacterial starvation resistance, while minimally increasing bacterial desiccation resistance. Finally, although there were no obvious changes in cold stress resistance or biofilm forming ability, one strain (glgBΔ180) had significantly increased biofilm formation in favourable media.

Conclusions: Despite glgB being the first gene of an operon, it is clear that in situ mutation is a viable means to create more biologically relevant mutant strains. Secondly, there was the suggestion in the data that impairments of starvation, cold and desiccation resistance were worse for the strain lacking glgB, though the first of these was not statistically significant. The results provide prima facie evidence linking abiotic stress tolerance with shorter glycogen ACL. However, further work needs to be done, perhaps in a less labile species. Further work is also required to tease out the complex relationship between glycogen abundance and glycogen structure.
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http://dx.doi.org/10.1186/s12866-015-0421-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4433092PMC
May 2015

The role of oxidoreductases in determining the function of the neisserial lipid A phosphoethanolamine transferase required for resistance to polymyxin.

PLoS One 2014 12;9(9):e106513. Epub 2014 Sep 12.

School of Pathology and Laboratory Medicine, and The Marshall Center for Infectious Diseases, Research and Training, University of Western Australia, Perth, Western Australia, Australia.

The decoration of the lipid A headgroups of the lipooligosaccharide (LOS) by the LOS phosphoethanolamine (PEA) transferase (LptA) in Neisseria spp. is central for resistance to polymyxin. The structure of the globular domain of LptA shows that the protein has five disulphide bonds, indicating that it is a potential substrate of the protein oxidation pathway in the bacterial periplasm. When neisserial LptA was expressed in Escherichia coli in the presence of the oxidoreductase, EcDsbA, polymyxin resistance increased 30-fold. LptA decorated one position of the E. coli lipid A headgroups with PEA. In the absence of the EcDsbA, LptA was degraded in E. coli. Neisseria spp. express three oxidoreductases, DsbA1, DsbA2 and DsbA3, each of which appear to donate disulphide bonds to different targets. Inactivation of each oxidoreductase in N. meningitidis enhanced sensitivity to polymyxin with combinatorial mutants displaying an additive increase in sensitivity to polymyxin, indicating that the oxidoreductases were required for multiple pathways leading to polymyxin resistance. Correlates were sought between polymyxin sensitivity, LptA stability or activity and the presence of each of the neisserial oxidoreductases. Only meningococcal mutants lacking DsbA3 had a measurable decrease in the amount of PEA decoration on lipid A headgroups implying that LptA stability was supported by the presence of DsbA3 but did not require DsbA1/2 even though these oxidoreductases could oxidise the protein. This is the first indication that DsbA3 acts as an oxidoreductase in vivo and that multiple oxidoreductases may be involved in oxidising the one target in N. meningitidis. In conclusion, LptA is stabilised by disulphide bonds within the protein. This effect was more pronounced when neisserial LptA was expressed in E. coli than in N. meningitidis and may reflect that other factors in the neisserial periplasm have a role in LptA stability.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0106513PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4162559PMC
May 2015

The use of high-throughput DNA sequencing in the investigation of antigenic variation: application to Neisseria species.

PLoS One 2014 22;9(1):e86704. Epub 2014 Jan 22.

Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois, United States of America.

Antigenic variation occurs in a broad range of species. This process resembles gene conversion in that variant DNA is unidirectionally transferred from partial gene copies (or silent loci) into an expression locus. Previous studies of antigenic variation have involved the amplification and sequencing of individual genes from hundreds of colonies. Using the pilE gene from Neisseria gonorrhoeae we have demonstrated that it is possible to use PCR amplification, followed by high-throughput DNA sequencing and a novel assembly process, to detect individual antigenic variation events. The ability to detect these events was much greater than has previously been possible. In N. gonorrhoeae most silent loci contain multiple partial gene copies. Here we show that there is a bias towards using the copy at the 3' end of the silent loci (copy 1) as the donor sequence. The pilE gene of N. gonorrhoeae and some strains of Neisseria meningitidis encode class I pilin, but strains of N. meningitidis from clonal complexes 8 and 11 encode a class II pilin. We have confirmed that the class II pili of meningococcal strain FAM18 (clonal complex 11) are non-variable, and this is also true for the class II pili of strain NMB from clonal complex 8. In addition when a gene encoding class I pilin was moved into the meningococcal strain NMB background there was no evidence of antigenic variation. Finally we investigated several members of the opa gene family of N. gonorrhoeae, where it has been suggested that limited variation occurs. Variation was detected in the opaK gene that is located close to pilE, but not at the opaJ gene located elsewhere on the genome. The approach described here promises to dramatically improve studies of the extent and nature of antigenic variation systems in a variety of species.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0086704PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3899283PMC
November 2014

The structure of the neisserial lipooligosaccharide phosphoethanolamine transferase A (LptA) required for resistance to polymyxin.

J Mol Biol 2013 Sep 28;425(18):3389-402. Epub 2013 Jun 28.

School of Chemistry and Biochemistry, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.

Gram-negative bacteria possess an outer membrane envelope consisting of an outer leaflet of lipopolysaccharides, also called endotoxins, which protect the pathogen from antimicrobial peptides and have multifaceted roles in virulence. Lipopolysaccharide consists of a glycan moiety attached to lipid A, embedded in the outer membrane. Modification of the lipid A headgroups by phosphoethanolamine (PEA) or 4-amino-arabinose residues increases resistance to the cationic cyclic polypeptide antibiotic, polymyxin. Lipid A PEA transferases are members of the YhjW/YjdB/YijP superfamily and usually consist of a transmembrane domain anchoring the enzyme to the periplasmic face of the cytoplasmic membrane attached to a soluble catalytic domain. The crystal structure of the soluble domain of the protein of the lipid A PEA transferase from Neisseria meningitidis has been determined crystallographically and refined to 1.4Å resolution. The structure reveals a core hydrolase fold similar to that of alkaline phosphatase. Loop regions in the structure differ, presumably to enable interaction with the membrane-localized substrates and to provide substrate specificity. A phosphorylated form of the putative nucleophile, Thr280, is observed. Metal ions present in the active site are coordinated to Thr280 and to residues conserved among the family of transferases. The structure reveals the protein components needed for the transferase chemistry; however, substrate-binding regions are not evident and are likely to reside in the transmembrane domain of the protein.
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http://dx.doi.org/10.1016/j.jmb.2013.06.029DOI Listing
September 2013

Attachment and invasion of Neisseria meningitidis to host cells is related to surface hydrophobicity, bacterial cell size and capsule.

PLoS One 2013 6;8(2):e55798. Epub 2013 Feb 6.

School of Pathology and Laboratory Medicine, The University of Western Australia, Perth, Western Australia, Australia.

We compared exemplar strains from two hypervirulent clonal complexes, strain NMB-CDC from ST-8/11 cc and strain MC58 from ST-32/269 cc, in host cell attachment and invasion. Strain NMB-CDC attached to and invaded host cells at a significantly greater frequency than strain MC58. Type IV pili retained the primary role for initial attachment to host cells for both isolates regardless of pilin class and glycosylation pattern. In strain MC58, the serogroup B capsule was the major inhibitory determinant affecting both bacterial attachment to and invasion of host cells. Removal of terminal sialylation of lipooligosaccharide (LOS) in the presence of capsule did not influence rates of attachment or invasion for strain MC58. However, removal of either serogroup B capsule or LOS sialylation in strain NMB-CDC increased bacterial attachment to host cells to the same extent. Although the level of inhibition of attachment by capsule was different between these strains, the regulation of the capsule synthesis locus by the two-component response regulator MisR, and the level of surface capsule determined by flow cytometry were not significantly different. However, the diplococci of strain NMB-CDC were shown to have a 1.89-fold greater surface area than strain MC58 by flow cytometry. It was proposed that the increase in surface area without changing the amount of anchored glycolipid capsule in the outer membrane would result in a sparser capsule and increase surface hydrophobicity. Strain NMB-CDC was shown to be more hydrophobic than strain MC58 using hydrophobicity interaction chromatography and microbial adhesion-to-solvents assays. In conclusion, improved levels of adherence of strain NMB-CDC to cell lines was associated with increased bacterial cell surface and surface hydrophobicity. This study shows that there is diversity in bacterial cell surface area and surface hydrophobicity within N. meningitidis which influence steps in meningococcal pathogenesis.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0055798PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3566031PMC
August 2013

A comparison of the endotoxin biosynthesis and protein oxidation pathways in the biogenesis of the outer membrane of Escherichia coli and Neisseria meningitidis.

Front Cell Infect Microbiol 2012 20;2:162. Epub 2012 Dec 20.

Department of Pathology and Laboratory Medicine, The University of Western Australia Perth, WA, Australia.

The Gram-negative bacterial cell envelope consists of an inner membrane (IM) that surrounds the cytoplasm and an asymmetrical outer-membrane (OM) that forms a protective barrier to the external environment. The OM consists of lipopolysaccahride (LPS), phospholipids, outer membrane proteins (OMPs), and lipoproteins. Oxidative protein folding mediated by periplasmic oxidoreductases is required for the biogenesis of the protein components, mainly constituents of virulence determinants such as pili, flagella, and toxins, of the Gram-negative OM. Recently, periplasmic oxidoreductases have been implicated in LPS biogenesis of Escherichia coli and Neisseria meningitidis. Differences in OM biogenesis, in particular the transport pathways for endotoxin to the OM, the composition and role of the protein oxidation, and isomerization pathways and the regulatory networks that control them have been found in these two Gram-negative species suggesting that although form and function of the OM is conserved, the pathways required for the biosynthesis of the OM and the regulatory circuits that control them have evolved to suit the lifestyle of each organism.
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http://dx.doi.org/10.3389/fcimb.2012.00162DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3526765PMC
December 2013