Publications by authors named "Patrik M Bavoil"

40 Publications

The association of Chlamydia trachomatis and Mycoplasma genitalium infection with the vaginal metabolome.

Sci Rep 2020 02 25;10(1):3420. Epub 2020 Feb 25.

Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA.

Chlamydia trachomatis (CT) and Mycoplasma genitalium (MG) are two highly prevalent bacterial sexually transmitted infections (STIs) with a significant rate of co-infection in some populations. Vaginal metabolites are influenced by resident vaginal microbiota, affect susceptibility to sexually transmitted infections (STIs), and may impact local inflammation and patient symptoms. Examining the vaginal metabolome in the context of CT mono (CT+) and CT/MG co-infection (CT+/MG+) may identify biomarkers for infection or provide new insights into disease etiology and pathogenesis. Yet, the vaginal metabolome in the setting of CT infection is understudied and the composition of the vaginal metabolome in CT/MG co-infected women is unknown. Therefore, in this analysis, we used an untargeted metabolomic approach combined with 16S rRNA gene amplicon sequencing to characterize the vaginal microbiota and metabolomes of CT+, CT+/MG+, and uninfected women. We found that CT+ and CT+/MG+ women had distinct vaginal metabolomic profiles as compared to uninfected women both before and after adjustment for the vaginal microbiota. This study provides important foundational data documenting differences in the vaginal metabolome between CT+, CT+/MG+ and uninfected women. These data may guide future mechanistic studies that seek to provide insight into the pathogenesis of CT and CT/MG infections.
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http://dx.doi.org/10.1038/s41598-020-60179-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7042340PMC
February 2020

Insertional mutagenesis in the zoonotic pathogen Chlamydia caviae.

PLoS One 2019 7;14(11):e0224324. Epub 2019 Nov 7.

Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research, Department of Molecular Biology, Umeå University, Umeå, Sweden.

The ability to introduce targeted genetic modifications in microbial genomes has revolutionized our ability to study the role and mode of action of individual bacterial virulence factors. Although the fastidious lifestyle of obligate intracellular bacterial pathogens poses a technical challenge to such manipulations, the last decade has produced significant advances in our ability to conduct molecular genetic analysis in Chlamydia trachomatis, a major bacterial agent of infertility and blindness. Similar approaches have not been established for the closely related veterinary Chlamydia spp., which cause significant economic damage, as well as rare but potentially life-threatening infections in humans. Here we demonstrate the feasibility of conducting site-specific mutagenesis for disrupting virulence genes in C. caviae, an agent of guinea pig inclusion conjunctivitis that was recently identified as a zoonotic agent in cases of severe community-acquired pneumonia. Using this approach, we generated C. caviae mutants deficient for the secreted effector proteins IncA and SinC. We demonstrate that C. caviae IncA plays a role in mediating fusion of the bacteria-containing vacuoles inhabited by C. caviae. Moreover, using a chicken embryo infection model, we provide first evidence for a role of SinC in C. caviae virulence in vivo.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0224324PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6837515PMC
March 2020

Nonoptimal Vaginal Microbiota After Azithromycin Treatment for Chlamydia trachomatis Infection.

J Infect Dis 2020 02;221(4):627-635

Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, Maryland, USA.

We characterized the composition and structure of the vaginal microbiota in a cohort of 149 women with genital Chlamydia trachomatis infection at baseline who were followed quarterly for 9 months after antibiotic treatment. At time of diagnosis, the vaginal microbiota was dominated by Lactobacillus iners or a diverse array of bacterial vaginosis-associated bacteria including Gardnerella vaginalis. Interestingly, L. iners-dominated communities were most common after azithromycin treatment (1 g monodose), consistent with the observed relative resistance of L. iners to azithromycin. Lactobacillus iners-dominated communities have been associated with increased risk of C. trachomatis infection, suggesting that the impact of antibiotic treatment on the vaginal microbiota could favor reinfections. These results provide support for the dual need to account for the potential perturbing effect(s) of antibiotic treatment on the vaginal microbiota, and to develop strategies to protect and restore optimal vaginal microbiota.
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http://dx.doi.org/10.1093/infdis/jiz499DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7530545PMC
February 2020

The Cervicovaginal Microbiota-Host Interaction Modulates Chlamydia trachomatis Infection.

mBio 2019 08 13;10(4). Epub 2019 Aug 13.

Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, Maryland, USA

The mechanism(s) by which -dominated cervicovaginal microbiota provide a barrier to infection remain(s) unknown. Here we evaluate the impact of different spp. identified via culture-independent metataxonomic analysis of -infected women on infection in a three-dimensional (3D) cervical epithelium model. spp. that specifically produce d(-) lactic acid were associated with long-term protection against infection, consistent with reduced protection associated with , which does not produce this isoform, and with decreased epithelial cell proliferation, consistent with the observed prolonged protective effect. Transcriptomic analysis revealed that epigenetic modifications involving histone deacetylase-controlled pathways are integral to the cross talk between host and microbiota. These results highlight a fundamental mechanism whereby the cervicovaginal microbiota modulates host functions to protect against infection. The vaginal microbiota is believed to protect women against , the etiologic agent of the most prevalent sexually transmitted infection (STI) in developed countries. The mechanism underlying this protection has remained elusive. Here, we reveal the comprehensive strategy by which the cervicovaginal microbiota modulates host functions to protect against chlamydial infection, thereby providing a novel conceptual mechanistic understanding. Major implications of this work are that (i) the impact of the vaginal microbiota on the epithelium should be considered in future studies of chlamydial infection and other STIs and (ii) a fundamental understanding of the cervicovaginal microbiota's role in protection against STIs may enable the development of novel microbiome-based therapeutic strategies to protect women from infection and improve vaginal and cervical health.
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http://dx.doi.org/10.1128/mBio.01548-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6692509PMC
August 2019

Does Active Oral Sex Contribute to Female Infertility?

J Infect Dis 2017 11;216(8):932-935

Department of Microbiology and Immunology.

Based on recent, historical, and circumstantial evidence, we present a multifactorial hypothesis that has potential direct implications on the epidemiology and management of chlamydial infection and disease in humans. We propose that (1) like its veterinary relatives, the oculogenital pathogen Chlamydia trachomatis evolved as a commensal organism of the human gastrointestinal (GI) tract primarily transmissible via the fecal-oral route; (2) in the modern era, C. trachomatis causes "opportunistic" infection at non-GI sites under conditions driven by improved sanitation/hygiene and reduced fecal-oral transmission; and (3) the rise in the practice of oral sex is contributing to the increased prevalence of C. trachomatis in the human GI tract. Infectious organisms produced in the GI tract and reaching the rectum may then chronically contaminate and infect the female urogenital tract, thereby potentially contributing to the most serious sequelae of chlamydial infection in women: pelvic inflammatory disease, ectopic pregnancy, and tubal factor infertility.
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http://dx.doi.org/10.1093/infdis/jix419DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5789812PMC
November 2017

Engineering of obligate intracellular bacteria: progress, challenges and paradigms.

Nat Rev Microbiol 2017 Sep 19;15(9):544-558. Epub 2017 Jun 19.

Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.

It is estimated that approximately one billion people are at risk of infection with obligate intracellular bacteria, but little is known about the underlying mechanisms that govern their life cycles. The difficulty in studying Chlamydia spp., Coxiella spp., Rickettsia spp., Anaplasma spp., Ehrlichia spp. and Orientia spp. is, in part, due to their genetic intractability. Recently, genetic tools have been developed; however, optimizing the genomic manipulation of obligate intracellular bacteria remains challenging. In this Review, we describe the progress in, as well as the constraints that hinder, the systematic development of a genetic toolbox for obligate intracellular bacteria. We highlight how the use of genetically manipulated pathogens has facilitated a better understanding of microbial pathogenesis and immunity, and how the engineering of obligate intracellular bacteria could enable the discovery of novel signalling circuits in host-pathogen interactions.
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http://dx.doi.org/10.1038/nrmicro.2017.59DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5557331PMC
September 2017

Whole-Genome Sequence of Chlamydia gallinacea Type Strain 08-1274/3.

Genome Announc 2016 Jul 21;4(4). Epub 2016 Jul 21.

RNA Bioinformatics and High-Throughput Analysis, Faculty of Mathematics and Computer Science, Friedrich-Schiller-Universität, Jena, Germany Institute of Molecular Pathogenesis, Friedrich-Loeffler-Institut (Federal Research Institute for Animal Health), Jena, Germany

The recently introduced bacterial species Chlamydia gallinacea is known to occur in domestic poultry and other birds. Its potential as an avian pathogen and zoonotic agent is under investigation. The whole-genome sequence of its type strain, 08-1274/3, consists of a 1,059,583-bp chromosome with 914 protein-coding sequences (CDSs) and a plasmid (p1274) comprising 7,619 bp with 9 CDSs.
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http://dx.doi.org/10.1128/genomeA.00708-16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4956461PMC
July 2016

SINC, a type III secreted protein of Chlamydia psittaci, targets the inner nuclear membrane of infected cells and uninfected neighbors.

Mol Biol Cell 2015 May 18;26(10):1918-34. Epub 2015 Mar 18.

Department of Microbial Pathogenesis, University of Maryland School of Dentistry, Baltimore, MD 21201

SINC, a new type III secreted protein of the avian and human pathogen Chlamydia psittaci, uniquely targets the nuclear envelope of C. psittaci-infected cells and uninfected neighboring cells. Digitonin-permeabilization studies of SINC-GFP-transfected HeLa cells indicate that SINC targets the inner nuclear membrane. SINC localization at the nuclear envelope was blocked by importazole, confirming SINC import into the nucleus. Candidate partners were identified by proximity to biotin ligase-fused SINC in HEK293 cells and mass spectrometry (BioID). This strategy identified 22 candidates with high confidence, including the nucleoporin ELYS, lamin B1, and four proteins (emerin, MAN1, LAP1, and LBR) of the inner nuclear membrane, suggesting that SINC interacts with host proteins that control nuclear structure, signaling, chromatin organization, and gene silencing. GFP-SINC association with the native LEM-domain protein emerin, a conserved component of nuclear "lamina" structure, or with a complex containing emerin was confirmed by GFP pull down. Our findings identify SINC as a novel bacterial protein that targets the nuclear envelope with the capability of globally altering nuclear envelope functions in the infected host cell and neighboring uninfected cells. These properties may contribute to the aggressive virulence of C. psittaci.
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http://dx.doi.org/10.1091/mbc.E14-11-1530DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4436835PMC
May 2015

Chlamydia caviae infection alters abundance but not composition of the guinea pig vaginal microbiota.

Pathog Dis 2015 Jun 10;73(4). Epub 2015 Mar 10.

Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD 21201, USA Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD 21201, USA

In humans, the vaginal microbiota is thought to be the first line of defense again pathogens including Chlamydia trachomatis. The guinea pig has been extensively used as a model to study chlamydial infection because it shares anatomical and physiological similarities with humans, such as a squamous vaginal epithelium as well as some of the long-term outcomes caused by chlamydial infection. In this study, we aimed to evaluate the guinea pig-C. caviae model of genital infection as a surrogate for studying the role of the vaginal microbiota in the early steps of C. trachomatis infection in humans. We used culture-independent molecular methods to characterize the relative and absolute abundance of bacterial phylotypes in the guinea pig vaginal microbiota in animals non-infected, mock-infected or infected by C. caviae. We showed that the guinea pig and human vaginal microbiotas are of different bacterial composition and abundance. Chlamydia caviae infection had a profound effect on the absolute abundance of bacterial phylotypes but not on the composition of the guinea pig vaginal microbiota. Our findings compromise the validity of the guinea pig-C. caviae model to study the role of the vaginal microbiota during the early steps of sexually transmitted infection.
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http://dx.doi.org/10.1093/femspd/ftv019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4445005PMC
June 2015

Emendation of the family Chlamydiaceae: proposal of a single genus, Chlamydia, to include all currently recognized species.

Syst Appl Microbiol 2015 Mar 8;38(2):99-103. Epub 2015 Jan 8.

Department of Microbiology and Ecosystem Science, University of Vienna, Vienna, Austria.

The family Chlamydiaceae (order Chlamydiales, phylum Chlamydiae) comprises important, obligate intracellular bacterial pathogens of humans and animals. Subdivision of the family into the two genera Chlamydia and Chlamydophila has been discussed controversially during the past decade. Here, we have revisited the current classification in the light of recent genomic data and in the context of the unique biological properties of these microorganisms. We conclude that neither generally used 16S rRNA sequence identity cut-off values nor parameters based on genomic similarity consistently separate the two genera. Notably, no easily recognizable phenotype such as host preference or tissue tropism is available that would support a subdivision. In addition, the genus Chlamydophila is currently not well accepted and not used by a majority of research groups in the field. Therefore, we propose the classification of all 11 currently recognized Chlamydiaceae species in a single genus, the genus Chlamydia. Finally, we provide emended descriptions of the family Chlamydiaceae, the genus Chlamydia, as well as the species Chlamydia abortus, Chlamydia caviae and Chlamydia felis.
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http://dx.doi.org/10.1016/j.syapm.2014.12.004DOI Listing
March 2015

Analysis of CPAF mutants: new functions, new questions (the ins and outs of a chlamydial protease).

Pathog Dis 2014 Aug;71(3):287-91

Department of Microbial Pathogenesis, University of Maryland School of Dentistry, Baltimore, MD, USA.

The role of the chlamydial protease CPAF, previously described as a secreted serine protease processing a wealth of host and chlamydial proteins to promote chlamydial intracellular growth, has recently been questioned by studies from the groups of Tan and Sütterlin, who demonstrated that the reported proteolysis of almost a dozen substrates by CPAF occurred during preparation of cell lysates rather than in intact cells. Valdivia et al. have now compared near-isogenic pairs of CPAF-deficient and secretion-deficient mutants of Chlamydia trachomatis and their wild-type parent. Their report, published in this issue of Pathogens and Disease, is a landmark study in the emerging era of Chlamydia genetics. The results of Tan and Sütterlin are confirmed with a few additions. While CPAF's role in pathogenesis is diminished considerably from these studies, CPAF remains an important factor in chlamydial biology as (1) CPAF mutants produce less infectious yield than wild type; and (2) CPAF is responsible for proteolytic cleavage of vimentin and LAP-1, but only after lysis of the inclusion membrane, not upon CPAF secretion to the cytosol. Here, we briefly review the evidence in support of CPAF's active secretion from the mid-to-late inclusion and conclude that new experimentation to establish whether or not CPAF is actively secreted should precede any new investigation of CPAF's cellular activities during mid-to-late development.
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http://dx.doi.org/10.1111/2049-632X.12194DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5914542PMC
August 2014

Most influential FEMS publications.

FEMS Microbiol Lett 2014 May;354(2):83-4

Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, UK.

A selection of influential FEMS publications to celebrate the 40th anniversary of FEMS.
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http://dx.doi.org/10.1111/1574-6968.12444DOI Listing
May 2014

What's in a word: the use, misuse, and abuse of the word "persistence" in Chlamydia biology.

Authors:
Patrik M Bavoil

Front Cell Infect Microbiol 2014 4;4:27. Epub 2014 Mar 4.

Department of Microbial Pathogenesis, School of Dentistry, University of Maryland Baltimore, MD, USA.

The word persistence was used by Chlamydia researchers almost as soon as Chlamydia research was born to reflect the propensity of chlamydiae to cause inapparent infection in their hosts, from birds to humans. More recently, the term persistence has been used, misused, and sometimes abused amidst in vitro and in vivo studies that aim to mimick the ability of chlamydiae to emerge from the presumed inapparent state into clinically detectable infection and disease. Here, I have attempted to provide a global perspective on the state of research on chlamydial persistence, revisiting old observations that may warrant a new look, critically evaluating more recent observations and their shortcomings, and including recent developments that may help redefine chlamydiae as pathogens-or not-of both animals and humans.
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http://dx.doi.org/10.3389/fcimb.2014.00027DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3940941PMC
September 2014

Evidence for the existence of two new members of the family Chlamydiaceae and proposal of Chlamydia avium sp. nov. and Chlamydia gallinacea sp. nov.

Syst Appl Microbiol 2014 Mar 22;37(2):79-88. Epub 2014 Jan 22.

Faculty of Mathematics and Computer Science, Friedrich-Schiller-Universität, Jena, Germany.

The family Chlamydiaceae with the recombined single genus Chlamydia currently comprises nine species, all of which are obligate intracellular organisms distinguished by a unique biphasic developmental cycle. Anecdotal evidence from epidemiological surveys in flocks of poultry, pigeons and psittacine birds have indicated the presence of non-classified chlamydial strains, some of which may act as pathogens. In the present study, phylogenetic analysis of ribosomal RNA and ompA genes, as well as multi-locus sequence analysis of 11 field isolates were conducted. All independent analyses assigned the strains into two different clades of monophyletic origin corresponding to pigeon and psittacine strains or poultry isolates, respectively. Comparative genome analysis involving the type strains of currently accepted Chlamydiaceae species and the designated type strains representing the two new clades confirmed that the latter could be classified into two different species as their average nucleotide identity (ANI) values were always below 94%, both with the closest relative species and between themselves. In view of the evidence obtained from the analyses, we propose the addition of two new species to the current classification: Chlamydia avium sp. nov. comprising strains from pigeons and psittacine birds (type strain 10DC88(T); DSMZ: DSM27005(T), CSUR: P3508(T)) and Chlamydia gallinacea sp. nov. comprising strains from poultry (type strain 08-1274/3(T); DSMZ: DSM27451(T), CSUR: P3509(T)).
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http://dx.doi.org/10.1016/j.syapm.2013.12.004DOI Listing
March 2014

Simultaneous transcriptional profiling of bacteria and their host cells.

PLoS One 2013 4;8(12):e80597. Epub 2013 Dec 4.

Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, Maryland, United States of America.

We developed an RNA-Seq-based method to simultaneously capture prokaryotic and eukaryotic expression profiles of cells infected with intracellular bacteria. As proof of principle, this method was applied to Chlamydia trachomatis-infected epithelial cell monolayers in vitro, successfully obtaining transcriptomes of both C. trachomatis and the host cells at 1 and 24 hours post-infection. Chlamydiae are obligate intracellular bacterial pathogens that cause a range of mammalian diseases. In humans chlamydiae are responsible for the most common sexually transmitted bacterial infections and trachoma (infectious blindness). Disease arises by adverse host inflammatory reactions that induce tissue damage & scarring. However, little is known about the mechanisms underlying these outcomes. Chlamydia are genetically intractable as replication outside of the host cell is not yet possible and there are no practical tools for routine genetic manipulation, making genome-scale approaches critical. The early timeframe of infection is poorly understood and the host transcriptional response to chlamydial infection is not well defined. Our simultaneous RNA-Seq method was applied to a simplified in vitro model of chlamydial infection. We discovered a possible chlamydial strategy for early iron acquisition, putative immune dampening effects of chlamydial infection on the host cell, and present a hypothesis for Chlamydia-induced fibrotic scarring through runaway positive feedback loops. In general, simultaneous RNA-Seq helps to reveal the complex interplay between invading bacterial pathogens and their host mammalian cells and is immediately applicable to any bacteria/host cell interaction.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0080597PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3851178PMC
September 2014

Microbiome, sex hormones, and immune responses in the reproductive tract: challenges for vaccine development against sexually transmitted infections.

Vaccine 2014 Mar 14;32(14):1543-52. Epub 2013 Oct 14.

Division of Infectious Diseases, Johns Hopkins University School of Medicine, Baltimore, MD, USA. Electronic address:

The female and male reproductive tracts are complex eco-systems where immune cells, hormones, and microorganisms interact. The characteristics of the reproductive tract mucosa are distinct from other mucosal sites. Reproductive tract mucosal immune responses are compartmentalized, unique, and affected by resident bacterial communities and sex hormones. The female and male genital microbiomes are complex environments that fluctuate in response to external and host-associated stimuli. The female vaginal microbiota play an important role in preventing colonization by pathogenic organisms. Sex hormones and their duration of exposure affect the composition and stability of the microbiome as well as systemic and mucosal immune responses. In addition to the characteristics of the pathogen they are targeting, successful vaccines against sexually transmitted pathogens must take into account the differences between the systemic and mucosal immune responses, the compartmentalization of the mucosal immune responses, the unique characteristics of the reproductive tract mucosa, the role of the mucosal bacterial communities, the impact of sex hormones, and the interactions among all of these factors.
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http://dx.doi.org/10.1016/j.vaccine.2013.10.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3964794PMC
March 2014

Genus-optimized strategy for the identification of chlamydial type III secretion substrates.

Pathog Dis 2013 Dec 14;69(3):213-22. Epub 2013 Aug 14.

Department of Microbial Pathogenesis, University of Maryland School of Dentistry, Baltimore, MD, USA.

Among chlamydial virulence factors are the type III secretion (T3S) system and its effectors. T3S effectors target host proteins to benefit the infecting chlamydiae. The assortment of effectors, each with a unique function, varies between species. This variation likely contributes to differences in host specificity and disease severity. A dozen effectors of Chlamydia trachomatis have been identified; however, estimates suggest that more exist. A T3S prediction algorithm, SVM-based Identification and Evaluation of Virulence Effectors (SIEVE), along with a Yersinia surrogate secretion system helped to identify a new T3S substrate, CT082, which rather than functioning as an effector associates with the chlamydial envelope after secretion. SIEVE was modified to improve/expand effector predictions to include all sequenced genomes. Additional adjustments were made to the existing surrogate system whereby the N terminus of putative effectors was fused to a known effector lacking its own N terminus and was tested for secretion. Expansion of effector predictions by cSIEVE and modification of the surrogate system have also assisted in identifying a new T3S substrate from C. psittaci. The expanded predictions along with modifications to improve the surrogate secretion system have enhanced our ability to identify novel species-specific effectors, which upon characterization should provide insight into the unique pathogenic properties of each species.
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http://dx.doi.org/10.1111/2049-632X.12070DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3838470PMC
December 2013

Fierce competition between Toxoplasma and Chlamydia for host cell structures in dually infected cells.

Eukaryot Cell 2013 Feb 14;12(2):265-77. Epub 2012 Dec 14.

Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, USA.

The prokaryote Chlamydia trachomatis and the protozoan Toxoplasma gondii, two obligate intracellular pathogens of humans, have evolved a similar modus operandi to colonize their host cell and salvage nutrients from organelles. In order to gain fundamental knowledge on the pathogenicity of these microorganisms, we have established a cell culture model whereby single fibroblasts are coinfected by C. trachomatis and T. gondii. We previously reported that the two pathogens compete for the same nutrient pools in coinfected cells and that Toxoplasma holds a significant competitive advantage over Chlamydia. Here we have expanded our coinfection studies by examining the respective abilities of Chlamydia and Toxoplasma to co-opt the host cytoskeleton and recruit organelles. We demonstrate that the two pathogen-containing vacuoles migrate independently to the host perinuclear region and rearrange the host microtubular network around each vacuole. However, Toxoplasma outcompetes Chlamydia to the host microtubule-organizing center to the detriment of the bacterium, which then shifts to a stress-induced persistent state. Solely in cells preinfected with Chlamydia, the centrosomes become associated with the chlamydial inclusion, while the Toxoplasma parasitophorous vacuole displays growth defects. Both pathogens fragment the host Golgi apparatus and recruit Golgi elements to retrieve sphingolipids. This study demonstrates that the productive infection by both Chlamydia and Toxoplasma depends on the capability of each pathogen to successfully adhere to a finely tuned developmental program that aims to remodel the host cell for the pathogen's benefit. In particular, this investigation emphasizes the essentiality of host organelle interception by intravacuolar pathogens to facilitate access to nutrients.
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http://dx.doi.org/10.1128/EC.00313-12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3571308PMC
February 2013

A novel co-infection model with Toxoplasma and Chlamydia trachomatis highlights the importance of host cell manipulation for nutrient scavenging.

Cell Microbiol 2013 Apr 27;15(4):619-46. Epub 2012 Nov 27.

Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD, 21205, USA.

Toxoplasma and Chlamydia trachomatis are obligate intracellular pathogens that have evolved analogous strategies to replicate within mammalian cells. Both pathogens are known to extensively remodel the cytoskeleton, and to recruit endocytic and exocytic organelles to their respective vacuoles. However, how important these activities are for infectivity by either pathogen remains elusive. Here, we have developed a novel co-infection system to gain insights into the developmental cycles of Toxoplasma and C. trachomatis by infecting human cells with both pathogens, and examining their respective ability to replicate and scavenge nutrients. We hypothesize that the common strategies used by Toxoplasma and Chlamydia to achieve development results in direct competition of the two pathogens for the same pool of nutrients. We show that a single human cell can harbour Chlamydia and Toxoplasma. In co-infected cells, Toxoplasma is able to divert the content of host organelles, such as cholesterol. Consequently, the infectious cycle of Toxoplasma progresses unimpeded. In contrast, Chlamydia's ability to scavenge selected nutrients is diminished, and the bacterium shifts to a stress-induced persistent growth. Parasite killing engenders an ordered return to normal chlamydial development. We demonstrate that C. trachomatis enters a stress-induced persistence phenotype as a direct result from being barred from its normal nutrient supplies as addition of excess nutrients, e.g. amino acids, leads to substantial recovery of Chlamydia growth and infectivity. Co-infection of C. trachomatis with slow growing strains of Toxoplasma or a mutant impaired in nutrient acquisition does not restrict chlamydial development. Conversely, Toxoplasma growth is halted in cells infected with the highly virulent Chlamydia psittaci. This study illustrates the key role that cellular remodelling plays in the exploitation of host intracellular resources by Toxoplasma and Chlamydia. It further highlights the delicate balance between success and failure of infection by intracellular pathogens in a co-infection system at the cellular level.
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http://dx.doi.org/10.1111/cmi.12060DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3625693PMC
April 2013

The role of Chlamydia trachomatis polymorphic membrane proteins in inflammation and sequelae among women with pelvic inflammatory disease.

Infect Dis Obstet Gynecol 2011 19;2011:989762. Epub 2011 Oct 19.

Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15261, USA.

Chlamydia trachomatis polymorphic membrane proteins (Pmps) may increase genital tract inflammation and play a role in virulence. Antibody levels for PmpA, PmpD, and PmpI, measured in densitometric units, were assessed among a pilot sample of 40 C. trachomatis-infected women with mild-to-moderate clinical PID. Women who expressed antibodies to PmpA were less likely to achieve pregnancy (40.0% versus 85.7%; P = 0.042) and less likely to have a live birth (0.0% versus 80.0%; P = 0.005) compared to women who did not express antibody to PmpA. Women who expressed antibodies to PmpI were more likely to have upper genital tract infection (61.5% versus 20.0%; P = 0.026). However, seropositivity to PmpI and PmpD did not modify the risk of reproductive sequelae or inflammation. Seropositivity to chlamydial PmpA may represent a biomarker of increased risk of sequelae secondary to infection with C. trachomatis.
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http://dx.doi.org/10.1155/2011/989762DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3199047PMC
January 2012

Unity in variety--the pan-genome of the Chlamydiae.

Mol Biol Evol 2011 Dec 20;28(12):3253-70. Epub 2011 Jun 20.

Department of Microbial Ecology, University of Vienna, Vienna, Austria.

Chlamydiae are evolutionarily well-separated bacteria that live exclusively within eukaryotic host cells. They include important human pathogens such as Chlamydia trachomatis as well as symbionts of protozoa. As these bacteria are experimentally challenging and genetically intractable, our knowledge about them is still limited. In this study, we obtained the genome sequences of Simkania negevensis Z, Waddlia chondrophila 2032/99, and Parachlamydia acanthamoebae UV-7. This enabled us to perform the first comprehensive comparative and phylogenomic analysis of representative members of four major families of the Chlamydiae, including the Chlamydiaceae. We identified a surprisingly large core gene set present in all genomes and a high number of diverse accessory genes in those Chlamydiae that do not primarily infect humans or animals, including a chemosensory system in P. acanthamoebae and a type IV secretion system. In S. negevensis, the type IV secretion system is encoded on a large conjugative plasmid (pSn, 132 kb). Phylogenetic analyses suggested that a plasmid similar to the S. negevensis plasmid was originally acquired by the last common ancestor of all four families and that it was subsequently reduced, integrated into the chromosome, or lost during diversification, ultimately giving rise to the extant virulence-associated plasmid of pathogenic chlamydiae. Other virulence factors, including a type III secretion system, are conserved among the Chlamydiae to variable degrees and together with differences in the composition of the cell wall reflect adaptation to different host cells including convergent evolution among the four chlamydial families. Phylogenomic analysis focusing on chlamydial proteins with homology to plant proteins provided evidence for the acquisition of 53 chlamydial genes by a plant progenitor, lending further support for the hypothesis of an early interaction between a chlamydial ancestor and the primary photosynthetic eukaryote.
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http://dx.doi.org/10.1093/molbev/msr161DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3247790PMC
December 2011

Altered developmental expression of polymorphic membrane proteins in penicillin-stressed Chlamydia trachomatis.

Cell Microbiol 2011 Jul 26;13(7):1014-25. Epub 2011 Apr 26.

Department of Microbial Pathogenesis, University of Maryland Dental School, 650 West Baltimore Street, Baltimore, MD 21201, USA.

Late Chlamydia trachomatis inclusions express each member of the surface-exposed polymorphic membrane protein family (Pmp subtypes A through I) with a reproducible distribution of fully-on, fully-off and intermediate phenotypes. This observation is consistent with observed variable Pmp antibody profiles in C. trachomatis-infected patients and has led to the hypothesis that the pmp gene family forms the basis of a phase variation-like mechanism of antigenic variation. Here we investigate and compare the developmental expression of each of the nine pmp genes under conditions of optimal in vitro growth with that under conditions that promote prolonged survival of chlamydiae when exposed to penicillin-induced stress. We demonstrate that the pmp gene family includes distinct transcriptional units that are differentially expressed along development and differentially responsive to stress. In particular, our results indicate that expression of pmpA, pmpD and pmpI is uniquely unaffected by stress, suggesting that the PmpA, PmpD and PmpI proteins play a critical role in the pathogenesis of C. trachomatis.
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http://dx.doi.org/10.1111/j.1462-5822.2011.01598.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3116966PMC
July 2011

Comparison of koala LPCoLN and human strains of Chlamydia pneumoniae highlights extended genetic diversity in the species.

BMC Genomics 2010 Jul 21;11:442. Epub 2010 Jul 21.

Faculty of Science and Technology, Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Grove, Queensland 4059, Australia.

Background: Chlamydia pneumoniae is a widespread pathogen causing upper and lower respiratory tract infections in addition to a range of other diseases in humans and animals. Previous whole genome analyses have focused on four essentially clonal (> 99% identity) C. pneumoniae human genomes (AR39, CWL029, J138 and TW183), providing relatively little insight into strain diversity and evolution of this species.

Results: We performed individual gene-by-gene comparisons of the recently sequenced C. pneumoniae koala genome and four C. pneumoniae human genomes to identify species-specific genes, and more importantly, to gain an insight into the genetic diversity and evolution of the species. We selected genes dispersed throughout the chromosome, representing genes that were specific to C. pneumoniae, genes with a demonstrated role in chlamydial biology and/or pathogenicity (n = 49), genes encoding nucleotide salvage or amino acid biosynthesis proteins (n = 6), and extrachromosomal elements (9 plasmid and 2 bacteriophage genes).

Conclusions: We have identified strain-specific differences and targets for detection of C. pneumoniae isolates from both human and animal origin. Such characterisation is necessary for an improved understanding of disease transmission and intervention.
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http://dx.doi.org/10.1186/1471-2164-11-442DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3091639PMC
July 2010

Differential identification of Chlamydophila abortus live vaccine strain 1B and C. abortus field isolates by PCR-RFLP.

Vaccine 2010 Aug 29;28(35):5653-6. Epub 2010 Jun 29.

Unité Zoonoses Bactériennes, Agence Française de Sécurité Sanitaire des Aliments (Lerpaz), 23 Avenue du Général de Gaulle, 94706 Maisons-Alfort Cedex, France.

Comparative genomic analysis of a wild-type strain of the ovine pathogen Chlamydophila abortus and its nitrosoguanidine-induced, temperature-sensitive and virulence-attenuated live vaccine derivative identified point mutations unique to the mutant (Burall et al. [1]). Here, we evaluate the capacity of some of these mutations to either create or eliminate restriction sites using the wild-type strain C. abortus S26/3 as a reference. Three of eight genomic sites with confirmed point mutations (CAB153, CAB636 and CAB648) were retained for analysis as each resulted in the loss of a restriction site in the genome sequence of the vaccine strain. PCR-restriction fragment length polymorphism analysis using restriction enzymes chosen to specifically target the three genomic sites was then applied to a large number of C. abortus field isolates and reference strains. Our results indicate that the three mutations are uniquely present in the vaccine strain, and as such provide easy-to-use markers for the differential identification of the vaccine strain and wild-type isolates.
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http://dx.doi.org/10.1016/j.vaccine.2010.06.064DOI Listing
August 2010

Variable expression of surface-exposed polymorphic membrane proteins in in vitro-grown Chlamydia trachomatis.

Cell Microbiol 2010 Feb 6;12(2):174-87. Epub 2009 Oct 6.

Department of Microbial Pathogenesis, University of Maryland Dental School, 650 West Baltimore Street, Baltimore, MD 21201, USA.

The hypothesized variable expression of polymorphic membrane proteins (PmpA-PmpI) in Chlamydia trachomatis-infected patients was tested by examination of the expression of each Pmp subtype in in vitro-grown C. trachomatis. A panel of monospecific polyclonal and monoclonal antibodies was used to demonstrate surface exposure of Pmps of each subtype by differential immunofluorescence (IF) with and without prior detergent permeabilization of paraformaldehyde-fixed inclusions and for selected Pmps by immunogold labelling. Although specific transcript was detected for each pmp gene late in development, IF experiments with Pmp subtype-specific antibodies reveal that a number of inclusions in a single infection do not express Pmps of a given subtype. Coexpression experiments suggest that pmp genes are shut off independently from one another in non-expressing inclusions, i.e. different inclusions are switched off for different Pmps. Overall, these studies establish the existence of an efficient shutoff mechanism independently affecting the expression of each member of the pmp gene family in in vitro-grown C. trachomatis. Like other paralogous gene families of bacterial pathogens, the pmp gene family of C. trachomatis may serve the critical dual function of a highly adaptable virulence factor also providing antigenic diversity in the face of the host adaptive immune response.
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http://dx.doi.org/10.1111/j.1462-5822.2009.01389.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3073146PMC
February 2010

Kinematics of intracellular chlamydiae provide evidence for contact-dependent development.

J Bacteriol 2009 Sep 19;191(18):5734-42. Epub 2009 Jun 19.

National Centre in HIV Epidemiology and Clinical Research, Faculty of Medicine, University of New South Wales, Level 2, 376 Victoria Street, Darlinghurst, Sydney, NSW 2010, Australia.

A crucial process of chlamydial development involves differentiation of the replicative reticulate body (RB) into the infectious elementary body (EB). We present experimental evidence to provide support for a contact-dependent hypothesis for explaining the trigger involved in differentiation. We recorded live-imaging of Chlamydia trachomatis-infected McCoy cells at key times during development and tracked the temporospatial trajectories of individual chlamydial particles. We found that movement of the particles is related to development. Early to mid-developmental stages involved slight wobbling of RBs. The average speed of particles increased sharply at 24 h postinfection (after the estimated onset of RB to EB differentiation). We also investigated a penicillin-supplemented culture containing EBs, RBs, and aberrantly enlarged, stressed chlamydiae. Near-immobile enlarged particles are consistent with their continued tethering to the chlamydial inclusion membrane (CIM). We found a significantly negative, nonlinear association between speed and size/type of particles, providing further support for the hypothesis that particles become untethered near the onset of RB to EB differentiation. This study establishes the relationship between the motion properties of the chlamydiae and developmental stages, whereby wobbling RBs gradually lose contact with the CIM, and RB detachment from the CIM is coincidental with the onset of late differentiation.
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http://dx.doi.org/10.1128/JB.00293-09DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2737980PMC
September 2009

Chlamydia trachomatis-infected patients display variable antibody profiles against the nine-member polymorphic membrane protein family.

Infect Immun 2009 Aug 1;77(8):3218-26. Epub 2009 Jun 1.

Department of Microbial Pathogenesis, University of Maryland Dental School, Baltimore, 21201, USA.

Genomic analysis of the Chlamydiaceae has revealed a multigene family encoding large, putatively autotransported polymorphic membrane proteins (Pmps) with nine members in the sexually transmitted pathogen Chlamydia trachomatis. While various pathogenesis-related functions are emerging for the Pmps, observed genotypic and phenotypic variation among several chlamydial Pmps in various Chlamydia species has led us to hypothesize that the pmp gene repertoire is the basis of a previously undetected mechanism of antigenic variation. To test this hypothesis, we chose to examine the serologic response of C. trachomatis-infected patients to each Pmp subtype. Immune serum samples were collected from four populations of patients with confirmed C. trachomatis genital infection: 40 women with pelvic inflammatory disease from Pittsburgh, PA; 27 and 34 adolescent/young females from Oakland, CA, and Little Rock, AR, respectively; and 58 adult male patients from Baltimore, MD. The Pmp-specific antibody response was obtained using immunoblot analysis against each of the nine recombinantly expressed Pmps and quantified by densitometry. Our results show that nearly all C. trachomatis-infected patients mount a strong serologic response against individual or multiple Pmp subtypes and that the antibody specificity profile varies between patients. Moreover, our analysis reveals differences in the strengths and specificities of the Pmp subtype-specific antibody reactivity relating to gender and clinical outcome. Overall, our results indicate that the Pmps elicit various serologic responses in C. trachomatis-infected patients and are consistent with the pmp gene family being the basis of a mechanism of antigenic variation.
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http://dx.doi.org/10.1128/IAI.01566-08DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2715660PMC
August 2009

Ocular pathologic response elicited by Chlamydia organisms and the predictive value of quantitative modeling.

J Infect Dis 2009 Jun;199(12):1780-9

National Centre in HIV Epidemiology and Clinical Research, The University of New South Wales, Sydney, New South Wales, Australia.

Background: Chlamydia organisms are a significant cause of ocular and genital tract disease worldwide. Acute inflammatory responses are largely responsible for pathologic changes.

Methods: Guinea pigs were inoculated in the conjunctiva with various infectious doses of Chlamydia caviae. We developed a predictive model and thresholds of the ocular pathologic response, on the basis of measurements of the pathologic response and chlamydial inclusion-forming unit (ifu) loads, using statistical and mathematical techniques. We validated the predictions by modifying the pathologic response with the use of a lytic chlamydiaphage.

Results: If the area under the inclusion-forming unit curve reaches approximately 4x10(5) "ifu-days," then it is likely that an ocular pathologic response will develop and that a serious pathologic finding can develop quickly. The earlier that a pathologic response arises, the longer it will remain. A 2-log10 reduction in the peak inclusion-forming unit load reduces the chance of any pathologic finding emerging from 81% to 32%, and it reduces the chance of a serious pathologic finding emerging from 33% to 2%. A reduction in the peak chlamydial load also substantially reduces the duration of the pathologic response.

Conclusions: Our predictive model can be used to evaluate the likely effect of interventions that modify the course of chlamydial infection. It suggests that, to be effective in preventing or mitigating pathologic responses, an intervention is required to change the chlamydial time course before the peak inclusion-forming unit load is reached.
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http://dx.doi.org/10.1086/599093DOI Listing
June 2009

Divergence without difference: phylogenetics and taxonomy of Chlamydia resolved.

FEMS Immunol Med Microbiol 2009 Mar;55(2):115-9

University of California, Berkeley, USA.

Members of Chlamydiaceae have been extensively characterized by complete genome sequencing. This information provides new understanding concerning their natural evolutionary history. Comparative genome analysis is consistent with the conclusion that host-divergent strains of Chlamydiae are closely related biologically and ecologically. The previous taxonomic separation of the genus based on ribosomal sequences is neither consistent with the natural history of the organism revealed by genome comparisons, nor widely used by the Chlamydia research community 8 years after its introduction; thus, it is proposed to reunite the Chlamydiaceae into a single genus, Chlamydia.
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http://dx.doi.org/10.1111/j.1574-695X.2008.00516.xDOI Listing
March 2009

Effect of Chlamydiaphage phiCPG1 on the course of conjunctival infection with "Chlamydia caviae" in guinea pigs.

Infect Immun 2009 Mar 12;77(3):1216-21. Epub 2009 Jan 12.

Departments of Microbiology and Immunology, University of Arkansas for Medical Sciences and Arkansas Children's Hospital Research Institute, Little Rock, Arkansas 72202, USA.

Over the last several years, four different phages of chlamydiae, in addition to a phage associated with Chlamydia psittaci isolated from an ornithosis infection in ducks over 25 years ago, have been described and characterized. While these phages and their chlamydial host specificities have been characterized in vitro, there is virtually nothing known about the interaction of the phage with chlamydiae in their natural animal host. phiCPG1 is a lytic phage specific for "Chlamydia caviae," which is a natural parasite of the guinea pig. In this study, guinea pigs were inoculated in the conjunctiva with suspensions of phiCPG1 and C. caviae and the effect on the development of pathology and on the course of chlamydial infection in the conjunctiva was determined. The presence of phage delayed the appearance of the peak level of chlamydiae in the animal and decreased the pathological response. Evidence for replication of the phage in C. caviae in the conjunctival tissue was observed. Modifying the ratio of phage to chlamydiae altered the course of infection and affected phage replication. There was no evidence for the phage increasing the virulence of C. caviae infection.
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http://dx.doi.org/10.1128/IAI.01109-08DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2643638PMC
March 2009
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