Development of a real-time PCR for the specific detection of Waddlia chondrophila in clinical samples

Pharmacophore modelling based virtual screening and molecular dynamics identified the novel inhibitors and drug targets against Waddlia chondrophila

Waddlia chondrophila is a possible cause of fetal death in humans. This Chlamydia-related bacterium is an emergent pathogen that causes human miscarriages and ruminant abortions, which results in financial losses. Despite the years of efforts, the underlying mechanism behind the pathogenesis of W. chondrophila is little known which hindered the development of novel treatment options. In the framework of current study, computational approaches were used to identify novel inhibitors (phytocompounds) and drug targets against W. chondrophila. At first, RNA polymerase sigma factor SigA and 3-deoxy-D-manno-octulosonic acid transferase were identified through subtractive proteomics pipeline. Afterwards, extensive docking and simulation analyses were conducted to optimize potentially novel phytocompounds by assessing their binding affinity to target proteins. A 100ns molecular dynamics simulation well complimented the compound's binding affinity and indicated strong stability of predicted compounds at the docked site. The calculation of binding free energies with MMGBSA corroborated the significant binding affinity between phytocompounds and target protein binding sites. The proposed phytocompounds may be a viable treatment option for patients infected with W. chondrophila; however, further research is required to ensure their safety.

The role of chlamydiales in adverse pregnancy outcome: a community-based nested case-control study

OBJECTIVES

Over the last decades, the Chlamydiales order has expanded and a new group of Chlamydia-related bacteria has emerged, covering species like Waddlia (W.) chondrophila associated with bovine abortion. However, it is unknown whether they compromise human reproduction like Chlamydia (C.) trachomatis. We therefore aimed to investigate the association between vaginal colonisation of selected species of the Chlamydiales order with spontaneous abortion, preterm birth, and, animal exposure.

METHODS

Pregnant women were enrolled at the nuchal translucency scan or when admitted for suspected miscarriage at Aarhus University Hospital, Denmark. Cases were defined as spontaneous abortion <22 weeks and preterm birth <37 weeks. Controls were defined as term birth ≥37 weeks. Vaginal samples from 1203 women were assessed using C.trachomatis, W.chondrophila and pan-Chlamydiales specific real-time PCRs targeting the 16S rRNA gene.

RESULTS

A total of 1120 women of primarily Caucasian ancestry were enrolled, including 193 spontaneous abortions, 88 preterm births, and 839 term births. After sequencing for verification, the prevalence of Chlamydiales was 3/193 (1.6%, 95%CI 0.5-4.8) in women experiencing spontaneous abortion, 2/88 (2.3%, 95%CI 0.6-8.9) in women with preterm birth, and 20/839 (2.4%, 95%CI 1.6-3.7) in women giving birth at term. Thus, Chlamydiales infection was neither significantly associated with spontaneous abortion (OR 0.68, 95%CI 0.15-2.01) nor preterm birth (OR 1.02, 95%CI 0.15-3.60) compared to women giving birth at term. Amplicons from the pan-Chlamydiales assay revealed close sequence homology and were primarily identified as uncultured Chlamydiales bacteria.

CONCLUSIONS

Among Danish pregnant women, the prevalence of Chlamydiales was low and not associated with adverse pregnancy outcomes.

Development of a duplex q-PCR for the simultaneous detection of Parachlamydia acanthamoebae and Simkania negevensis in environmental and clinical samples

Parachlamydia acanthamoebae and Simkania negevensis, two Chlamydia-like bacteria, have been recently recognized as emerging human respiratory pathogens. The prevalence and frequency of these bacteria in the environment and among atypical pneumonia patients are still underestimated by classical cultures, immunohistochemistry and serology which are non-specific, long and tedious methods. This study aims to develop a new duplex probe-based q-PCR assay for the simultaneous detection and quantification of P. acanthamoebae and S. negevensis. The selected hydrolysis probes displayed no cross-reaction with the closely related Chlamydia or the other tested waterborne pathogens. The assay achieved a large dynamic range for quantification (from 5 × 10⁶ to 5 DNA copies/reaction). Efficiencies of FAM and JOE label probes weren't affected when they were combined. They were close to 100%, indicating the linear amplification. The application of this diagnostic tool resulted in 9/47 (19%) and 4/47 (8.5%) positive water samples for P. acanthamoebae and S. negevensis, respectively. P. acanthamoebae was also covered from 2/78 (2.5%) respiratory specimens and only one case (1/200 = 0.5%) of P. acanthamoebae and SARS-CoV-2 co-infection was noticed. While S. negevensis wasn't detected in clinical samples, the developed duplex q-PCR was shown to be an accurate, highly sensitive, and robust diagnostic tool for the detection and quantification of P. acanthamoebae and S. negevensis.

Optimization and Application of Real-Time qPCR Assays in Detection and Identification of Chlamydiales in Products of Domestic Ruminant Abortion

Domestic ruminant abortions due to infectious agents represent an important cause of economic losses in the agricultural industry. This study aimed to optimise and apply qPCR assays for detection of Chlamydiales in domestic ruminant abortion cases. Primers and probes for detection of the order Chlamydiales, Chlamydia abortus, Chlamydia pecorum, Parachlamydia acanthamoeba and Waddlia chondrophila were taken from the literature to create one singleplex and two duplex assays and the assays were optimised. Placentitis and pneumonia are pathological lesions associated with Chlamydiales infection. In a previous study, twenty-five clinical cases had pathological lesions of placentitis or pneumonia. These cases were investigated further by application of the qPCR assays in this study. Chlamydiales were detected in 16 cases. C. abortus, P. acanthamoeba and W. chondrophila were detected in bovine; and C. pecorum and W. chondrophila in ovine and caprine cases. Chlamydiales were detected in three previously inconclusive cases. Identification was improved from genus to species level (C. pecorum). Four cases remained inconclusive. In conclusion, detection of Chlamydiales and differentiation to species level was improved. This study reports the first detection of P. acanthamoeba and W. chondrophila in abortion cases in South Africa, indicating a potentially significant role in abortions in this country.

A new TaqMan real-time PCR assay to detect Parachlamydia acanthamoebae and to monitor its co-existence with SARS-COV-2 among COVID-19 patients

Human respiratory infections caused by a large variety of microbial pathogens are the most common diseases responsible for hospitalization, morbidity and mortality. Parachlamydia acanthamoebae, a Chlamydia-related bacterium, has been found to be potentially associated with these diseases. An early and accurate diagnosis of this pathogen could be useful to avoid the potential respiratory complications linked especially to COVID-19 patients and to set suitable outbreak control measures. A TaqMan-PCR assay was developed to detect and quantify Parachlamydia acanthamoebae in environmental and clinical samples from patients of all ages with COVID-19. The selected hydrolysis probe displayed no cross-reaction with the closely related Chlamydia or the other tested pathogens. This q-PCR achieved good reproducibility and repeatability with a detection limit of about 5 DNA copies per reaction. Using this q-PCR assay, Parachlamydia acanthamoebae was detected in 2/78 respiratory specimens and 9/47 water samples. Only one case (1.3%) of Parachlamydia acanthamoebae and SARS-COV-2 co-infection was noticed. To our knowledge, the combination of these two respiratory pathogens has not been described yet. This new TaqMan-PCR assay represents an efficient diagnostic tool to survey Parachlamydia acanthamoebae on a large-scale screening programs and also during outbreaks.

Subtractive proteomics approach to Unravel the druggable proteins of the emerging pathogen Waddlia chondrophila and drug repositioning on its MurB protein

Waddlia chondrophila is an emerging pathogen that has been implicated in numerous unpropitious pregnancy events in humans and ruminants. Taking into account its association with abortigenic events, possible modes of transmission, and future risk, immediate clinical measures are required to prevent widespread damage caused by this organism and hence this study. Here, a subtractive proteomics approach was employed to identify druggable proteins of W. chondrophila. Considering the essential genes, antibiotic resistance proteins, and virulence factors, 676 unique important proteins were initially identified for this bacterium. Afterward, NCBI BLASTp performed against human proteome identified 223 proteins that were further pushed into KEGG Automatic Annotation Server (KAAS) for automatic annotation. Using the information from the Kyoto Encyclopedia of Genes and Genomes (KEGG) database 14 Waddlia specific metabolic pathways were identified with respect to humans. Analyzing the data from KAAS and KEGG databases, forty-eight metabolic pathway-dependent, and seventy metabolic pathway independent proteins were identified. Standalone BLAST search against DrugBank FDA approved drug targets revealed eight proteins that are finally considered druggable proteins. Prediction of three-dimensional structures was done for the eight proteins through homology modeling and the Ramachandran plot model showed six models as a valid prediction. Finally, virtual screening against MurB protein was performed using FDA approved drugs to employ the drug repositioning strategy. Three drugs showed promising docking results that can be used for therapeutic purposes against W. chondrophila following the clinical validation of the study.

COVID-19: Diagnostics, Therapeutic Advances, and Vaccine Development

Purpose of Review

Human race is currently facing the wrath of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a highly transmittable and pathogenic RNA virus, causing coronavirus disease 2019 (COVID-19), the worst ever global pandemic. Coronaviruses (CoVs) have emerged as a major public health concern. Urgent global response to COVID-19 outbreak has been to limit spread of SARS-CoV-2 via extensive monitoring and containment. Various treatment regimens have been adopted to manage COVID-19, with known drugs and drug combinations used to decrease the morbidity and mortality associated with COVID-19. Intensive research on various fronts including studying molecular and structural aspects of these viruses and unraveling the pathophysiology and mechanistic basis of COVID-19 aimed at developing effective prophylactic, therapeutic agents and vaccines has been carried out globally.

Recent Findings

No approved antiviral treatment except remdesivir exists for SARS-CoV-2 till date though novel drug targets have been identified. However, worldwide frantic and competitive vaccine development pharmaceutical race has borne fruit in the form of a number of promising candidate vaccines, out of which few have already received emergency use authorization by regulatory bodies in record time.

Summary

This review highlights the painstaking efforts of healthcare workers and scientific community to successfully address the COVID-19 pandemic—though damage in the form of severe illness, loss of lives, and livelihood has left a serious mark. Focusing on extensive research on various therapeutic options and antiviral strategies including neutralizing antibodies, potential drugs, and drug targets, light has been shed on various diagnostic options and the amazing vaccine development process as well.

Transcriptional Landscape of Waddlia chondrophila Aberrant Bodies Induced by Iron Starvation

Chronic infections caused by obligate intracellular bacteria belonging to the Chlamydiales order are related to the formation of persistent developmental forms called aberrant bodies (ABs), which undergo DNA replication without cell division. These enlarged bacteria develop and persist upon exposure to different stressful conditions such as β-lactam antibiotics, iron deprivation and interferon-γ. However, the mechanisms behind ABs biogenesis remain uncharted. Using an RNA-sequencing approach, we compared the transcriptional profile of ABs induced by iron starvation to untreated bacteria in the Chlamydia-related species Waddliachondrophila, a potential agent of abortion in ruminants and miscarriage in humans. Consistent with the growth arrest observed following iron depletion, our results indicate a significant reduction in the expression of genes related to energy production, carbohydrate and amino acid metabolism and cell wall/envelope biogenesis, compared to untreated, actively replicating bacteria. Conversely, three putative toxin-antitoxin modules were among the most up-regulated genes upon iron starvation, suggesting that their activation might be involved in growth arrest in adverse conditions, an uncommon feature in obligate intracellular bacteria. Our work represents the first complete transcriptomic profile of a Chlamydia-related species in stressful conditions and sets the grounds for further investigations on the mechanisms underlying chlamydial persistence.

Evaluations of the serological test in the diagnosis of 2019 novel coronavirus (SARS-CoV-2) infections during the COVID-19 outbreak

We developed a chemiluminescence immunoassay method based on the recombinant nucleocapsid antigen and assessed its performance for the clinical diagnosis of severe acute respiratory syndrome coronavirus (SARS-CoV)-2 infections by detecting SARS-CoV-2–specific IgM and IgG antibodies in patients. Full-length recombinant nucleocapsid antigen and tosyl magnetic beads were used to develop the chemiluminescence immunoassay approach. Plasmas from 29 healthy cohorts, 51 tuberculosis patients, and 79 confirmed SARS-CoV-2 patients were employed to evaluate the chemiluminescence immunoassay method performance for the clinical diagnosis of SARS-CoV-2 infections. A commercial ELISA kit (Darui Biotech, China) using the same nucleocapsid antigen was used for the in-parallel comparison with our chemiluminescence immunoassay method. The IgM and IgG manner of testing in the chemiluminescence immunoassay method showed a sensitivity and specificity of 60.76% (95% CI 49.1 to 71.6) and 92.25% (95% CI 83.4 to 97.2) and 82.28% (95% CI 72.1 to 90.0) and 97.5% (95% CI 91.3 to 99.7), respectively. Higher sensitivity and specificity were observed in the chemiluminescence immunoassay method compared with the Darui Biotech ELISA kit. The developed high sensitivity and specificity chemiluminescence immunoassay IgG testing method combined with the RT-PCR approach can improve the clinical diagnosis for SARS-CoV-2 infections and thus contribute to the control of COVID-19 expansion.

Eukaryotic Cell Permeabilisation to Identify New Putative Chlamydial Type III Secretion System Effectors Secreted within Host Cell Cytoplasm

Chlamydia trachomatis and Waddlia chondrophila are strict intracellular bacteria belonging to the Chlamydiales order. C. trachomatis is the most frequent bacterial cause of genital and ocular infections whereas W. chondrophila is an opportunistic pathogen associated with adverse pregnancy outcomes and respiratory infections. Being strictly intracellular, these bacteria are engaged in a complex interplay with their hosts to modulate their environment and create optimal conditions for completing their life cycle. For this purpose, they possess several secretion pathways and, in particular, a Type III Secretion System (T3SS) devoted to the delivery of effector proteins in the host cell cytosol. Identifying these effectors is a crucial step in understanding the molecular basis of bacterial pathogenesis. Following incubation of infected cells with perfringolysin O, a pore-forming toxin that binds cholesterol present in plasma membranes, we analysed by mass spectrometry the protein content of the host cell cytoplasm. We identified 13 putative effectors secreted by C. trachomatis and 19 secreted by W. chondrophila. Using Y. enterocolitica as a heterologous expression and secretion system, we confirmed that four of these identified proteins are secreted by the T3SS. Two W. chondrophila T3SS effectors (hypothetical proteins Wcw_0499 and Wcw_1706) were further characterised and demonstrated to be early/mid-cycle effectors. In addition, Wcw_1706 is associated with a tetratricopeptide domain-containing protein homologous to C. trachomatis class II chaperone. Furthermore, we identified a novel C. trachomatis effector, CT460 that localises in the eukaryotic nucleus when ectopically expressed in 293 T cells.

Waddlia chondrophila and Male Infertility

Waddlia chondrophila, a Chlamydia-like bacterium, has been previously associated with adverse pregnancy outcomes. Analogously to Chlamydia trachomatis, W. chondrophila also negatively impacts human semen and may be a source of impaired male fertility. In this study, we analyzed W. chondrophila seroprevalence in a population of male patients of infertile couples and the impact of past exposition to this bacterium on semen parameters. Our results show a surprisingly high seroprevalence of W. chondrophila, which contrasts with a previous study focusing on a population of healthy men. Nevertheless, we did not observe any significant association between positive serology and abnormal sperm parameters. This may suggest that a negative impact on semen is observed only during an ongoing infection. Alternatively, W. chondrophila may have an immune impact on male fertility, as previously postulated for women with adverse pregnancy outcomes.

Diverse Stress-Inducing Treatments cause Distinct Aberrant Body Morphologies in the Chlamydia-Related Bacterium, Waddlia chondrophila

Chlamydiae, such as Chlamydia trachomatis and Chlamydia pneumoniae, can cause chronic infections. It is believed that persistent forms called aberrant bodies (ABs) might be involved in this process. AB formation seems to be a common trait of all members of the Chlamydiales order and is caused by distinct stress stimuli, such as β-lactam antibiotics or nutrient starvation. While the diverse stimuli inducing ABs are well described, no comprehensive morphological characterization has been performed in Chlamydiales up to now. We thus infected mammalian cells with the Chlamydia-related bacterium Waddlia chondrophila and induced AB formation using different stimuli. Their morphology, differences in DNA content and in gene expression were assessed by immunofluorescence, quantitative PCR, and reverse transcription PCR, respectively. All stimuli induced AB formation. Interestingly, we show here for the first time that the DNA gyrase inhibitor novobiocin also caused appearance of ABs. Two distinct patterns of ABs could be defined, according to their morphology and number: (i) small and multiple ABs versus (ii) large and rare ABs. DNA replication of W. chondrophila was generally not affected by the different treatments. Finally, no correlation could be observed between specific types of ABs and expression patterns of mreB and rodZ genes.

A predation assay using amoebae to screen for virulence factors unearthed the first W. chondrophila inclusion membrane protein

Waddlia chondrophila is an intracellular bacterium phylogenetically related to the well-studied human and animal pathogens of the Chlamydiaceae family. In the last decade, W. chondrophila was convincingly demonstrated to be associated with adverse pregnancy outcomes in humans and abortions in animals. All members of the phylum Chlamydiae possess a Type Three Secretion System that they use for delivering virulence proteins into the host cell cytosol to modulate their environment and create optimal conditions to complete their life cycle. To identify W. chondrophila virulence proteins, we used an original screening approach that combines a cosmid library with an assay monitoring resistance to predation by phagocytic amoebae. This technique combined with bioinformatic data allowed the identification of 28 candidate virulence proteins, including Wimp1, the first identified inclusion membrane protein of W. chondrophila.

Limited presence of Waddlia chondrophila in drinking water systems in the Netherlands

Waddlia chondrophila is an emerging pathogen belonging to the order of Chlamydiales. This obligate intracellular bacterium was initially isolated from an aborted bovine fetus and is associated with adverse pregnancy outcomes in women. The ability of W. chondrophila to reside and replicate within a range of free-living amoebae implies a possible widespread environmental presence. Potential hosts of W. chondrophila are present in Dutch drinking water. This study therefore investigated the presence of W. chondrophila DNA in drinking water by analysing 59 samples from ten drinking water systems throughout the Netherlands. Samples were taken at three distances from the treatment plant, during both summer and winter. Twelve of the samples were positive, originating from two of the treatment plants, of which three samples were quantifiable.

Interactions Screenings Unearth Potential New Divisome Components in the Chlamydia-Related Bacterium, Waddlia chondrophila

Chlamydiales order members are obligate intracellular bacteria, dividing by binary fission. However, Chlamydiales lack the otherwise conserved homologue of the bacterial division organizer FtsZ and certain division protein homologues. FtsZ might be functionally replaced in Chlamydiales by the actin homologue MreB. RodZ, the membrane anchor of MreB, localizes early at the division septum. In order to better characterize the organization of the chlamydial divisome, we performed co-immunoprecipitations and yeast-two hybrid assays to study the interactome of RodZ, using Waddlia chondrophila, a potentially pathogenic Chlamydia-related bacterium, as a model organism. Three potential interactors were further investigated: SecA, FtsH, and SufD. The gene and protein expression profiles of these three genes were measured and are comparable with recently described division proteins. Moreover, SecA, FtsH, and SufD all showed a peripheral localization, consistent with putative inner membrane localization and interaction with RodZ. Notably, heterologous overexpression of the abovementioned proteins could not complement E. coli mutants, indicating that these proteins might play different functions in these two bacteria or that important regulators are not conserved. Altogether, this study brings new insights to the composition of the chlamydial divisome and points to links between protein secretion, degradation, iron homeostasis, and chlamydial division.

Impact of Waddlia chondrophila infection on pregnancy in the mouse

The intracellular bacterium Waddlia chondrophila, which belongs to the Chlamydiales order, was found to be associated with miscarriage in humans. There is little to no knowledge regarding the mode of infection, impact on the neonate and pathophysiology of this emerging bacterium. We have previously shown that W. chondrophila induces a systemic infection, organ pathology and elicits T helper type 1-associated humoral immunity in a murine model of genital infection. In the present study, we took advantage of this model of infection to evaluate the impact of this bacterium on the mouse pregnancy. We used two routes of inoculation, vaginal and intrauterine, to introduce infection before and after mating. Our results show that genital infection by W. chondrophila did not have any significant impact on gestation length and maternal weight gain, nor on the number of offspring and their weight. This observation indicates that the mouse model of infection is not suitable to study the effect of W. chondrophila on pregnancy and alternative models of infection, including in vitro ones, should be used. Moreover, an indirect immunopathological mechanism activated by this bacterium should be further explored.

A SpoIID Homolog Cleaves Glycan Strands at the Chlamydial Division Septum

Chlamydiales species are obligate intracellular bacteria and important human pathogens that have a minimal division machinery lacking the proteins that are essential for bacterial division in other species, such as FtsZ. Chlamydial division requires synthesis of peptidoglycan, which forms a ring at the division septum and is rapidly turned over. However, little is known of peptidoglycan degradation, because many peptidoglycan-degrading enzymes are not encoded by chlamydial genomes. Here we show that an homologue of SpoIID, a peptidoglycan-degrading enzyme involved in sporulation of bacteria such as Bacillus subtilis, is expressed in Chlamydiales, localizes at the division septum, and degrades peptidoglycan in vitro, indicating that SpoIID is not only involved in sporulation but also likely implicated in division of some bacteria.

Chlamydiales species are obligate intracellular bacteria lacking a classical peptidoglycan sacculus but relying on peptidoglycan synthesis for cytokinesis. While septal peptidoglycan biosynthesis seems to be regulated by MreB actin and its membrane anchor RodZ rather than FtsZ tubulin in Chlamydiales, the mechanism of peptidoglycan remodeling is poorly understood. An amidase conserved in Chlamydiales is able to cleave peptide stems in peptidoglycan, but it is not clear how peptidoglycan glycan strands are cleaved since no classical lytic transglycosylase is encoded in chlamydial genomes. However, a protein containing a SpoIID domain, known to possess transglycosylase activity in Bacillus subtilis, is conserved in Chlamydiales. We show here that the SpoIID homologue of the Chlamydia-related pathogen Waddlia chondrophila is a septal peptidoglycan-binding protein. Moreover, we demonstrate that SpoIID acts as a lytic transglycosylase on peptidoglycan and as a muramidase on denuded glycan strands in vitro. As SpoIID-like proteins are widespread in nonsporulating bacteria, SpoIID might commonly be a septal peptidoglycan remodeling protein in bacteria, including obligate intracellular pathogens, and thus might represent a promising drug target.

Parachlamydia acanthamoebae Detected during a Pneumonia Outbreak in Southeastern Finland, in 2017⁻2018

Community-acquired pneumonia (CAP) is a common disease responsible for significant morbidity and mortality. However, the definite etiology of CAP often remains unresolved, suggesting that unknown agents of pneumonia remain to be identified. The recently discovered members of the order Chlamydiales, Chlamydia-related bacteria (CRB), are considered as possible emerging agents of CAP. Parachlamydia acanthamoebae is the most studied candidate. It survives and replicates inside free-living amoeba, which it might potentially use as a vehicle to infect animals and humans. A Mycoplasma pneumoniae outbreak was observed in Kymenlaakso region in Southeastern Finland during August 2017-January 2018. We determined the occurrence of Chlamydiales bacteria and their natural host, free-living amoeba in respiratory specimens collected during this outbreak with molecular methods. Altogether, 22/278 (7.9%) of the samples contained Chlamydiales DNA. By sequence analysis, majority of the CRBs detected were members of the Parachlamydiaceae family. Amoebal DNA was not detected within the sample material. Our study further proposes that Parachlamydiaceae could be a potential agent causing atypical CAP in children and adolescents.

Identification of new DNA-associated proteins from Waddlia chondrophila

Transcriptional regulation in Chlamydiae is still poorly understood. The absence until recently of genetic tools is the main cause of this gap. We discovered three new potential DNA-associated proteins of Waddlia chondrophila, a Chlamydia-related bacterium, using heparin chromatography coupled to mass spectrometry (Wcw_0377, Wcw_1456, and Wcw_1460). By ChIP-seq analysis, we determined the regulatory landscape of these three proteins and we showed that Wcw_0377 binds all along the genome whereas Wcw_1456 and _1460 possess a wide regulon with a large number of co-regulated genes. Wcw_1456 and Wcw_1460 interact with RpoD (σ⁶⁶), emerging as potential RpoD regulators. On the other hand, Wcw_0377 is able to reach the host nucleus, where it might interact with eukaryotic histones through its putative chromatin-remodelling SWIB/MDM2 domain.

Waddlia chondrophila, a Chlamydia-related bacterium, has a negative impact on human spermatozoa

STUDY QUESTION

What is the impact of Waddlia chondrophila, an emerging Chlamydia-related bacterium associated with miscarriage, on human spermatozoa?

SUMMARY ANSWER

W. chondrophila had a negative impact on human spermatozoa (decrease in viability and mitochondrial membrane potential) and was not entirely removed from infected samples by density gradient centrifugation.

WHAT IS KNOWN ALREADY

Bacterial infection or colonization might have a deleterious effect on male fertility. Waddlia chondrophila was previously associated with miscarriage, but its impact on male reproductive function has never been studied.

STUDY DESIGN SIZE, DURATION

An in vitro model of human spermatozoa infection was used to assess the effects of W. chondrophila infection. Controls included Chlamydia trachomatis serovar D and latex beads with similar size to bacteria.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Purified motile spermatozoa were infected with W. chondrophila (multiplicity of infection of 1). Immunohistochemistry combined with confocal microscopy was used to evaluate how bacteria interact with spermatozoa. The impact on physiology was assessed by monitoring cell viability, mitochondrial membrane potential and DNA fragmentation.

MAIN RESULTS AND THE ROLE OF CHANCE

Using super-resolution confocal microscopy, bacteria were localized on spermatozoa surface, as well as inside the cytoplasm. Compared to controls, W. chondrophila caused a 20% increase in mortality over 72 h of incubation (P < 0.05). Moreover, higher bacterial loads significantly reduced mitochondrial membrane potential. Bacteria present on spermatozoa surface were able to further infect a cell-monolayer, indicating that sperm might vector bacteria during sexual intercourse.

LIMITATIONS REASONS FOR CAUTION

The main limitation of the study is the use of an in vitro model of infection, which might be too simplistic compared to an actual infection. An animal model of infection should be developed to better evaluate the in vivo impact of W. chondrophila.

WIDER IMPLICATIONS OF THE FINDINGS

Intracellular bacteria, including C. trachomatis, Mycoplasma spp. and Ureaplasma spp., are associated with male infertility. Waddlia chondrophila might represent yet another member of this group, highlighting the need for more rigorous microbiological analysis during investigations for male infertility.

STUDY FUNDING/COMPETING INTEREST(S)

This work has been funded by the Department of Obstetrics and Gynecology, Lausanne University Hospital, Switzerland, and by the Swiss National Science Foundation (Grant nos. 310030-156169/1, 320030-169853/1 and 320030-169853/2 attributed to D.B.). D.B. is also supported by the 'Fondation Leenaards' through the 'Bourse pour la relève académique', by the 'Fondation Divesa' and by the 'Loterie Romande'. No conflicts of interest to declare.

Virulence-related comparative transcriptomics of infectious and non-infectious chlamydial particles

BACKGROUND

Members of the phylum Chlamydiae are obligate intracellular pathogens of humans and animals and have a serious impact on host health. They comprise several zoonotic species with varying disease outcomes and prevalence. To investigate differences in virulence, we focused on Chlamydia psittaci, C. abortus and Waddlia chondrophila. Most threatening is C. psittaci, which frequently infects humans and causes psittacosis associated with severe pneumonia. The closest relative of C. psittaci is C. abortus, which shares the vast majority of genes but less frequently infects humans, and causes stillbirth and sepsis. W. chondrophila is more distantly related, and occasional human infections are associated with respiratory diseases or miscarriage. One possible explanation for differences in virulence originate from species-specific genes as well as differentially expressed homologous virulence factors.

RESULTS

RNA-sequencing (RNA-Seq) was applied to purified infectious elementary bodies (EBs) and non-infectious reticulate bodies (RBs) in order to elucidate the transcriptome of the infectious and replicative chlamydial states. The results showed that approximately half of all genes were differentially expressed. For a descriptive comparison, genes were categorised according to their function in the RAST database. This list was extended by the inclusion of inclusion membrane proteins, outer membrane proteins, polymorphic membrane proteins and type III secretion system effectors. In addition, the expression of fifty-six known and a variety of predicted virulence and immunogenic factors with homologs in C. psittaci, C. abortus and W. chondrophila was analysed. To confirm the RNA-Seq results, the expression of nine factors was validated using real-time quantitative polymerase chain reaction (RT-qPCR). Comparison of RNA-Seq and RT-qPCR results showed a high mean Pearson correlation coefficient of 0.95.

CONCLUSIONS

It was shown that both the replicative and infectious chlamydial state contained distinctive transcriptomes and the cellular processes emphasised in EBs and RBs differed substantially based on the chlamydial species. In addition, the very first interspecies transcriptome comparison is presented here, and the considerable differences in expression of homologous virulence factors might contribute to the differing infection rates and disease outcomes of the pathogens. The RNA-Seq results were confirmed by RT-qPCR and demonstrate the feasibility of interspecies transcriptome comparisons in chlamydia.

Presence of Waddlia chondrophila in hot water systems from non-domestic buildings in France

The presence of Waddlia chondrophila has been related to respiratory tract infections and human and animal fetal death. Although several sources of infection have been suggested, the actual source remains unknown and limited information exists on the prevalence of W. chondrophila in the environment. This pathogen has been previously detected in well water but its presence has not been confirmed in water networks. Since these bacteria have been detected in water reservoirs, it has been hypothesized that they can access artificial water systems and survive until they find appropriate conditions to proliferate. In this work, their presence in water samples from 19 non-domestic water networks was tested by quantitative polymerase chain reaction (qPCR). Approximately half of the networks (47%) were positive for W. chondrophila and the overall results revealed 20% positive samples (12/59). Furthermore, most of the samples showed low concentrations of the pathogen (<200 genomic units/L). This finding demonstrates that W. chondrophila can colonize some water networks. Therefore, they must be considered as potential infection sources in future epidemiological studies.

What is the true clinical relevance of Simkania negevensis and other emerging Chlamydiales members?

Waddlia chondrophila and Simkania negevensis are emerging Chlamydia-related bacteria. Similar to the pathogenic organisms Chlamydia pneumoniae and Chlamydia trachomatis, these emerging bacteria are implicated in human genital infections and respiratory diseases. We used a screening strategy based on a newly developed S. negevensis–specific quantitative real-time PCR (qPCR) and a pan-Chlamydiales qPCR. We could not detect S. negevensis in 458 respiratory, genitourinary, cardiac and hepatic samples tested. One urethral swab was positive for W. chondrophila. We observed a low prevalence of Chlamydiales in respiratory samples (1/200, 0.5%), which suggests that C. pneumoniae is an uncommon respiratory pathogen. Furthermore, we screened 414 human serum samples from Switzerland, England and Israel and observed a low prevalence (<1%) of exposure to S. negevensis. Conversely, humans were commonly exposed to W. chondrophila, with seroprevalences ranging from 8.6% to 32.5%. S. negevensis is not a clinically relevant pathogen, but further research investigating the role of W. chondrophila is needed.

Chlamydia trachomatis and chlamydia-like bacteria: new enemies of human pregnancies

PURPOSE OF REVIEW

This review provides an update on the roles of Chlamydia trachomatis and the related Waddlia chondrophila and Parachlamydia acanthamoebae in miscarriage, stillbirths and preterm labour in humans. A broad audience, including microbiologist, infectiologists, obstetricians and gynaecologists, should be aware of the potential threat of these Chlamydiales for human reproduction.

RECENT FINDINGS

Despite increasing laboratory techniques and possibilities to perform diagnostic tests, the cause of miscarriage is only identified in 50% of the cases. Intracellular bacteria, such as C. trachomatis and Chlamydia-related bacteria, are difficult to detect in routine clinical samples and could represent possible agents of miscarriages. C. trachomatis is considered the world largest sexual transmitted bacterial agent and is associated with adverse pregnancy outcome in human. In the last decade Chlamydia-like organisms, such as W. chondrophila and P. acanthamoebae, have also been associated with adverse pregnancy outcomes in human and/or animals.

SUMMARY

We review here the current evidences for a pathogenic role in humans, the diagnostic approaches and possible treatment options of C. trachomatis, W. chondrophila and P. acanthamoebae.

Simkania negevensis may produce long-lasting infections in human pneumocytes and endometrial cells

Simkania negevensis is a novel Chlamydia-related bacterium and the founding member of the Simkaniaceae family within the Chlamydiales order. Little is known about the biology and pathogenesis of this bacterium. So far, S. negevensis has been considered as an amoebal symbiont, but its natural host remains unknown. Moreover, evidence of human exposition has been reported worldwide and an association with pneumonia and bronchiolitis is suspected. Here, we evaluated the ability of S. negevensis to replicate in potential environmental reservoirs, namely amoebae and arthropods, as well as in mammalian cells (Vero cells, pneumocytes and endometrial cells) and further evaluated the characteristics of its replicative vacuole. We demonstrated that S. negevensis efficiently replicates in all cell lines tested, with the shortest doubling time and an increased adhesion observed in pneumocytes. Our work highlights the specificities of the Simkania-containing vacuole compared to other Chlamydiales; contrarily to Chlamydia trachomatis, S. negevensis does not disrupt the Golgi apparatus. Importantly, our work suggests that S. negevensis infection is associated with few cytopathic effects and might persist for a prolonged time in infected cells. Further evaluation of its implication in human diseases is required; an implication in chronic or subacute respiratory infections might be suspected.

Molecular prevalence of Chlamydia and Chlamydia-like bacteria in Tunisian domestic ruminant farms and their influencing risk factors

Chlamydia and Chlamydia-like bacteria are well known to infect several organisms and may cause a wide range of diseases, particularly in ruminants. To gain insight into the prevalence and diversity of these intracellular bacteria, we applied a pan-Chlamydiales real-time PCR to 1,134 veterinary samples taken from 130 Tunisian ruminant herds. The true adjusted animal population-level prevalence was 12.9% in cattle, against 8.7% in sheep. In addition, the true adjusted herd-level prevalence of Chlamydiae was 80% in cattle and 25.5% in sheep. Chlamydiales from three family-level lineages were detected indicating a high biodiversity of Chlamydiales in ruminant herds. Our results showed that Parachlamydia acanthamoebae could be responsible for bovine and ovine chlamydiosis in central-eastern Tunisia. Multivariable logistic regression analysis at the animal population level indicated that strata and digestive disorders variables were the important risk factors of bovine and ovine chlamydiosis. However, origin and age variables were found to be associated with bovine and ovine chlamydiosis, respectively. At the herd level, risk factors for Chlamydia positivity were as follows: abortion and herd size for cattle against breeding system, cleaning frequency, quarantine, use of disinfectant and floor type for sheep. Paying attention to these risk factors will help improvement of control programs against this harmful zoonotic disease.

Ten years of R&D and full automation in molecular diagnosis

A 10-year experience of our automated molecular diagnostic platform that carries out 91 different real-time PCR is described. Progresses and future perspectives in molecular diagnostic microbiology are reviewed: why automation is important; how our platform was implemented; how homemade PCRs were developed; the advantages/disadvantages of homemade PCRs, including the critical aspects of troubleshooting and the need to further reduce the turnaround time for specific samples, at least for defined clinical settings such as emergencies. The future of molecular diagnosis depends on automation, and in a novel perspective, it is time now to fully acknowledge the true contribution of molecular diagnostic and to reconsider the indication for PCR, by also using these tests as first-line assays.

A Zebrafish Model for Chlamydia Infection with the Obligate Intracellular Pathogen Waddlia chondrophila

Obligate intracellular chlamydial bacteria of the Planctomycetes-Verrucomicrobia-Chlamydiae (PVC) superphylum are important pathogens of terrestrial and marine vertebrates, yet many features of their pathogenesis and host specificity are still unknown. This is particularly true for families such as the Waddliacea which, in addition to epithelia, cellular targets for nearly all Chlamydia, can infect and replicate in macrophages, an important arm of the innate immune system or in their free-living amoebal counterparts. An ideal pathogen model system should include both host and pathogen, which led us to develop the first larval zebrafish model for chlamydial infections with Waddlia chondrophila. By varying the means and sites of application, epithelial cells of the swim bladder, endothelial cells of the vasculature and phagocytosing cells of the innate immune system became preferred targets for infection in zebrafish larvae. Through the use of transgenic zebrafish, we could observe recruitment of neutrophils to the infection site and demonstrate for the first time that W. chondrophila is taken up and replicates in these phagocytic cells and not only in macrophages. Furthermore, we present evidence that myeloid differentiation factor 88 (MyD88) mediated signaling plays a role in the innate immune reaction to W. chondrophila, eventually by Toll-like receptor (TLRs) recognition. Infected larvae with depleted levels of MyD88 showed a higher infection load and a lower survival rate compared to control fish. This work presents a new and potentially powerful non-mammalian experimental model to study the pathology of chlamydial virulence in vivo and opens up new possibilities for investigation of other members of the PVC superphylum.

Prevalence and diversity of Chlamydiales and other amoeba-resisting bacteria in domestic drinking water systems

A growing number of human infections incriminate environmental bacteria that have evolved virulent mechanisms to resist amoebae and use them as a replicative niche. These bacteria are designated amoeba-resisting bacteria (ARB). Despite the isolation of these ARB in various human clinical samples, the possible source of infection remains undetermined in most cases. However, it is known that the ARB Legionella pneumophila, for instance, causes a respiratory infection in susceptible hosts after inhalation of contaminated water aerosols from various sources. The Chlamydiales order contains many ARB, such as Parachlamydia acanthamoebae or Simkania negevensis, previously implicated in human respiratory infections with no identified contamination sources. We thus investigated whether domestic water systems are a potential source of transmission of these Chlamydiales to humans by using amoebal culture and molecular methods. Other important ARB such as mycobacteria and Legionella were also investigated, as were their possible amoebal hosts. This work reports for the first time a very high prevalence and diversity of Chlamydiales in drinking water, being detected in 35 (72.9%) of 48 investigated domestic water systems, with members of the Parachlamydiaceae family being dominantly detected. Furthermore, various Legionella and mycobacteria species were also recovered, some species of which are known to be causal agents of human infections.

Simkania negevensis, an insight into the biology and clinical importance of a novel member of the Chlamydiales order

Simkania negevensis is a Chlamydia-related bacterium discovered in 1993 and represents the founding member of the Simkaniaceae family within the Chlamydiales order. As other Chlamydiales, it is an obligate intracellular bacterium characterized by a biphasic developmental cycle. Its similarities with the pathogenic Chlamydia trachomatis and Chlamydia pneumoniae make it an interesting bacterium. So far, little is known about its biology, but S. negevensis harbors various microbiological characteristics of interest, including a strong association of the Simkania-containing vacuole with the ER and the presence of an intron in the 23S rRNA encoding gene. Evidence of human exposition has been reported worldwide. However, there is a lack of robust clinical studies evaluating its implication in human diseases; current data suggest an association with pneumonia and bronchiolitis making S. negevensis a potential emerging pathogen. Owing to its fastidious growth requirements, the clinical relevance of S. negevensis is probably underestimated. In this review, we summarize the current knowledge on S. negevensis and explore future research challenges.

Chlamydia related bacteria (Chlamydiales) in early pregnancy: community-based cohort study

Objectives

Serological case–control studies suggest that certain chlamydia-related bacteria (Chlamydiales) which cause cows to abort may do the same in humans. Chlamydiales include Waddlia chondrophila, Chlamydia abortus and Chlamydia trachomatis. Data on prevalence of Chlamydiales in pregnancy are sparse. Using stored urine samples from a carefully characterised cohort of 847 newly pregnant women recruited from 37 general practices in London, UK, we aimed to investigate the prevalence and types of Chlamydiales infections. We also explored possible associations with miscarriage or spontaneous preterm birth.

Methods

Samples were tested using W. chondrophila and pan-Chlamydiales specific real-time PCRs targeting the 16S rRNA gene. Samples positive on either PCR were subjected to DNA sequencing and C. trachomatis PCR.

Results

The overall prevalence of Chlamydiales was 4.3% (36/847, 95% CI 3.0% to 5.8%). The prevalence of W. chondrophila was 0.6% (n = 5), C. trachomatis 1.7% (n = 14), and other Chlamydiales species 2.0% (n = 17). Infection with C. trachomatis was more common in women aged <25, of black ethnicity or with bacterial vaginosis, but this did not apply to W. chondrophila or other Chlamydiales.

Follow up was 99.9% at 16 weeks gestation and 90% at term. No infection was significantly associated with miscarriage at ≤12 weeks (prevalence 10%, 81/827) or preterm birth <37 weeks (prevalence 4%, 23/628). Of 25 samples sequenced, seven (28%) were positive for Chlamydiales bacterium sequences associated with respiratory tract infections in children.

Conclusion

In the first study to use the pan-Chlamydiales assay on female urine samples, 4% of pregnant women tested positive for Chlamydiales, including species known to be pathogenic in mothers and neonates.

Regulatory (pan-)genome of an obligate intracellular pathogen in the PVC superphylum

Like other obligate intracellular bacteria, the Chlamydiae feature a compact regulatory genome that remains uncharted owing to poor genetic tractability. Exploiting the reduced number of transcription factors (TFs) encoded in the chlamydial (pan-)genome as a model for TF control supporting the intracellular lifestyle, we determined the conserved landscape of TF specificities by ChIP-Seq (chromatin immunoprecipitation-sequencing) in the chlamydial pathogen Waddlia chondrophila. Among 10 conserved TFs, Euo emerged as a master TF targeting >100 promoters through conserved residues in a DNA excisionase-like winged helix-turn-helix-like (wHTH) fold. Minimal target (Euo) boxes were found in conserved developmentally-regulated genes governing vertical genome transmission (cytokinesis and DNA replication) and genome plasticity (transposases). Our ChIP-Seq analysis with intracellular bacteria not only reveals that global TF regulation is maintained in the reduced regulatory genomes of Chlamydiae, but also predicts that master TFs interpret genomic information in the obligate intracellular α-proteobacteria, including the rickettsiae, from which modern day mitochondria evolved.

Mouse Model of Respiratory Tract Infection Induced by Waddlia chondrophila

Waddlia chondrophila, an obligate intracellular bacterium belonging to the Chlamydiales order, is considered as an emerging pathogen. Some clinical studies highlighted a possible role of W. chondrophila in bronchiolitis, pneumonia and miscarriage. This pathogenic potential is further supported by the ability of W. chondrophila to infect and replicate within human pneumocytes, macrophages and endometrial cells. Considering that W. chondrophila might be a causative agent of respiratory tract infection, we developed a mouse model of respiratory tract infection to get insight into the pathogenesis of W. chondrophila. Following intranasal inoculation of 2 x 10⁸W. chondrophila, mice lost up to 40% of their body weight, and succumbed rapidly from infection with a death rate reaching 50% at day 4 post-inoculation. Bacterial loads, estimated by qPCR, increased from day 0 to day 3 post-infection and decreased thereafter in surviving mice. Bacterial growth was confirmed by detecting dividing bacteria using electron microscopy, and living bacteria were isolated from lungs 14 days post-infection. Immunohistochemistry and histopathology of infected lungs revealed the presence of bacteria associated with pneumonia characterized by an important multifocal inflammation. The high inflammatory score in the lungs was associated with the presence of pro-inflammatory cytokines in both serum and lungs at day 3 post-infection. This animal model supports the role of W. chondrophila as an agent of respiratory tract infection, and will help understanding the pathogenesis of this strict intracellular bacterium.

Waddlia chondrophila induces systemic infection, organ pathology, and elicits Th1-associated humoral immunity in a murine model of genital infection

Waddlia chondrophila is a known bovine abortigenic Chlamydia-related bacterium that has been associated with adverse pregnancy outcomes in human. However, there is a lack of knowledge regarding how W. chondrophila infection spreads, its ability to elicit an immune response and induce pathology. A murine model of genital infection was developed to investigate the pathogenicity and immune response associated with a W. chondrophila infection. Genital inoculation of the bacterial agent resulted in a dose-dependent infection that spread to lumbar lymph nodes and successively to spleen and liver. Bacterial-induced pathology peaked on day 14, characterized by leukocyte infiltration (uterine horn, liver, and spleen), necrosis (liver) and extramedullary hematopoiesis (spleen). Immunohistochemistry demonstrated the presence of a large number of W. chondrophila in the spleen on day 14. Robust IgG titers were detected by day 14 and remained high until day 52. IgG isotypes consisted of high IgG2a, moderate IgG3 and no detectable IgG1, indicating a Th1-associated immune response. This study provides the first evidence that W. chondrophila genital infection is capable of inducing a systemic infection that spreads to major organs, induces uterus, spleen, and liver pathology and elicits a Th1-skewed humoral response. This new animal model will help our understanding of the mechanisms related to intracellular bacteria-induced miscarriages, the most frequent complication of pregnancy that affects one in four women.

Waddlia: An emerging pathogen and a model organism to study the biology of chlamydiae

Waddlia chondrophila is an emerging pathogen associated with abortion in cattle. In humans, a growing body of evidence supports its pathogenic role in miscarriage and in respiratory tract infection. The human pathogenicity of W. chondrophila is further supported by the presence of several virulence factors including a catalase, a functional T3SS and several adhesins. Despite this medical importance, no commercial tests are available and diagnostic of this strict intracellular bacterium mainly relies on serology, PCR and immunohistochemistry. So far, the epidemiology of W. chondrophila remains largely unexplored and zoonotic, waterborne or interhuman transmission has been considered. Apart from its pathogenic role, chlamydiologists are also interested in W. chondrophila in order to better understand biological mechanisms conserved and shared with Chlamydia spp. Indeed, W. chondrophila proved to be a useful model organism to study the pathobiology of chlamydiae thanks to its rapid replication, its large size allowing precise subcellular protein localization, as well as its growth in Dictyostelium amoebae.

Permissivity of insect cells to Waddlia chondrophila, Estrella lausannensis and Parachlamydia acanthamoebae

Recent large scale studies questioning the presence of intracellular bacteria of the Chlamydiales order in ticks and fleas revealed that arthropods, similarly to mammals, reptiles, birds or fishes, can be colonized by Chlamydia-related bacteria with a predominant representation of the Rhabdochlamydiaceae and Parachlamydiaceae families. We thus investigated the permissivity of two insect cell lines towards Waddlia chondrophila, Estrella lausannensis and Parachlamydia acanthamoebae, three bacteria representative of three distinct families within the Chlamydiales order, all documented in ticks and/or in other arthropods. We demonstrated that W. chondrophila and E. lausannensis are able to very efficiently multiply in these insect cell lines. E. lausannensis however induced a rapid cytopathic effect, which somehow restricted its replication. P. acanthamoebae was not able to grow in these cell lines even if inclusions containing a few replicating bacteria could occasionally be observed.

Disassembly of a Medial Transenvelope Structure by Antibiotics during Intracellular Division

Chlamydiales possess a minimal but functional peptidoglycan precursor biosynthetic and remodeling pathway involved in the assembly of the division septum by an atypical cytokinetic machine and cryptic or modified peptidoglycan-like structure (PGLS). How this reduced cytokinetic machine collectively coordinates the invagination of the envelope has not yet been explored in Chlamydiales. In other Gram-negative bacteria, peptidoglycan provides anchor points that connect the outer membrane to the peptidoglycan during constriction using the Pal-Tol complex. Purifying PGLS and associated proteins from the chlamydial pathogen Waddlia chondrophila, we unearthed the Pal protein as a peptidoglycan-binding protein that localizes to the chlamydial division septum along with other components of the Pal-Tol complex. Together, our PGLS characterization and peptidoglycan-binding assays support the notion that diaminopimelic acid is an important determinant recruiting Pal to the division plane to coordinate the invagination of all envelope layers with the conserved Pal-Tol complex, even during osmotically protected intracellular growth.

Absence of Chlamydia-like organisms in pigs

Porcine reproductive failure, especially abortion, causes significant economic loss in the pig industry. Waddlia chondrophila and Parachlamydia acanthamoebae are potential abortigenic agents for pigs. Therefore, we investigated the presence of these two Chlamydia-like organisms in abortion-related samples originating from Belgian pig farms. All investigated samples remained negative.

In contrast to Chlamydia trachomatis, Waddlia chondrophila grows in human cells without inhibiting apoptosis, fragmenting the Golgi apparatus, or diverting post-Golgi sphingomyelin transport

The Chlamydiales are an order of obligate intracellular bacteria sharing a developmental cycle inside a cytosolic vacuole, with very diverse natural hosts, from amoebae to mammals. The clinically most important species is Chlamydia trachomatis. Many uncertainties remain as to how Chlamydia organizes its intracellular development and replication. The discovery of new Chlamydiales species from other families permits the comparative analysis of cell-biological events and may indicate events that are common to all or peculiar to some species and more or less tightly linked to "chlamydial" development. We used this approach in the infection of human cells with Waddlia chondrophila, a species from the family Waddliaceae whose natural host is uncertain. Compared to C. trachomatis, W. chondrophila had slightly different growth characteristics, including faster cytotoxicity. The embedding in cytoskeletal structures was not as pronounced as for the C. trachomatis inclusion. C. trachomatis infection generates proteolytic activity by the protease Chlamydia protease-like activity factor (CPAF), which degrades host substrates upon extraction; these substrates were not cleaved in the case of W. chondrophila. Unlike Chlamydia, W. chondrophila did not protect against staurosporine-induced apoptosis. C. trachomatis infection causes Golgi apparatus fragmentation and redirects post-Golgi sphingomyelin transport to the inclusion; both were absent from W. chondrophila-infected cells. When host cells were infected with both species, growth of both species was reduced. This study highlights differences between bacterial species that both depend on obligate intracellular replication inside an inclusion. Some features seem principally dispensable for intracellular development of Chlamydiales in vitro but may be linked to host adaptation of Chlamydia and the higher virulence of C. trachomatis.

OmpA family proteins and Pmp-like autotransporter: new adhesins of Waddlia chondrophila

Waddlia chondrophila is a obligate intracellular bacterium belonging to the Chlamydiales order, a clade that also includes the well-known classical Chlamydia responsible for a number of severe human and animal diseases. Waddlia is an emerging pathogen associated with adverse pregnancy outcomes in humans and abortion in ruminants. Adhesion to the host cell is an essential prerequisite for survival of every strict intracellular bacteria and, in classical Chlamydia, this step is partially mediated by polymorphic outer membrane proteins (Pmps), a family of highly diverse autotransporters that represent about 15% of the bacterial coding capacity. Waddlia chondrophila genome however only encodes one putative Pmp-like protein. Using a proteomic approach, we identified several bacterial proteins potentially implicated in the adhesion process and we characterized their expression during the replication cycle of the bacteria. In addition, we demonstrated that the Waddlia Pmp-like autotransporter as well as OmpA2 and OmpA3, two members of the extended Waddlia OmpA protein family, exhibit adhesive properties on epithelial cells. We hypothesize that the large diversity of the OmpA protein family is linked to the wide host range of these bacteria that are able to enter and multiply in various host cells ranging from protozoa to mammalian and fish cells.

Trafficking of Estrella lausannensis in human macrophages

Estrella lausannensis is a new member of the Chlamydiales order. Like other Chlamydia-related bacteria, it is able to replicate in amoebae and in fish cell lines. A preliminary study investigating the pathogenic potential of Chlamydia-related bacteria found a correlation between antibody response to E. lausannensis and pneumonia in children. To further investigate the pathogenic potential of E. lausannensis, we determined its ability to grow in human macrophages and its intracellular trafficking. The replication in macrophages resulted in viable E. lausannensis; however, it caused a significant cytopathic effect. The intracellular trafficking of E. lausannensis was analyzed by determining the interaction of the Estrella-containing inclusions with various endocytic markers as well as host organelles. The E. lausannensis inclusion escaped the endocytic pathway rapidly avoiding maturation into phagolysosomes by preventing both EEA-1 and LAMP-1 accumulation. Compared to Waddlia chondrophila, another Chlamydia-related bacteria, the recruitment of mitochondria and endoplasmic reticulum was minimal for E. lausannensis inclusions. Estrella lausannensis appears to use a distinct source of nutrients and energy compared to other members of the Chlamydiales order. In conclusion, we hypothesize that E. lausannensis has a restricted growth in human macrophages, due to its reduced capacity to control programmed cell death.

Role of Waddlia chondrophila placental infection in miscarriage

Waddlia chondrophila is an intracellular bacterium suspected to cause human and bovine abortion. We confirmed an association between antibodies against W. chondrophila and human miscarriage and identified this organism in placenta or genital tract of women who had had miscarriages. These results suggest a possible role of W. chondrophila infection in miscarriage.

Role of Chlamydia trachomatis and emerging Chlamydia-related bacteria in ectopic pregnancy in Vietnam

In this case-control study, we investigated the seroprevalence and molecular evidence of Chlamydia trachomatis and Waddlia chondrophila in ectopic pregnancies (EP) and uneventful control pregnancies in 343 women from Vietnam. Whereas presence of C. trachomatis IgG was strongly associated with EP [adjusted odds ratio (aOR) 5·41, 95% confidence interval (CI) 2·58-11·32], its DNA remained undetected in all tubal lesions. We confirmed an independent association between antibodies against Waddlia and previous miscarriage (aOR 1·87, 95% CI 1·02-3·42). Further investigations are needed to understand the clinical significance of Waddlia's high seroprevalence (25·9% in control pregnancies) in this urban population.

Roles of bovine Waddlia chondrophila and Chlamydia trachomatis in human preterm birth

Waddlia chondrophila and Chlamydia trachomatis are intracellular bacteria associated with human miscarriage. We investigated their role in human preterm birth. Whereas presence of Chlamydia trachomatis DNA in genital tract was associated with human preterm birth, Waddlia was not, despite being present in women's genital tracts.

Importance of amoebae as a tool to isolate amoeba-resisting microorganisms and for their ecology and evolution: the Chlamydia paradigm

Free-living amoebae are distributed worldwide and are frequently in contact with humans and animals. As cysts, they can survive in very harsh conditions and resist biocides and most disinfection procedures. Several microorganisms, called amoeba-resisting microorganisms (ARMs), have evolved to survive and multiply within these protozoa. Among them are many important pathogens, such as Legionella and Mycobacteria, and also several newly discovered Chlamydia-related bacteria, such as Parachlamydia acanthamoebae, Estrella lausannensis, Simkania negevensis or Waddlia chondrophila whose pathogenic role towards human or animal is strongly suspected. Amoebae represent an evolutionary crib for their resistant microorganisms since they can exchange genetic material with other ARMs and develop virulence traits that will be further used to infect other professional phagocytes. Moreover, amoebae constitute an ideal tool to isolate strict intracellular microorganisms from complex microbiota, since they will feed on other fast-growing bacteria, such as coliforms potentially present in the investigated samples. The paradigm that ARMs are likely resistant to macrophages, another phagocytic cell, and that they are likely virulent towards humans and animals is only partially true. Indeed, we provide examples of the Chlamydiales order that challenge this assumption and suggest that the ability to multiply in protozoa does not strictly correlate with pathogenicity and that we should rather use the ability to replicate in multiple and diverse eukaryotic cells as an indirect marker of virulence towards mammals. Thus, cell-culture-based microbial culturomics should be used in the future to try to discover new pathogenic bacterial species.

Amoebae as a tool to isolate new bacterial species, to discover new virulence factors and to study the host-pathogen interactions

Amoebae are unicellular protozoan present worldwide in several environments mainly feeding on bacteria. Some of them, the amoebae-resistant bacteria (ARBs), have evolved mechanisms to survive and replicate inside amoebal species. These mainly include legionella, mycobacteria and Chlamydia-related bacteria. Amoebae can provide a replicative niche, can act as reservoir for bacteria whereas the cystic form can protect the internalized bacteria. Moreover, the amoebae represent a Trojan horse for ARBs to infect animals. The long interaction between amoebae and bacteria has likely selected for bacterial virulence traits leading to the adaptation towards an intracellular lifestyle, and some ARBs have acquired the ability to infect mammals. This review intends to highlight the important uses of amoebae in several fields in microbiology by describing the main tools developed using amoebal cells. First, amoebae such as Acanthamoeba are used to isolate and discover new intracellular bacterial species by two main techniques: the amoebal co-culture and the amoebal enrichment. In the second part, taking Waddlia chondrophila as example, we summarize some important recent applications of amoebae to discover new bacterial virulence factors, in particular thanks to the amoebal plaque assay. Finally, the genetically tractable Dictyostelium discoideum is used as a model organism to study host-pathogen interactions, in particular with the development of several approaches to manipulate its genome that allowed the creation of a wide range of mutated strains largely shared within the Dictyostelium community.

Cell wall precursors are required to organize the chlamydial division septum

Members of the Chlamydiales order are major bacterial pathogens that divide at mid-cell, without a sequence homologue of the FtsZ cytokinetic tubulin and without a classical peptidoglycan cell wall. Moreover, the spatiotemporal mechanisms directing constriction in Chlamydia are not known. Here we show that the MreB actin homologue and its conserved regulator RodZ localize to the division furrow in Waddlia chondrophila, a member of the Chlamydiales order implicated in human miscarriage. RodZ is recruited to the septal site earlier than MreB and in a manner that depends on biosynthesis of the peptidoglycan precursor lipid II by the MurA enzyme. By contrast, crosslinking of lipid II peptides by the Pbp3 transpeptidase disperses RodZ from the septum. Altogether, these findings provide a cytological framework for understanding chlamydial cytokinesis driven by septal cell wall synthesis.

Laboratory diagnosis of ruminant abortion in Europe

Abortion in ruminants is a major cause of economic loss worldwide, and the management and control of outbreaks is important in limiting their spread, and in preventing zoonotic infections. Given that rapid and accurate laboratory diagnosis is central to controlling abortion outbreaks, the submission of tissue samples to laboratories offering the most appropriate tests is essential. Direct antigen and/or DNA detection methods are the currently preferred methods of reaching an aetiological diagnosis, and ideally these results are confirmed by the demonstration of corresponding macroscopic and/or histopathological lesions in the fetus and/or the placenta. However, the costs of laboratory examinations may be considerable and, even under optimal conditions, the percentage of aetiological diagnoses reached can be relatively low. This review focuses on the most commonly occurring and important abortifacient pathogens of ruminant species in Europe highlighting their epizootic and zoonotic potential. The performance characteristics of the various diagnostic methods used, including their specific advantages and limitations, are discussed.