Parachlamydiaceae: potential emerging pathogens

Parachlamydia acanthamoebae: disease-causing pathogen or opportunistic bystander?

Introduction. Parachlamydia acanthamoebae is an obligate intracellular bacterium related to disease-causing bacteria like Chlamydia trachomatis and Chlamydia pneumoniae and is thus classified within the Chlamydiales order. Parachlamydia was initially discovered within an Acanthamoeba strain isolated from water in a humidifier during an investigation of an outbreak of respiratory infections in humans.Gap Statement. The disease-causing potential of this bacterium is not fully understood, but Parachlamydia has been associated with bronchiolitis, bronchitis, aspiration pneumonia and community-acquired pneumonia in humans. Additionally, diagnostic testing for Parachlamydia infection is not routinely performed, indicating that prevalence is underreported.Aim. This JMM profile aims to gauge what is currently known about the pathogenic potential of P. acanthamoebae and bring awareness to gaps in knowledge.Results. Amoebae appear to be the main reservoir of P. acanthamoebae and likely enter the nasal passages through contaminated water sources or contact with contaminated animals. The infected amoebae may then descend to the lower respiratory tract where the lytic cycle is triggered, causing human infection.Conclusion. By implementing serology and molecular testing, as well as conducting additional epidemiological studies, a better understanding of the association of human colonization with disease outcomes can be achieved.

Polystyrene nanoplastics sequester the toxicity mitigating potential of probiotics by altering gut microbiota in grass carp (Ctenopharyngodon idella)

This study evaluated the role of probiotics in enhancing intestinal immunity and mitigating polystyrene nanoplastics (PS-NPs)-induced toxicity in grass carp (Ctenopharyngodon idella). Grass carp were fed probiotics (Bacillus subtilis, Bacillus velezensis, Lactobacillus reuteri, and Lactococcus lactis) for two weeks before being exposed to PS-NPs for five days. Probiotic pretreatment alleviated PS-NPs-induced intestinal damage, with Bacillus velezensis and Lactococcus lactis groups showing milder vacuolation and villus breakage than other groups. Probiotic-treated fish exhibited transient increases in antioxidant enzyme activities (CAT, SOD, MPO) and immune gene expression (IL-6, IL-8, IL-10, IL-1β, TNF-α, and IFN-γ2) shortly after exposure, followed by significant downregulation over time. Higher abundance of the gut dominant phylum Proteobacteria was observed in four probiotic groups exposed to PS-NPs than that in the blank control group. The Clostridium phylum showed a significant decrease in the abundance both in the LRS-PS100 and LLS-PS100 groups, while the abundance of the Thick-walled phylum increased. The Spearman correlation matrix revealed that specific gut microbiota, such as Serratia, Neisseria, and Lactococcus, were significantly associated with enzymatic activities and immune system related genes' expressions. Probiotic pretreatment enhanced the intestinal immune response of grass carp. However, this enhanced immune response was insufficient to counteract the toxic effects of PS-NPs exposure, particularly in terms of oxidative stress levels and gut microbial diversity. This study offers new insights into the potential of probiotics to combat NPs pollution in aquaculture. It emphasizes the need for further research to explore various probiotic combinations. Future studies should also investigate optimal dosages and durations to effectively mitigate the biological toxicity of NPs pollution.

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.

The inside scoop: Comparative genomics of two intranuclear bacteria, "Candidatus Berkiella cookevillensis" and "Candidatus Berkiella aquae"

"Candidatus Berkiella cookevillensis" (strain CC99) and "Candidatus Berkiella aquae" (strain HT99), belonging to the Coxiellaceae family, are gram-negative bacteria isolated from amoebae in biofilms present in human-constructed water systems. Both bacteria are obligately intracellular, requiring host cells for growth and replication. The intracellular bacteria-containing vacuoles of both bacteria closely associate with or enter the nuclei of their host cells. In this study, we analyzed the genome sequences of CC99 and HT99 to better understand their biology and intracellular lifestyles. The CC99 genome has a size of 2.9Mb (37.9% GC) and contains 2,651 protein-encoding genes (PEGs) while the HT99 genome has a size of 3.6Mb (39.4% GC) and contains 3,238 PEGs. Both bacteria encode high proportions of hypothetical proteins (CC99: 46.5%; HT99: 51.3%). The central metabolic pathways of both bacteria appear largely intact. Genes for enzymes involved in the glycolytic pathway, the non-oxidative branch of the phosphate pathway, the tricarboxylic acid pathway, and the respiratory chain were present. Both bacteria, however, are missing genes for the synthesis of several amino acids, suggesting reliance on their host for amino acids and intermediates. Genes for type I and type IV (dot/icm) secretion systems as well as type IV pili were identified in both bacteria. Moreover, both bacteria contain genes encoding large numbers of putative effector proteins, including several with eukaryotic-like domains such as, ankyrin repeats, tetratricopeptide repeats, and leucine-rich repeats, characteristic of other intracellular bacteria.

Identification of Parachlamydiaceae DNA in nasal and rectal passages of healthy dairy cattle

AIMS

The order Chlamydiales comprises a broad range of bacterial pathogens and endosymbionts, which infect a wide variety of host species. Within this order, members of the family Parachlamydiaceae, which includes Parachlamydia and Neochlamydia species, have been particularly associated with infections in both humans and cattle, including having a potential pathogenic role in cases of bovine abortion. While the route of transmission has yet to be defined, it has been hypothesised that asymptomatic carriage and contamination of the immediate environment may be a route of inter-animal transmission. We investigated the asymptomatic carriage of Chlamydia-related organisms in healthy cattle.

METHODS & RESULTS

DNA was isolated from nasal and rectal swabs obtained from 38 healthy dairy heifers. A Chlamydiales sp. 16S rRNA qPCR was performed on each sample. A total of 18/38 nasal samples and all 38/38 rectal samples were identified as positive for Chlamydiales sp. Each positive sample was sequenced confirming the presence of DNA belonging to the Parachlamydiaceae.

CONCLUSIONS

The presence of Parachlamydiaceae DNA in nasal and rectal swab samples of healthy cattle provides evidence for the asymptomatic carriage of parachlamydial organisms within cattle.

SIGNIFICANCE & IMPACT OF THE STUDY

The study provides evidence of potential routes of environmental contamination that could provide a route for inter-animal and animal transmission of Parachlamydiaceae.

Characterization of eukaryotic microbiome and associated bacteria communities in a drinking water treatment plant

The effectiveness of drinking water treatment is critical to achieve an optimal and safe drinking water. Disinfection is one of the most important steps to eliminate the health concern caused by the microbial population in this type of water. However, no study has evaluated the changes in its microbiome, specially the eukaryotic microbiome, and the fates of opportunistic pathogens generated by UV disinfection with medium-pressure mercury lamps in drinking water treatment plants (DWTPs). In this work, the eukaryotic community composition of a DWTP with UV disinfection was evaluated before and after a UV disinfection treatment by means of Illumina 18S rRNA amplicon-based sequencing. Among the physicochemical parameters analysed, flow and nitrate appeared to be related with the changes in the eukaryotic microbiome shape. Public health concern eukaryotic organisms such as Blastocystis, Entamoeba, Acanthamoeba, Hartmannella, Naegleria, Microsporidium or Caenorhabditis were identified. Additionally, the relation between the occurrence of some human bacterial pathogens and the presence of some eukaryotic organisms has been studied. The presence of some human bacterial pathogens such as Arcobacter, Mycobacterium, Pseudomonas and Parachlamydia were statistically correlated with the presence of some eukaryotic carriers showing the public health risk due to the bacterial pathogens they could shelter.

Several New Putative Bacterial ADP-Ribosyltransferase Toxins Are Revealed from In Silico Data Mining, Including the Novel Toxin Vorin, Encoded by the Fire Blight Pathogen Erwinia amylovora

Mono-ADP-ribosyltransferase (mART) toxins are secreted by several pathogenic bacteria that disrupt vital host cell processes in deadly diseases like cholera and whooping cough. In the last two decades, the discovery of mART toxins has helped uncover the mechanisms of disease employed by pathogens impacting agriculture, aquaculture, and human health. Due to the current abundance of mARTs in bacterial genomes, and an unprecedented availability of genomic sequence data, mART toxins are amenable to discovery using an in silico strategy involving a series of sequence pattern filters and structural predictions. In this work, a bioinformatics approach was used to discover six bacterial mART sequences, one of which was a functional mART toxin encoded by the plant pathogen, Erwinia amylovora, called Vorin. Using a yeast growth-deficiency assay, we show that wild-type Vorin inhibited yeast cell growth, while catalytic variants reversed the growth-defective phenotype. Quantitative mass spectrometry analysis revealed that Vorin may cause eukaryotic host cell death by suppressing the initiation of autophagic processes. The genomic neighbourhood of Vorin indicated that it is a Type-VI-secreted effector, and co-expression experiments showed that Vorin is neutralized by binding of a cognate immunity protein, VorinI. We demonstrate that Vorin may also act as an antibacterial effector, since bacterial expression of Vorin was not achieved in the absence of VorinI. Vorin is the newest member of the mART family; further characterization of the Vorin/VorinI complex may help refine inhibitor design for mART toxins from other deadly pathogens.

Biphasic Metabolism and Host Interaction of a Chlamydial Symbiont

Chlamydiae are obligate intracellular bacteria comprising well-known human pathogens and ubiquitous symbionts of protists, which are characterized by a unique developmental cycle. Here we comprehensively analyzed gene expression dynamics of Protochlamydia amoebophila during infection of its Acanthamoeba host by RNA sequencing. This revealed a highly dynamic transcriptional landscape, where major transcriptional shifts are conserved among chlamydial symbionts and pathogens. Our data served to propose a time-resolved model for type III protein secretion during the developmental cycle, and we provide evidence for a biphasic metabolism of P. amoebophila during infection, which involves energy parasitism and amino acids as the carbon source during initial stages and a postreplicative switch to endogenous glucose-based ATP production. This fits well with major transcriptional changes in the amoeba host, where upregulation of complex sugar breakdown precedes the P. amoebophila metabolic switch. The biphasic chlamydial metabolism represents a unique adaptation to exploit eukaryotic host cells, which likely contributed to the evolutionary success of this group of microbes. IMPORTANCE Chlamydiae are known as major bacterial pathogens of humans, causing the ancient disease trachoma, but they are also frequently found in the environment where they infect ubiquitous protists such as amoebae. All known chlamydiae require a eukaryotic host cell to thrive. Using the environmental chlamydia Protochlamydia amoebophila within its natural host, Acanthamoeba castellanii, we investigated gene expression dynamics in vivo and throughout the complete chlamydial developmental cycle for the first time. This allowed us to infer how a major virulence mechanism, the type III secretion system, is regulated and employed, and we show that the physiology of chlamydiae undergoes a complete shift regarding carbon metabolism and energy generation. This study provides comprehensive insights into the infection strategy of chlamydiae and reveals a unique adaptation to life within a eukaryotic host cell.

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.

Detection of Mycobacteria and Chlamydiae in Granulomatous Inflammation of Reptiles: A Retrospective Study

A retrospective study on reptile tissues presenting with granulomatous inflammation was performed to detect the possible presence of mycobacteria and chlamydiae in these lesions. Ninety cases including 48 snakes, 27 chelonians, and 15 lizards were selected. Mycobacteria were detected by Ziehl-Neelsen (ZN) staining and a broad-range polymerase chain reaction (PCR) followed by DNA sequencing. To detect chlamydiae, immunohistochemistry with monoclonal antibodies against chlamydial lipopolysaccharide (LPS) and a Chlamydiales order-specific PCR and sequencing were applied. Acid-fast bacilli were found in 14 cases (15.6%) by ZN staining and in 23 cases (25.6%) by PCR. Sequence analysis revealed the presence of Mycobacteria other than Mycobacterium tuberculosis complex (MOTT). Chlamydial LPS antigen was observed within granulomas from five samples (5.6%), whereas the PCR screen revealed 58 positive cases (64.4%). Of these, 9 cases (10%) showed 98–99% similarity to Chlamydophila ( Cp.) pneumoniae and 49 cases (54.4%) displayed a high similarity (88–97%) to the newly described “Chlamydia-like” microorganisms Parachlamydia acanthamoebae and Simkania negevensis. Results from this study confirm, on the one hand, that MOTT are probably the most important infectious etiology for granulomatous inflammation in reptiles. On the other hand, they indicate that chlamydia infects reptiles and that Cp. pneumoniae should be considered an etiological agent of granulomatous lesions of reptiles. Because both MOTT and Cp. pneumoniae are human pathogens, the potential of zoonotic transmission from reptiles to humans has to be considered. In contrast, the significance of Chlamydia-like isolates remains completely open, and further studies are needed to evaluate their role.

Impact of genomics on the understanding of microbial evolution and classification: the importance of Darwin's views on classification

Analyses of genome sequences, by some approaches, suggest that the widespread occurrence of horizontal gene transfers (HGTs) in prokaryotes disguises their evolutionary relationships and have led to questioning of the Darwinian model of evolution for prokaryotes. These inferences are critically examined in the light of comparative genome analysis, characteristic synapomorphies, phylogenetic trees and Darwin's views on examining evolutionary relationships. Genome sequences are enabling discovery of numerous molecular markers (synapomorphies) such as conserved signature indels (CSIs) and conserved signature proteins (CSPs), which are distinctive characteristics of different prokaryotic taxa. Based on these molecular markers, exhibiting high degree of specificity and predictive ability, numerous prokaryotic taxa of different ranks, currently identified based on the 16S rRNA gene trees, can now be reliably demarcated in molecular terms. Within all studied groups, multiple CSIs and CSPs have been identified for successive nested clades providing reliable information regarding their hierarchical relationships and these inferences are not affected by HGTs. These results strongly support Darwin's views on evolution and classification and supplement the current phylogenetic framework based on 16S rRNA in important respects. The identified molecular markers provide important means for developing novel diagnostics, therapeutics and for functional studies providing important insights regarding prokaryotic taxa.

Effect of Parachlamydia acanthamoebae on pulmonary function parameters in a bovine respiratory model

The aim of this study was to evaluate pulmonary dysfunction induced by experimental infection with Parachlamydia acanthamoebae in calves. Intrabronchial inoculation with P. acanthamoebae was performed in 31 calves aged 2-3 months old at two different challenge doses of 10(8) and 10(10) inclusion-forming units (IFU) per animal. Control animals received heat inactivated bacteria. The effects on pulmonary gas exchange were determined by arterial blood gas analysis and haemoximetry during the 7 days post inoculation (DPI). For pulmonary function testing (PFT), impulse oscillometry, capnography, and measurement of O2 uptake were undertaken in spontaneously breathing animals 7 and 3 days before inoculation and were repeated until 10 DPI. In the early phase after challenge (1-3 DPI), mild hypoxaemia occurred, which was accompanied by a significant reduction in both tidal and alveolar volumes (each related to bodyweight, BW). In parallel, expiratory flow rate and specific ventilation (i.e. minute ventilation related to O2 uptake) were significantly increased. Minute and alveolar ventilations (each related to metabolic BW) increased significantly due to higher respiratory rates, lasting until 4 and 5 DPI, respectively. Oxygen uptake was slightly reduced during the first 2 days after challenge, but increased significantly during the recovery phase, from 4 to 8 DPI. No deterioration in respiratory mechanics or acid-base balance was observed. Respiratory infection with 10(10) IFU P. acanthamoebae per calf induced mild respiratory dysfunction, mainly characterised by hypoxaemia. The study's findings do not indicate severe pathophysiological consequences of P. acanthamoebae infection on pulmonary function in the bovine host.

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.

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.

The high prevalence and diversity of Chlamydiales DNA within Ixodes ricinus ticks suggest a role for ticks as reservoirs and vectors of Chlamydia-related bacteria

The Chlamydiales order is composed of nine families of strictly intracellular bacteria. Among them, Chlamydia trachomatis, C. pneumoniae, and C. psittaci are established human pathogens, whereas Waddlia chondrophila and Parachlamydia acanthamoebae have emerged as new pathogens in humans. However, despite their medical importance, their biodiversity and ecology remain to be studied. Even if arthropods and, particularly, ticks are well known to be vectors of numerous infectious agents such as viruses and bacteria, virtually nothing is known about ticks and chlamydia. This study investigated the prevalence of Chlamydiae in ticks. Specifically, 62,889 Ixodes ricinus ticks, consolidated into 8,534 pools, were sampled in 172 collection sites throughout Switzerland and were investigated using pan-Chlamydiales quantitative PCR (qPCR) for the presence of Chlamydiales DNA. Among the pools, 543 (6.4%) gave positive results and the estimated prevalence in individual ticks was 0.89%. Among those pools with positive results, we obtained 16S rRNA sequences for 359 samples, allowing classification of Chlamydiales DNA at the family level. A high level of biodiversity was observed, since six of the nine families belonging to the Chlamydiales order were detected. Those most common were Parachlamydiaceae (33.1%) and Rhabdochlamydiaceae (29.2%). "Unclassified Chlamydiales" (31.8%) were also often detected. Thanks to the huge amount of Chlamydiales DNA recovered from ticks, this report opens up new perspectives on further work focusing on whole-genome sequencing to increase our knowledge about Chlamydiales biodiversity. This report of an epidemiological study also demonstrates the presence of Chlamydia-related bacteria within Ixodes ricinus ticks and suggests a role for ticks in the transmission of and as a reservoir for these emerging pathogenic Chlamydia-related bacteria.

A bovine model of a respiratory Parachlamydia acanthamoebae infection

The aim of this study was to evaluate the pathogenicity of Parachlamydia (P.) acanthamoebae as a potential agent of lower respiratory tract disease in a bovine model of induced lung infection. Intrabronchial inoculation with P. acanthamoebae was performed in healthy calves aged 2-3 months using two challenge doses: 10(8) and 10(10) bacteria per animal. Controls received 10(8) heat-inactivated bacteria. Challenge with 10(8) viable Parachlamydia resulted in a mild degree of general indisposition, whereas 10(10) bacteria induced a more severe respiratory illness becoming apparent 1-2 days post inoculation (dpi), affecting 9/9 (100%) animals and lasting for 6 days. The extent of macroscopic pulmonary lesions was as high as 6.6 (6.0)% [median (range)] of lung tissue at 2-4 dpi and correlated with parachlamydial genomic copy numbers detected by PCR, and with bacterial load estimated by immunohistochemistry in lung tissue. Clinical outcome, acute phase reactants, pathological findings and bacterial load exhibited an initial dose-dependent effect on severity. Animals fully recovered from clinical signs of respiratory disease within 5 days. The bovine lung was shown to be moderately susceptible to P. acanthamoebae, exhibiting a transient pneumonic inflammation after intrabronchial challenge. Further studies are warranted to determine the precise pathophysiologic pathways of host-pathogen interaction.

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.

Presence of Chlamydiales DNA in ticks and fleas suggests that ticks are carriers of Chlamydiae

The Chlamydiales order includes the Chlamydiaceae, Parachlamydiaceae, Waddliaceae, Simkaniaceae, Criblamydiaceae, Rhabdochlamydiaceae, Clavichlamydiaceae, and Piscichlamydiaceae families. Members of the Chlamydiales order are obligate intracellular bacteria that replicate within eukaryotic cells of different origins including humans, animals, and amoebae. Many of these bacteria are pathogens or emerging pathogens of both humans and animals, but their true diversity is largely underestimated, and their ecology remains to be investigated. Considering their potential threat on human health, it is important to expand our knowledge on the diversity of Chlamydiae, but also to define the host range colonized by these bacteria. Thus, using a new pan-Chlamydiales PCR, we analyzed the prevalence of Chlamydiales DNA in ticks and fleas, which are important vectors of several viral and bacterial infectious diseases. To conduct this study, 1340 Ixodes ricinus ticks prepared in 192 pools were collected in Switzerland and 55 other ticks belonging to different tick species and 97 fleas belonging to different flea species were harvested in Algeria. In Switzerland, the prevalence of Chlamydiales DNA in the 192 pools was equal to 28.1% (54/192) which represents an estimated prevalence in the 1340 individual ticks of between 4.0% and 28.4%. The pan-Chlamydiales qPCR was positive for 45% (25/55) of tick samples collected in Algeria. The sequencing of the positive qPCR amplicons revealed a high diversity of Chlamydiales species. Most of them belonged to the Rhabdochlamydiaceae and Parachlamydiaceae families. Thus, ticks may carry Chlamydiales and should thus be considered as possible vectors for Chlamydiales propagation to both humans and animals.

Chlamydia exploit the mammalian tryptophan-depletion defense strategy as a counter-defensive cue to trigger a survival state of persistence

We previously proposed that in Chlamydiaceae rapid vegetative growth and a quiescent state of survival (persistence) depend upon alternative protein translational profiles dictated by host tryptophan (Trp) availability. These alternative profiles correspond, respectively, with a set of chlamydial proteins having higher-than-predicted contents of Trp ("Up-Trp" selection), or with another set exhibiting lower-than-predicted contents of Trp ("Down-Trp" selection). A comparative evaluation of Chlamydiaceae proteomes for Trp content has now been extended to a number of other taxon families within the Chlamydiales Order. At the Order level, elevated Trp content occurs for transporters of nucleotides, S-adenosylmethionine (SAM), dicarboxylate substrates, and Trp itself. For Trp and nucleotide transporters, this is even more pronounced in other chlamydiae families (Parachlamydiaceae, Waddliaceae, and Simkaniaceae) due to extensive paralog expansion. This suggests that intracellular Trp availability served as an ancient survival cue for enhancement or restraint of chlamydial metabolism in the common Chlamydiales ancestor. The Chlamydiaceae Family further strengthened Up-Trp selection for proteins that function in cell division, lipopolysaccharide biosynthesis, and methyltransferase reactions. Some proteins that exhibit Up-Trp selection are uniquely present in the Chlamydiaceae, e.g., cytotoxin and the paralog families of polymorphic membrane proteins (Pmp's). A striking instance of Down-Trp selection in the Chlamydiaceae is the chorismate biosynthesis pathway and the connecting menaquinone pathway. The newly recognized 1,4-dihydroxy-6-napthoate pathway of menaquinone biosynthesis operates in Chlamydiaceae, whereas the classic 2-napthoate pathway is used in the other Chlamydiales families. Because of the extreme Down-Trp selection, it would appear that menaquinone biosynthesis is particularly important to the integrity of the persistent state maintained under conditions of severe Trp limitation, and may thus be critical for perpetuation of chronic disease states.

Isolation and molecular characterization of potentially pathogenic Acanthamoeba genotypes from diverse water resources including household drinking water from Khyber Pakhtunkhwa, Pakistan

Acanthamoeba, an opportunistic protozoan pathogen, is ubiquitous in nature, and therefore plays a predatory role and helps control microbial communities in the ecosystem. These Acanthamoeba species are recognized as opportunistic human pathogens that may cause blinding keratitis and rare but fatal granulomatous encephalitis. To date, there is not a single report demonstrating Acanthamoeba isolation and identification from environmental sources in Pakistan, and that is the aim of this study. Acanthamoeba were identified by morphological characteristics of their cysts on non-nutrient agar plates seeded with Escherichia coli. Additionally, the polymerase chain reaction (PCR) was performed with genus-specific primers followed by direct sequencing of the PCR product for molecular identification. Furthermore, our PCR and sequencing results confirmed seven different pathogenic and nonpathogenic genotypes, including T2-T10, T4, T5, T7, T15, T16, and T17. To the best of our knowledge, we have identified and isolated Acanthamoeba sp., for the first time, from water resources of Khyber Pakhtunkhwa, Pakistan. There is an urgent need to address (1) the pathogenic potential of the identified genotypes and (2) explore other environmental sources from the country to examine the water quality and the current status of Acanthamoeba species in Pakistan, which may be a potential threat for public health across the country.

Serologic prevalence of amoeba-associated microorganisms in intensive care unit pneumonia patients

BACKGROUND

Patients admitted to intensive care units are frequently exposed to pathogenic microorganisms present in their environment. Exposure to these microbes may lead to the development of hospital-acquired infections that complicate the illness and may be fatal. Amoeba-associated microorganisms (AAMs) are frequently isolated from hospital water networks and are reported to be associated to cases of community and hospital-acquired pneumonia.

METHODOLOGY/PRINCIPAL FINDINGS

We used a multiplexed immunofluorescence assay to test for the presence of antibodies against AAMs in sera of intensive care unit (ICU) pneumonia patients and compared to patients at the admission to the ICU (controls). Our results show that some AAMs may be more frequently detected in patients who had hospital-acquired pneumonia than in controls, whereas other AAMs are ubiquitously detected. However, ICU patients seem to exhibit increasing immune response to AAMs when the ICU stay is prolonged. Moreover, concomitant antibodies responses against seven different microorganisms (5 Rhizobiales, Balneatrix alpica, and Mimivirus) were observed in the serum of patients that had a prolonged ICU stay.

CONCLUSIONS/SIGNIFICANCE

Our work partially confirms the results of previous studies, which show that ICU patients would be exposed to water amoeba-associated microorganisms, and provides information about the magnitude of AAM infection in ICU patients, especially patients that have a prolonged ICU stay. However, the incidence of this exposure on the development of pneumonia remains to assess.

High abundance of novel environmental chlamydiae in a Tyrrhenian coastal lake (Lago di Paola, Italy)

For a long time the bacterial phylum of Chlamydiae exclusively consisted of one family of obligate intracellular bacteria, the Chlamydiaceae, which encompassed causative agents of severe diseases. In the 1990s, environmental chlamydiae were discovered as symbionts of free-living amoebae and other eukaryotic hosts. During a sampling campaign in September 2008, while monitoring Planctomycetes, we retrieved 20 almost full-length 16S rRNA gene sequences affiliated with Chlamydiales from a lake at the Tyrrhenian coast of central Italy (Lago di Paola, Latium). Two main clusters were identified. The nine sequences within the tight cluster I shared ∼98% identity, just like the six sequences of cluster II. The 16S rRNA sequence identity between the two novel groups was with 88% higher than with all known families of the order Chlamydiales. Four types of less frequent chlamydial 16S rRNA sequences were also detected. Two oligonucleotide probes were designed, and optimized. Chl282 targets the cluster I and almost all other Chlamydiales, while Chl282bis targets the cluster II and few other sequences. By catalysed reporter deposition fluorescence in situ hybridization (CARD-FISH), we identified in the Lago di Paola picoplankton abundant tiny cells with dot-shaped morphology and, interestingly, rarely also protists with intracellular pleomorphic chlamydiae. Abundances of the novel chlamydial clusters were up to 5 × 10(4) cells per millilitre. The two clusters were also detected in similar numbers during a second sampling in October 2010. This confirmed the relevance of the two newly described clusters of chlamydiae in Lago di Paola, not only enlarging the knowledge on the biodiversity of environmental chlamydiae in aquatic habitats, but also raising sanitary issues that should be addressed in the future.

Insight into cross-talk between intra-amoebal pathogens

Background

Amoebae are phagocytic protists where genetic exchanges might take place between amoeba-resistant bacteria. These amoebal pathogens are able to escape the phagocytic behaviour of their host. They belong to different bacterial phyla and often show a larger genome size than human-infecting pathogens. This characteristic is proposed to be the result of frequent gene exchanges with other bacteria that share a sympatric lifestyle and contrasts with the genome reduction observed among strict human pathogens.

Results

We sequenced the genome of a new amoebal pathogen, Legionella drancourtii, and compared its gene content to that of a Chlamydia-related bacterium, Parachlamydia acanthamoebae. Phylogenetic reconstructions identified seven potential horizontal gene transfers (HGTs) between the two amoeba-resistant bacteria, including a complete operon of four genes that encodes an ABC-type transporter. These comparisons pinpointed potential cases of gene exchange between P. acanthamoebae and Legionella pneumophila, as well as gene exchanges between other members of the Legionellales and Chlamydiales orders. Moreover, nine cases represent possible HGTs between representatives from the Legionellales or Chlamydiales and members of the Rickettsiales order.

Conclusions

This study identifies numerous gene exchanges between intracellular Legionellales and Chlamydiales bacteria, which could preferentially occur within common inclusions in their amoebal hosts. Therefore it contributes to improve our knowledge on the intra-amoebal gene properties associated to their specific lifestyle.

Permissivity of fish cell lines to three Chlamydia-related bacteria: Waddlia chondrophila, Estrella lausannensis and Parachlamydia acanthamoebae

Epitheliocystis is an infectious disease affecting gills and skin of various freshwater and marine fishes, associated with high mortality and reduced growth of survivors. Candidatus Piscichlamydia salmonis and Clavochlamydia salmonicola have recently been identified as aetiological agents of epitheliocystis in Atlantic Salmon. In addition, several other members of the Chlamydiales order have been identified in other fish species. To clarify the pathogenicity of Chlamydia-like organisms towards fishes, we investigated the permissivity of two fish cell lines, EPC-175 (Fathead Minnow) and RTG-2 (rainbow trout) to three Chlamydia-related bacteria: Waddlia chondrophila, Parachlamydia acanthamoebae and Estrella lausannensis. Quantitative PCR and immunofluorescence demonstrated that W. chondrophila and, to a lesser extent, E. lausannensis were able to replicate in the two cell lines tested. Waddlia chondrophila multiplied rapidly in its host cell and a strong cytopathic effect was observed. During E. lausannensis infection, we observed a limited replication of the bacteria not followed by host cell lysis. Very limited replication of P. acanthamoebae was observed in both cell lines tested. Given its high infectivity and cytopathic effect towards fish cell lines, W. chondrophila represents the most interesting Chlamydia-related bacteria to be used to develop an in vivo model of epitheliocystis disease in fishes.

Molecular detection of Chlamydia-like organisms in cattle drinking water

A substantial proportion of the causes of infectious bovine abortion remain largely undiagnosed, potentially due to the presence of previously unrecognised infectious agents. Recently, several reports have demonstrated the presence of Parachlamydia sp. in placental and foetal tissues derived from bovine abortions of unknown aetiology but the route of transmission remains undefined. The drinking water from one such recent case study was analysed for the presence of Parachlamydia sp. as a potential source of infection. Chlamydiales sp. 16S rRNA genes were PCR-amplified from the drinking water and a 16S rRNA gene clone library constructed. DNA sequencing of thirty-one clones indicated the presence of organisms belonging to the Parachlamydiaceae, specifically the genera Parachlamydia and Neochlamydia. Seven 16S rRNA gene sequences were identical to a Parachlamydia sp. sequence obtained from placental tissue from an abortion case originating from the same farm. These results raise the possibility that the drinking water is a source of Parachlamydia, which may play a role in infectious bovine abortion.

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

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.

Role of MyD88 and Toll-like receptors 2 and 4 in the sensing of Parachlamydia acanthamoebae

Parachlamydia acanthamoebae is a Chlamydia-related organism whose pathogenic role in pneumonia is supported by serological and molecular clinical studies and an experimental mouse model of lung infection. Toll-like receptors (TLRs) play a seminal role in sensing microbial products and initiating innate immune responses. The aim of this study was to investigate the roles of MyD88, TLR2, and TLR4 in the interaction of Parachlamydia with macrophages. Here, we showed that Parachlamydia entered bone-marrow derived macrophages (BMDMs) in a TLR-independent manner but did not multiply intracellularly. Interestingly, compared to live bacteria, heat-inactivated Parachlamydia induced the production of substantial amounts of tumor necrosis factor alpha (TNF), interleukin-6 (IL-6), and IL-12p40 by BMDMs and of TNF and IL-6 by peritoneal macrophages as well as RAW 264.7 and J774 macrophage cell lines. Cytokine production by BMDMs, which was partially inhibited upon trypsin treatment of Parachlamydia, was dependent on MyD88, TLR4, and, to a lesser extent, TLR2. Finally, MyD88(-/-), TLR4(-/-), and TLR2(-/-) mice were as resistant as wild-type mice to lung infection following the intratracheal instillation of Parachlamydia. Thus, in contrast to Chlamydia pneumoniae, Parachlamydia acanthamoebae weakly stimulates macrophages, potentially compensating for its low replication capacity in macrophages by escaping the innate immune surveillance.

Proteomic aspects of Parachlamydia acanthamoebae infection in Acanthamoeba spp

The free-living but facultatively pathogenic amoebae of the genus Acanthamoeba are frequently infected with bacterial endosymbionts that can have a profound influence on the physiology and viability of their host. Parachlamydia acanthamoebae, a chlamydial endosymbiont in acanthamoebae, is known to be either symbiotic or lytic to its host, depending on the ambient conditions, for example, temperature. Moreover, parachlamydiae can also inhibit the encystment process in Acanthamoeba, an essential survival strategy of their host for the evasion of chemotherapeutic agents, heat, desiccation and radiation. To obtain a more detailed picture of the intracellular interactions of parachlamydiae and acanthamoebae, we studied parachlamydial infection in several Acanthamoeba isolates at the proteomic level by means of two-dimensional gel electrophoresis (2DE) and mass spectrometry. We observed that P. acanthamoebae can infect all three morphological subtypes of the genus Acanthamoeba and that the proteome pattern of released P. acanthamoebae elementary bodies was always practically identical regardless of the Acanthamoeba strain infected. Moreover, by comparing proteome patterns of encysting cells from infected and uninfected Acanthamoeba cultures, it was shown that encystment is blocked by P. acanthamoebae at a very early stage. Finally, on 2D-gels of purified P. acanthamoebae from culture supernatants, a subunit of the NADH-ubiquinone oxidoreductase complex, that is, an enzyme that has been described as an indicator for bacterial virulence was identified by a mass spectrometric and bioinformatic approach.

Raman microspectroscopy reveals long-term extracellular activity of Chlamydiae

The phylum Chlamydiae consists exclusively of obligate intracellular bacteria. Some of them are formidable pathogens of humans, while others occur as symbionts of amoebae. These genetically intractable bacteria possess a developmental cycle consisting of replicative reticulate bodies and infectious elementary bodies, which are believed to be physiologically inactive. Confocal Raman microspectroscopy was applied to differentiate between reticulate bodies and elementary bodies of Protochlamydia amoebophila and to demonstrate in situ the labelling of this amoeba symbiont after addition of isotope-labelled phenylalanine. Unexpectedly, uptake of this amino acid was also observed for both developmental stages for up to 3 weeks, if incubated extracellularly with labelled phenylalanine, and P. amoebophila remained infective during this period. Furthermore, P. amoebophila energizes its membrane and performs protein synthesis outside of its host. Importantly, amino acid uptake and protein synthesis after extended extracellular incubation could also be demonstrated for the human pathogen Chlamydia trachomatis, which synthesizes stress-related proteins under these conditions as shown by 2-D gel electrophoresis and MALDI-TOF/TOF mass spectrometry. These findings change our perception of chlamydial biology and reveal that host-free analyses possess a previously not recognized potential for direct experimental access to these elusive microorganisms.

Free-living amoebae: Biological by-passes in water treatment

Free-living amoebae constitute reservoirs for many bacteria including not only well-known pathogens but also emerging pathogens responsible for respiratory diseases, and contribute to the protection, survival and dissemination of these bacteria in water systems, despite the application of disinfection or thermal treatments. In this article we review the available information on the presence of free-living amoebae and amoebae-resisting bacteria in drinking water systems, on the factors that contribute to their presence in the water and/or the biofilms, on the possible control measures and their effectiveness, and we identify some gaps in current knowledge needing further research.

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

Waddlia chondrophila is considered as an emerging human pathogen likely involved in miscarriage and lower respiratory tract infections. Given the low sensitivity of cell culture to recover such an obligate intracellular bacteria, molecular-based diagnostic approaches are warranted. We thus developed a real-time PCR that amplifies Waddlia chondrophila DNA. Specific primers and probe were selected to target the 16S rRNA gene. The PCR specifically amplified W. chondrophila but did not amplify other related-bacteria such as Parachlamydia acanthamoebae, Simkania negevensis and Chlamydia pneumoniae. The PCR exhibited a good intra-run and inter-run reproducibility and a sensitivity of less than ten copies of the positive control. This real-time PCR was then applied to 32 nasopharyngeal aspirates taken from children with bronchiolitis not due to respiratory syncytial virus (RSV). Three samples revealed to be Waddlia positive, suggesting a possible role of this Chlamydia-related bacteria in this setting.

Parachlamydia acanthamoebae, an emerging agent of pneumonia

Parachlamydia acanthamoebae is a Chlamydia-like organism that easily grows within Acanthamoeba spp. Thus, it probably uses these widespread free-living amoebae as a replicative niche, a cosmopolite aquatic reservoir and a vector. A potential role of P. acanthamoebae as an agent of lower respiratory tract infection was initially suggested by its isolation within an Acanthamoeba sp. recovered from the water of a humidifier during the investigation of an outbreak of fever. Additional serological and molecular-based investigations further supported its pathogenic role, mainly in bronchiolitis, bronchitis, aspiration pneumonia and community-acquired pneumonia. P. acanthamoebae was shown to survive and replicate within human macrophages, lung fibroblasts and pneumocytes. Moreover, this strict intracellular bacterium also causes severe pneumonia in experimentally infected mice, thus fulfilling the third and fourth Koch criteria for a pathogenic role. Consequently, new tools have been developed for the diagnosis of parachlamydial infections. It will be important to routinely search for this emerging agent of pneumonia, as P. acanthamoebae is apparently resistant to quinolones, which are antibiotics often used for the empirical treatment of atypical pneumonia. Other Chlamydia-related bacteria, including Protochlamydia naegleriophila, Simkania negevensis and Waddlia chondrophila, might also cause lung infections. Moreover, several additional novel chlamydiae, e.g. Criblamydia sequanensis and Rhabdochlamydia crassificans, have been discovered and are now being investigated for their human pathogenicity.

High Rate of Simkania negevensis among Canadian Inuit Infants Hospitalized with Lower Respiratory Tract Infections

To determine the prevalence of Simkania negevensis in causing pulmonary infections in children, nasopharyngeal washes were obtained from 22 infants hospitalized with acute bronchiolitis in the Baffin Island, Canada. 14 (63.6%) were positive for S. negevensis. Mixed infections with other respiratory viruses were common. All patients recovered without specific antibiotic treatment. Even though a high prevalence of S. negevensis was found, this organism may potentially well be an opportunistic agent rather than a true pathogen.

Amoeba co-culture of soil specimens recovered 33 different bacteria, including four new species and Streptococcus pneumoniae

Amoeba-resistant bacteria (ARB), such as Legionella spp., are currently regarded as potential human pathogens that live in the natural environment, and thus their habitat is regarded as a reservoir of human pathogens. To detect ARB in human and environmental samples, co-culture with amoebae has been demonstrated to be an efficient tool. However, to date, only water samples from cooling towers and hospital water supplies have been investigated as possible reservoirs of ARB using this procedure. In the present study, we studied the ARB population of 11 diverse soil and sand sources in proximity to human environments; these sources included the university, the station, hospitals, the square, parks and public beaches in the city of Marseilles, France. As a result, a total of 33 different species of ARB were identified. The ability to grow within and/or lyse amoebae was demonstrated, for what is believed to be the first time, for several species; moreover, 20 of the isolates (61%), including Streptococcus pneumoniae, have been described as human pathogens. However, Legionella spp. were not isolated. Four isolates are likely to be the members of new or uncharacterized genera or species, and their capability to be human pathogens needs to be determined. This preliminary work demonstrates that soils and sands in the vicinity of humans are reservoirs of human pathogenic ARB.

Diversity of the Parachlamydiae in the Environment

Chlamydiae are obligate intracellular bacteria, parasites of a variety of eukaryotes ranging from amoebae to humans. Among them, the family Parachlamydiaceae comprises endosymbionts of amoebae, mainly Acanthamoeba, currently investigated as emerging pathogens of humans and other vertebrates. 16S rDNA-based PCR culture-independent studies in environmental samples have demonstrated the presence of Chlamydiales in various types of nonmedical habitats. Here we reviewed the biology of the Parachlamydiaceae, and more particularly those studies reporting molecular evidences for their presence in the environment, with a re-analysis of the 16S rDNA phylotypes.

Evidence for Parachlamydia in bovine abortion

Bovine abortion of unknown infectious aetiology still remains a major economic problem. In this study, we focused on a new possible abortigenic agent called Parachlamydia acanthamoebae. Retrospective samples (n=235) taken from late-term abortions in cattle were investigated by real-time diagnostic PCR for Chlamydiaceae and Parachlamydia spp., respectively. Histological sections of cases positive by real-time PCR for any Chlamydia-related agent were further examined by immunohistochemistry using specific antibodies. Chlamydophila abortus was detected only in three cases (1.3%) by real-time PCR and ArrayTube Microarray playing a less important role in bovine abortion compared to the situation in small ruminants in Switzerland. By real-time PCR as many as 43 of 235 (18.3%) cases turned out to be positive for Parachlamydia. The presence of Parachlamydia within placental lesions was confirmed in 35 cases (81.4%) by immunohistochemistry. The main histopathological feature in parachlamydial abortion was purulent to necrotizing placentitis (25/43). Parachlamydia should be considered as a new abortigenic agent in Swiss cattle. Since Parachlamydia may be involved in lower respiratory tract infections in humans, bovine abortion material should be handled with care given the possible zoonotic risk.

Emerging role of Chlamydia and Chlamydia-like organisms in adverse pregnancy outcomes

PURPOSE OF THE REVIEW

This review considers the roles of Chlamydia spp. and newly identified Chlamydia-like organisms in miscarriage, stillbirths and preterm labour in both animals and humans.

RECENT FINDINGS

The cause of miscarriage, stillbirth and preterm labour often remains unexplained. Intracellular bacteria that grow either poorly or not at all on media used routinely to detect human pathogens could be the aetiological agents of these obstetrical conditions. There is growing evidence that Chlamydia trachomatis, Chlamydophila abortus, Chlamydophila psittaci and Chlamydophila pneumoniae infections may result in adverse pregnancy outcomes in humans and/or animals. Waddlia, a Chlamydia-like organism first isolated from an aborted bovine, has emerged as an agent of abortion in cattle. Recently, Waddlia was also implicated in human foetal death. Moreover, Parachlamydia acanthamoebae is also abortigenic in ruminants. Whether additional novel Chlamydia-like organisms, such as Protochlamydia amoebophila, Neochlamydia hartmanellae, Criblamydia sequanensis, Rhabdochlamydia crassificans and Simkania negevensis, are involved in foetal loss or premature delivery remains to be determined.

SUMMARY

This review provides an update on the consequences of chlamydial infection during pregnancy and summarizes current evidence suggesting that some Chlamydia-related organisms are probably emerging obstetrical pathogens.

Protochlamydia naegleriophila as etiologic agent of pneumonia

Using ameba coculture, we grew a Naegleria endosymbiont. Phenotypic, genetic, and phylogenetic analyses supported its affiliation as Protochlamydianaegleriophila sp. nov. We then developed a specific diagnostic PCR for Protochlamydia spp. When applied to bronchoalveolar lavages, results of this PCR were positive for 1 patient with pneumonia. Further studies are needed to assess the role of Protochlamydia spp. in pneumonia.

Parachlamydia spp. and related Chlamydia-like organisms and bovine abortion

Chlamydophila abortus and Waddlia chondrophila cause abortion in ruminants. We investigated the role of Parachlamydia acanthamoebae in bovine abortion. Results of immunohistochemical analyses were positive in 30 (70%) of 43 placentas from which Chlamydia-like DNA was amplified, which supports the role of Parachlamydia spp. in bovine abortion.

Waddlia chondrophila enters and multiplies within human macrophages

Waddlia chondrophila is an obligate intracellular bacterium of the Chlamydiales order. W. chondrophila has been isolated twice from aborted bovine foetuses and a serological study supported the abortigenic role of W. chondrophila in bovine species. Recently, we observed a strong association between the presence of anti-Waddlia antibodies and human miscarriage. To further investigate the pathogenic potential of W. chondrophila in humans, we studied the entry and the multiplication of this Chlamydia-like organism in human macrophages. Confocal and electron microscopy confirmed that W. chondrophila is able to enter human monocyte-derived macrophages. Moreover, W. chondrophila multiplied readily within macrophages. The proportion of infected macrophages increased from 13% at day 0 to 96% at day 4, and the mean number of bacteria per macrophage increased by 3logs in 24h. Intracellular growth of W. chondrophila was associated with a significant cytopathic effect. Thus, W. chondrophila may enter and grow rapidly within human macrophages, inducing lysis of infected cells. Since macrophages are one of the major components of the innate immune response, these findings indirectly suggest the possible human pathogenicity of W. chondrophila.

Isolation and identification of amoeba-resisting bacteria from water in human environment by using an Acanthamoeba polyphaga co-culture procedure

Amoeba-resisting bacteria (ARB) such as Legionella spp. are currently regarded as potential human pathogens living in the environment. To detect ARB from both human and environmental samples, co-culture with amoebae has been demonstrated as an efficient tool. However, using this procedure, mostly water from cooling towers and hospital water supplies have been investigated as the possible reservoir of ARB. In the present study, we studied ARB population in 77 environmental water samples including rivers, fountains, lakes and domestic wells in the south of France. As a result, a total of 244 isolates corresponding to 89 different species of ARB, but not Legionella spp., were identified. Ability to grow within and/or to be lytic for amoebae was revealed for the first time for several human pathogens. Six isolates are likely to be the members of a new or uncharacterized genus/species. An anaerobic bacterium, Clostridium frigidicarnis was demonstrated to be lytic for amoebae. This preliminary work demonstrates that the water environment in the vicinity of humans is a reservoir of ARB, including well-known pathogens for which amoebae and/or water was not recognized earlier as a possible reservoir.