Characterisation of Chlamydia psittaci isolated from a horse

Detection of Chlamydia species in 2 cases of equine abortion in Switzerland: a retrospective study from 2000 to 2018

Species of genus Chlamydia are important pathogens of animals, with a worldwide distribution and broad host range. Some species, such as Chlamydia psittaci, also pose a zoonotic disease risk. Abortion is one of the many diseases that has been associated with chlamydial infections in animals, with most attention focused on the economic impacts to sheep production. The role of chlamydia in equine abortions is unknown. Using the family-specific 23S ribosomal RNA (rRNA) Chlamydiaceae real-time PCR, we tested 169 formalin-fixed, paraffin-embedded fetal membrane samples from 162 equine abortion cases collected between 2000 and 2018 in Switzerland. Two equine abortion cases (1.2%) tested positive for Chlamydiaceae. Further analyses by the species-specific 23S rRNA ArrayMate microarray and sequencing of a fragment of the 16S rRNA gene revealed C. abortus and C. psittaci. In both cases, equine herpesvirus 1 was also present, which might have been the abortion cause, alone or in synergy with Chlamydia. The prevalence of abortigenic chlamydial species in equine abortion cases in our study was significantly lower than rates described elsewhere. Zoonotic chlamydial agents present in equine fetal membranes nevertheless should be considered a potential risk to humans during foaling, abortion, or stillbirth.

Detection of chlamydiae from the upper respiratory tract of healthy and diseased draught equines

The present investigation was conducted to study the prevalence and molecular characterization of chlamydiae associated with the respiratory infections of equines in the Sub-Himalayan region of India. Equine nasal swab samples (119) from 20 diseased and 99 apparently healthy equines were collected and tested by family Chlamydiaceae specific nested PCR based on ompA gene, besides 89 serum samples for AGPT. The molecular characterization of chlamydial species/strains was done by analyzing variation in VD II region of ompA gene. The chlamydia infections were detected in 48.74% of the nasal swabs (55% in diseased and 47.47% in apparently healthy animals) by nested PCR. Prevalence of two genetically variant strains of Chlamydia abortus and a single strain of Chlamydia psittaci was detected. AGPT showed 4.49% seropositive equines. High prevalence of chlamydiae was found among equines in the Sub-Himalayan region of India in Himachal Pradesh in both healthy and diseased equines.

The Genetic Transformation of Chlamydia pneumoniae

We demonstrate the genetic transformation of Chlamydia pneumoniae using a plasmid shuttle vector system which generates stable transformants. The equine C. pneumoniae N16 isolate harbors the 7.5-kb plasmid pCpnE1. We constructed the plasmid vector pRSGFPCAT-Cpn containing a pCpnE1 backbone, plus the red-shifted green fluorescent protein (RSGFP), as well as the chloramphenicol acetyltransferase (CAT) gene used for the selection of plasmid shuttle vector-bearing C. pneumoniae transformants. Using the pRSGFPCAT-Cpn plasmid construct, expression of RSGFP in koala isolate C. pneumoniae LPCoLN was demonstrated. Furthermore, we discovered that the human cardiovascular isolate C. pneumoniae CV-6 and the human community-acquired pneumonia-associated C. pneumoniae IOL-207 could also be transformed with pRSGFPCAT-Cpn. In previous studies, it was shown that Chlamydia spp. cannot be transformed when the plasmid shuttle vector is constructed from a different plasmid backbone to the homologous species. Accordingly, we confirmed that pRSGFPCAT-Cpn could not cross the species barrier in plasmid-bearing and plasmid-free C. trachomatis, C. muridarum, C. caviae, C. pecorum, and C. abortus However, contrary to our expectation, pRSGFPCAT-Cpn did transform C. felis Furthermore, pRSGFPCAT-Cpn did not recombine with the wild-type plasmid of C. felis Taken together, we provide for the first time an easy-to-handle transformation protocol for C. pneumoniae that results in stable transformants. In addition, the vector can cross the species barrier to C. felis, indicating the potential of horizontal pathogenic gene transfer via a plasmid.IMPORTANCE The absence of tools for the genetic manipulation of C. pneumoniae has hampered research into all aspects of its biology. In this study, we established a novel reproducible method for C. pneumoniae transformation based on a plasmid shuttle vector system. We constructed a C. pneumoniae plasmid backbone shuttle vector, pRSGFPCAT-Cpn. The construct expresses the red-shifted green fluorescent protein (RSGFP) fused to chloramphenicol acetyltransferase in C. pneumoniaeC. pneumoniae transformants stably retained pRSGFPCAT-Cpn and expressed RSGFP in epithelial cells, even in the absence of chloramphenicol. The successful transformation in C. pneumoniae using pRSGFPCAT-Cpn will advance the field of chlamydial genetics and is a promising new approach to investigate gene functions in C. pneumoniae biology. In addition, we demonstrated that pRSGFPCAT-Cpn overcame the plasmid species barrier without the need for recombination with an endogenous plasmid, indicating the potential probability of horizontal chlamydial pathogenic gene transfer by plasmids between chlamydial species.

[Microbiological diagnosis of infections due to Chlamydia spp. and related species]

Until recently the number of completed genomes belonging to Chlamydia trachomatis was very low, despite its importance in Public Health. Now, there are currently sixty-six completed genomes of C.trachomatis sequenced in different parts of the world. This genomic revolution has helped in understanding its biology, as well as improved the sensitivity and specificity in the diagnosis, and the development of epidemiological tools, not only for in C.trachomatis, but also for related species such as C.pneumoniae and C.psittaci. The diagnosis based on cell culture, serology and microimmunofluorescence is gradually being replaced by molecular techniques based on PCR or real-time PCR. This is because these molecular tests do not have cross-reactions problems and the procedures are easily standardised between laboratories. Moreover, molecular epidemiology tools described recently, such as Multi-Locus Sequence Typing (MLST) and Variable Number Tandem Repeat (VNTR), have increased our knowledge on local and global epidemiology. This article focuses on the impact of the genomics advances achieved over the last few years as applied to the diagnosis, epidemiology and biology of the family Chlamydiaceae family and related species.

Detection of Chlamydophila pneumoniae in cats with conjunctivitis

OBJECTIVE

To determine the presence of chlamydial species including recently described chlamydial agents as well as the human pathogen Chlamydophila pneumoniae in feline conjunctivitis.

ANIMAL STUDIED

Twenty five cats without and 49 cats with conjunctivitis were tested for chlamydia using a Chlamydiaceae real time (RT) PCR (targeting the 23S rRNA gene sequence), a Chlamydiales PCR (targeting the 16S rRNA gene sequence), and cell culture. The PCR products of all positive samples were sequenced and subsequently analyzed using a basic local alignment search tool search.

RESULTS

Chlamydiaceae RT PCR and subsequent sequence analyses identified C. pneumoniae in five cats in the conjunctivitis group. The presence of Chlamydophila felis was shown in two cats with conjunctivitis. Chlamydiae related to uncultured members of Chlamydiales were detected in three conjunctivitis cases and in one cat without clinical symptoms.

CONCLUSION

This study detects for the first time, the known human pathogen C. pneumoniae in feline conjunctivitis cases using Chlamydiaceae RT PCR and sequence analyses.

The Swedish new variant of Chlamydia trachomatis

PURPOSE OF REVIEW

This review focuses on the anatomy of the Swedish new variant of Chlamydia trachomatis (nvCT). This information provides an interesting insight into the emergence of new strains (how, where, and when), and the important lessons learned are discussed.

RECENT FINDINGS

In late 2006, the nvCT was first reported in Sweden; it carries a 377 bp deletion within its plasmid which covers the single targets originally used by Roche and Abbott diagnostic systems. The nvCT spread rapidly with thousands of falsely negative diagnoses. Genome sequencing and phenotypic characterization showed that the biological fitness of nvCT when compared with wild-type CT in vitro is unaltered. Therefore, the rapid transmission of nvCT was due to the selective advantage gained from failed diagnosis and the introduction of nvCT into a high-frequency transmitting population. The proportions of nvCT cases are now converging toward equilibrium with the wild-type CT strains. Interestingly, the nvCT remains rarely reported beyond the Nordic countries.

SUMMARY

The spread of nvCT had a substantial impact on C. trachomatis identification, epidemiology, and public health in Sweden. Lessons learned from this experience include the importance of investigating the incidence and epidemiology of infection in detail, the frequent participation in appropriate quality assurance schemes, and the careful design of diagnostic assays. The nvCT presents a unique opportunity to study the spread of a single C. trachomatis strain within both the human and bacterial populations; this may substantially increase our knowledge of epidemiology and transmission of chlamydial infections, and other sexually transmitted infections.

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

Background

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

Results

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

Conclusions

We have identified strain-specific differences and targets for detection of C. pneumoniae isolates from both human and animal origin. Such characterisation is necessary for an improved understanding of disease transmission and intervention.

Chlamydia pneumoniae is genetically diverse in animals and appears to have crossed the host barrier to humans on (at least) two occasions

Chlamydia pneumoniae is a common human and animal pathogen associated with a wide range of diseases. Since the first isolation of C. pneumoniae TWAR in 1965, all human isolates have been essentially clonal, providing little evolutionary insight. To address this gap, we investigated the genetic diversity of 30 isolates from diverse geographical locations, from both human and animal origin (amphibian, reptilian, equine and marsupial). Based on the level of variation that we observed at 23 discreet gene loci, it was clearly evident that the animal isolates were more diverse than the isolates of human origin. Furthermore, we show that C. pneumoniae isolates could be grouped into five major genotypes, A-E, with A, B, D and E genotypes linked by geographical location, whereas genotype C was found across multiple continents. Our evidence strongly supports two separate animal-to-human cross species transfer events in the evolutionary history of this pathogen. The C. pneumoniae human genotype identified in the USA, Canada, Taiwan, Iran, Japan, Korea and Australia (non-Indigenous) most likely originated from a single amphibian or reptilian lineage, which appears to have been previously geographically widespread. We identified a separate human lineage present in two Australian Indigenous isolates (independent geographical locations). This lineage is distinct and is present in Australian amphibians as well as a range of Australian marsupials.

Chlamydia pneumoniae is an intracellular bacterial pathogen with an extremely diverse host range (humans, amphibians, reptiles and marsupials). We selected 23 target genes in order to investigate genetic diversity: seven of these had been lost or gained by C. pneumoniae, a further six were conserved, four were polymorphic (defined by greater than 20 SNPs per 1 kbp; in this study), and six were truncated or length polymorphic in one strain or the other. Our research highlights that C. pneumoniae animal isolates are much more genetically diverse than C. pneumoniae human isolates, and have crossed the host barrier to humans on at least two occasions. Our study provides new insights into the evolution of this complex pathogen.

Detection of Chlamydophila caviae and Streptococcus equi subsp. zooepidemicus in horses with signs of rhinitis and conjunctivitis

At a stud farm of Trakehner horses, all 33 foals of a birth cohort developed conjunctivitis and serous to muco-purulent rhinitis, and 7 older horses showed recurrent signs of conjunctivitis. Examination of nasal and conjunctival swabs by bacterial and cell culture, as well as real-time PCR, ArrayTube microarray analysis and DNA sequencing led to the identification of Chlamydophila (C.) caviae (first description in horses) and Streptococcus (S.) equi subsp. zooepidemicus. We presume a synergistic effect associated with these two agents by hypothesising that primary lesions were set by C. caviae and subsequently aggravated by Streptococcus equi subsp. zooepidemicus. Indications supporting this assumption include (i) the conjunctivitis caused by mono-infection with C. caviae, (ii) recurrent clinical symptoms in the affected animals, and (iii) the absence of a sustained clinical effect of antibiotic therapy with trimethoprim-sulfonamide, enrofloxacin and amoxicillin. The detection of C. caviae in horses raises questions about the significance and natural host range of this agent.

Emerging Chlamydial Infections

Chlamydiae are important intracellular bacterial pathogens of vertebrates. In the last years, novel members of this group have been discovered: Parachlamydia acanthamoebae and Simkania negevensis seems to be emerging respiratory human pathogens, while Waddlia chondrophila might be a new agent of bovine abortion. Various species have been showed to infect also the herpetofauna and fishes, and some novel chlamydiae are endosymbionts of arthropods. In addition, molecular studies evidenced a huge diversity of chlamydiae from both environmental and clinical samples, most of such a diversity could be formed by novel lineages of chlamydiae. Experimental studies showed that free-living amoebae may support multiplication of various chlamydiae, then could play an important role as reservoir/vector of chlamydial infections. Here we reviewed literature data concerning chlamydial infections, with a particular emphasis on the novely described chlamydial organisms.

Unusual transmission route of Lymphogranuloma venereum; following sexual contact with a female donkey

Here, we present a 20-year-old man who presented with painful inguinal and femoral masses. He gave a history of sexual contact with a mare 14 days before his recent illness. He was diagnosed with lymphogranuloma venereum based on the histopathological findings and a high titre of IgG (1:1400).

High prevalence of chlamydial (Chlamydophila psittaci) infection in fetal membranes of aborted equine fetuses

Seventy-seven cases of equine abortion from 49 Hungarian farms that occurred between 1998 and 2000 were investigated for the presence of chlamydiae by immunohistochemistry, PCR and/or MZN staining. Evidence of the presence of these bacteria was obtained in 64 cases (83.1%) from 41 (83.7%) different farms. Partial ompA gene sequencing of PCR products revealed that the agent was Chlamydophila psittaci. Based on the findings of microbial diagnosis, pathology and case history, chlamydial infection was considered to be the most likely cause of abortion in at least 11 (14.3%) cases. In the remaining 53 Chlamydophila-positive cases, either other bacterial and viral agents (n = 22 or 28.6%) as well as non-infectious factors (n = 14 or 18.2%) were identified as more probable primary causes of disease, or the role of chlamydiae remained unclear because lesions in fetuses and fetal membranes were absent (n = 17 or 22.1%). When chlamydial antigen was detected in aborted equine placental tissue using immunohistochemistry it was seen only in the chorionic epithelial cells, but not in other parts of the fetal membranes nor in any of the fetal tissues. In conclusion, chlamydial infection of the genital tract should be considered a possible factor in equine reproductive disorders.

The plasmids of Chlamydia trachomatis and Chlamydophila pneumoniae (N16): accurate determination of copy number and the paradoxical effect of plasmid-curing agents

A 7·5 kbp cryptic plasmid is found in almost all isolates of Chlamydia trachomatis. Real-time PCR assays, using TaqMan chemistry, were set up to quantify accurately both the chlamydial plasmid and the single copy, chromosomal omcB gene in the infectious, elementary bodies (EBs) of C. trachomatis L1 440. Plasmid copy number was also determined in the EBs of six other lymphogranuloma venereum (LGV) isolates (serovars L1–L3), ten trachoma isolates (serovars A–C) and nine urogenital isolates (serovars D–J). The results indicated an average plasmid copy number of 4·0±0·8 (mean±95 % confidence interval) plasmids per chromosome. During the chlamydial developmental cycle, up to 7·6 plasmids per chromosome were detected, indicating an increased plasmid copy number in the actively replicating reticulate bodies. Attempts to eliminate the plasmid from strain L1 440 using the plasmid-curing agents ethidium bromide, acridine orange or imipramine/novobiocin led to a paradoxical increase in plasmid copy number. It is speculated that the stress induced by chemical curing agents may stimulate the activity of plasmid-encoded replication (Rep) proteins. In contrast to C. trachomatis, only a single isolate of Chlamydophila pneumoniae bears a plasmid. C. pneumoniae strain N16 supports a 7·4 kbp plasmid in which ORF1, encoding one of the putative Rep proteins, is disrupted by a deletion and split into two smaller ORFs. Similar assay techniques revealed 1·3±0·2 plasmids per chromosome (mean±95 % confidence interval) in EBs of this strain. These findings are in agreement with the hypothesis that the ORF1-encoded protein is involved in, but not essential for, plasmid replication and control of copy number.

Molecular evidence to support the expansion of the hostrange of Chlamydophila pneumoniae to include reptiles as well as humans, horses, koalas and amphibians

The Chlamydiales are a family of unique intracellular pathogens that cause significant disease in humans, birds and a wide range of animal hosts. Of the currently recognized species, Chlamydophila (previously Chlamydia) pneumoniae, unlike the other chlamydial species, has been previously considered to be solely a pathogen of humans, causing significant respiratory disease and has also been strongly connected with cardiovascular disease. Here we report the finding that strains of C. pneumoniae are widespread in the environment, being detected by molecular methods in a range of reptiles (snakes, iguanas, chameleons) and amphibians (frogs, turtles). Of particular interest was the finding that genotyping of the chlamydial major outer membrane protein gene in these newly identified C. pneumoniae strains showed that many were genetically very similar, if not identical to the human respiratory strains. Whether these reptilian and amphibian strains of C. pneumoniae are still capable of infecting humans, or crossed the host barrier some time ago, remains to be determined but may provide further insights into the relationship of this common respiratory infection with its human host.

Genetic characterization of a Chlamydophila pneumoniae isolate from an African frog and comparison to currently accepted biovars

The amphibian isolate DE177 identified as Chlamydophila (C.) pneumoniae was sequenced in five genomic regions: 16S ribosomal RNA gene, 16-23S intergenic spacer, ompA, ompB, and groESL genes. Comparison with corresponding sequences of the currently accepted equine, human and koala biovars of C. pneumoniae revealed that koala strains represented the most closely related taxon, although sequence dissimilarities in the ompA (VD4) and ompB gene regions were noted. In this respect, the present isolate is distinct from a previously described frog isolate (Berger et al., 1999) whose sequence analysis yielded identity to the koala biovar. As three of the nucleotide substitutions in ompA (VD4) of DE177 will be translated into two altered amino acids the possible existence of another biovar is discussed.

Evolutionary relationships among members of the genus Chlamydia based on 16S ribosomal DNA analysis

Nucleotide sequences from strains of the four species currently in the genus Chlamydia, C. pecorum, C. pneumoniae, C. psittaci, and C. trachomatis were investigated. In vitro-amplified RNA genes of the ribosomal small subunit from 30 strains of C. pneumoniae and C. pecorum were subjected to solid-phase DNA sequencing of both strands. The human isolates of C. pneumoniae differed in only one position in the 16S rRNA gene, indicating genetic homogeneity among these strains. Interestingly, horse isolate N16 of C. pneumoniae was found to be closely related to the human isolates of this species, with a 98.9% nucleotide similarity between their 16S rRNA sequences. The type strain and koala isolates of C. pecorum were also found to be very similar to each other, possessing two different 16S rRNA sequences with only one-nucleotide difference. Furthermore, the C. pecorum strains truncated the 16S rRNA molecule by one nucleotide compared to the molecules of the other chlamydial species. This truncation was found to result in loss of a unilaterally bulged nucleotide, an attribute present in all other eubacteria. The phylogenetic structure of the genus Chlamydia was determined by analysis of 16S rRNA sequences. All phylogenetic trees revealed a distinct line of descent of the family Chlamydiaceae built of two main clusters which we denote the C. pneumoniae cluster and the C. psittaci cluster. The clusters were verified by bootstrap analysis of the trees and signature nucleotide analysis. The former cluster contained the human isolates of C. pneumoniae and equine strain N16. The latter cluster consisted of C. psittaci, C. pecorum, and C. trachomatis. The members of the C. pneumoniae cluster showed tight clustering and strain N16 is likely to be a subspecies of C. pneumoniae since these strains also share some antigenic cross-reactivity and clustering of major outer membrane protein gene sequences. C. psittaci and strain N16 branched early out of the respective cluster, and interestingly, their inclusion bodies do not stain with iodine. Furthermore, they also share less reliable features like normal elementary body morphology and plasmid content. Therefore, the branching order presented here is very likely a true reflection of evolution, with strain N16 of the species C. pneumoniae and C. psittaci forming early branches of their respective cluster and with C. trachomatis being the more recently evolved species within the genus Chlamydia.

Plasmid diversity in Chlamydia

Chlamydiae exhibit low interspecies DNA homology and plasmids from different chlamydial species can be readily distinguished by Southern blot analysis and restriction enzyme profiling. In contrast, available plasmid sequence data from within the species Chlamydia trachomatis indicate that plasmids from human isolates are highly conserved. To evaluate the nature and extent of plasmid variation, the complete nucleotide sequences were determined for novel plasmids from three diverse non-human chlamydial isolates: pCpA1 from avian Chlamydia psittaci (N352); pCpnE1 from equine Chlamydia pneumoniae (N16); and pMoPn from C. trachomatis mouse pneumonitis. Comparison of the sequence data did not identify an overall biological function for the plasmid but did reveal considerable sequence conservation (> 60%) and a remarkably consistent genomic arrangement comprising eight major ORFs and four 22 bp tandem repeats. The plasmid sequences were close to 7500 nucleotides in length (pCpA1, 7553 bp; pMoPn, 7502 bp) however the equine C. pneumoniae plasmid was smaller (7362 bp) than all other chlamydial plasmids. The reduced size of this plasmid was due to a single large deletion occurring within ORF 1; this potentially generates two smaller ORFs. The disruption of ORF 1 is the only significant variation identified amongst the chlamydial plasmids and could prove important for future vector development studies.

Typing Chlamydia psittaci--a review of methods and recent findings

When the present chlamydial classification was established it was recognized that a wide variety of types were contained within the arbitrary designation Chlamydia psittaci. Early workers relied mostly on observations of growth characteristics to differentiate the types of C. psittaci isolated from a wide range of different hosts. The differences between isolates were confirmed serologically using a variety of tests of which the most sensitive was the micro-immunofluorescence (MIF) test which was able to recognize nine immunotypes among the mammalian isolates alone. This approach has recently been improved by the use of monoclonal antibodies in the MIF test which has confirmed most of the mammalian immunotypes and divided the avian strains into four groups. Studies on the nucleic acid of C. psittaci isolates show clear differences in the size distribution of DNA fragments produced by restriction endonuclease digestion of the genomes of the various types. Most importantly, studies of DNA/DNA homologies showed that at least four of the types identified by biological, serological and restriction endonuclease tests were sufficiently different to be considered separate species. Most recently, attention has been focused on DNA sequence comparisons of C. psittaci genes amplified by the polymerase chain reaction (PCR). The usual target has been the major outer membrane protein gene for which much sequence information is now available. The combination of PCR and MIF with monoclonals has provided a set of practical techniques with which all chlamydial isolates can be detected and typed with relative ease. It is likely that these developments will lead to the reclassification of the genus and, hopefully, a rapid increase of our understanding of the diseases caused by C. psittaci.