Immunoblotting, ELISA and culture evidence for Chlamydiaceae in sows on 258 Belgian farms

Characteristics of Chlamydia suis Ocular Infection in Pigs

Chlamydia (C.) suis can often be isolated from conjunctival swab specimens from pigs with conjunctivitis or keratoconjunctivitis. In the field, it is assumed to be a multifactorial disease triggered by immunosuppressing factors. This is the first experimental study to provoke clinical signs of conjunctivitis in pigs after C. suis primary mono-infection. Five six-week-old male piglets, free of ocular chlamydia shedding and seronegative for Chlamydia, were conjunctivally infected with the C. suis-type strain S45 (1 × 10⁹ inclusion forming units), while four piglets served as negative controls. The infection group developed clinical signs of conjunctivitis with a peak in the first week post-infection. Immunohistochemical evaluation revealed the presence of Chlamydia not only in the conjunctival epithelium, but also in the enlarged lacrimal glands, lungs, and intestine. No circulating antibodies could be detected during the whole study period of three weeks, although three different test systems were applied as follows: the complement fixation test, MOMP-based Chlamydiaceae ELISA, and PmpC-based C. suis ELISA. Meanwhile, high numbers of IFN-γ-producing lymphocytes within PBMC were seen after C. suis re-stimulation 14 days post-infection. Hence, these data suggest that entry via the eye may not elicit immunological responses comparable to other routes of chlamydial infections.

First Report of Chlamydia Seroprevalence in Farmed Wild Boars in China

Chlamydia is Gram-negative obligate bacterium, which can cause human diseases worldwide and has huge economic impact on animals. It is yet to know whether farmed wild boars are infected with Chlamydia in China. To assess risk factors of Chlamydia infection in farmed wild boars in China, from April 2015 to February 2016, a total of 837 serum samples of farmed wild boars were collected in Jilin province, northeastern China, and antibodies against Chlamydia were examined by the indirect hemagglutination assay. The investigation showed that antibodies to Chlamydia were detected in 332 (39.67%, 95% CI 33.36-42.98) of 837 serum samples of farmed wild boars, seroprevalence ranged from 33.71% to 44.42% among different regions and the differences were statistically significant by SPSS analysis (p = 0.0248). These results indicated that Chlamydia is highly prevalent in farmed wild boars in Jilin province, northeastern China, and may pose a potential risk for human health. To our knowledge, this is the first report of Chlamydia seroprevalence in farmed wild boars in China, which provided baseline data for preventing and controlling Chlamydia infection in wild boars in China.

Occurrence of reproductive disorders in pig herds with and without Chlamydia suis infection - statistical analysis of breeding parameters

Chlamydiae are frequently encountered Gram-negative intracellular eubacteria that can cause clear manifestations or clinically asymptomatic disorders. C. suis and other chlamydia are primarily isolated in cases of reproductive disorders. This study was performed to estimate the impact of Chlamydia suis infection on reproduction in sows by analyzing reproduction rates and breeding parameters. The test was conducted on first generation (F1) pigs from Polish Landrace (PL) × Polish Large White (PLW). Sixty-four herds were investigated and 500 vaginal swabs were collected. Isolation of DNA was carried out directly from the swabs. All samples were analyzed for Chlamydia suis by real-time PCR with a locked nucleic acid (LNA)-containing probe. To analyze the impact of chlamydia infection on reproductive parameters, evaluation questionnaires were used. Reproductive problems were found in 77.3% of the farms tested. The receiver operating characteristic curve indicated that in the farms with 10 up to 120 sows, there were higher reproductive problems with chlamydia infection than in smaller and bigger pig farms. The most common problems were estrus repetition, which was reported by 57.81% of the surveyed farms, and the birth of dead piglets, which was reported by 31.25% of the investigated pig farms. Abortions, which were reported by 28.12% of the surveyed farms, were the least common reproductive disorders.

Development of a Chlamydia suis-specific antibody enzyme-linked immunosorbent assay based on the use of a B-cell epitope of the polymorphic membrane protein C

Chlamydia suis infections lead to economic loss in the pork industry. Chlamydia suis infections could be successfully treated with tetracyclines until the appearance of a tetracycline resistant phenotype, which was acquired via horizontal gene transfer of the tet(C) gene. Given the importance of C. suis as a swine pathogen and as a recently emerged tetracycline resistant pathogen with zoonotic potential, our aim was to develop a sensitive C. suis-specific antibody ELISA based on the polymorphic membrane proteins (Pmps). Chlamydia Pmps are important virulence factors and candidate antigens for serodiagnosis. We identified nine Pmps (PmpA to I) in C. suis strain MD56 using a recently developed Hidden-Markov model. PmpC was the most promising candidate for the development of a C. suis-specific antibody ELISA as the protein was absent in C. abortus, C. pecorum and C. psittaci which also infect pigs and as the protein contained C. suis-specific amino acid regions, absent in C. trachomatis PmpC. We identified an immunodominant B-cell epitope in C. suis PmpC using experimental porcine sera. The sensitivity and specificity of the PmpC ELISA was compared to the complement fixation test (CFT) and to a recombinant MOMP ELISA using experimental sera. The PmpC ELISA detected all positive control sera and was in contrast to CFT and the rMOMP ELISA 100% C. suis specific as positive control sera against other Chlamydia species did not react in the PmpC ELISA. The test was successfully validated using slaughterhouse sera and sera from clinically affected pigs. The PmpC ELISA could assist in diminishing the spread of C. suis infections in the pork industry.

Asymptomatic infections with highly polymorphic Chlamydia suis are ubiquitous in pigs

Background

Chlamydia suis is an important, globally distributed, highly prevalent and diverse obligate intracellular pathogen infecting pigs. To investigate the prevalence and genetic diversity of C. suis in China, 2,137 nasal, conjunctival, and rectal swabs as well as whole blood and lung samples of pigs were collected in 19 regions from ten provinces of China in this study.

Results

We report an overall positivity of 62.4% (1,334/2,137) of C. suis following screening by Chlamydia spp. 23S rRNA-based FRET-PCR and high-resolution melting curve analysis and confirmatory sequencing. For C. suis-positive samples, 33.3 % of whole blood and 62.5% of rectal swabs were found to be positive for the C. suis tetR(C) gene, while 13.3% of whole blood and 87.0% of rectal swabs were positive for the C. suis tet(C) gene. Phylogenetic comparison of partial C. suis ompA gene sequences revealed significant genetic diversity in the C. suis strains. This genetic diversity was confirmed by C. suis-specific multilocus sequence typing (MLST), which identified 26 novel sequence types among 27 examined strains. Tanglegrams based on MLST and ompA sequences provided evidence of C. suis recombination amongst the strains analyzed.

Conclusions

Genetically highly diverse C. suis strains are exceedingly prevalent in pigs. As it stands, the potential pathogenic effect of C. suis on pig health and production of C. suis remains unclear and will be the subject of further investigations. Further study is also required to address the transmission of C. suis between pigs and the risk of 'spill-over' and 'spill-back' of infections to wild animals and humans.

Electronic supplementary material

The online version of this article (10.1186/s12917-017-1295-x) contains supplementary material, which is available to authorized users.

Chlamydia prevalence in Polish pig herds

Chlamydiae are frequently encountered intracellular Gram-negative bacteria. In pigs, these bacteria in combination with other pathogens contribute to the induction of a multi-aetiological syndrome. One of the major characteristics of Chlamydia spp. is their ability to cause prolonged, often subclinical infections. While the economic consequences of Chlamydia spp. infections in pig farms are not fully established, we know that reproductive disorders and other syndromes correlated with Chlamydia infection can lead to financial loss as a result of a reduction in pork production. Additionally, Chlamydia spp. presents a potential zoonotic hazard, therefore determining the prevalence of Chlamydia in pig populations is critical. In the present study 97 pig herds from Poland were involved. To determine the prevalence of Chlamydia PCR and CFT tests were used. In total 797 vaginal samples, 797 conjunctival samples, and 235 serum samples were collected and tested. The study took place from 2011 to 2014. We found Chlamydia spp. present in 71·2% of all tested farms. The percentage of animals testing positive on any given farm varied from 20% to 100%.

Prevalence of Chlamydial Infections in Fattening Pigs and Their Influencing Factors

Chlamydial infections in pigs are associated with respiratory disease, diarrhea, conjunctivitis and other pathologies. The aim of this study was to define the prevalence of Chlamydiaceae in Swiss fattening pigs by applying sensitive and specific detection methods and to correlate prior antibiotic treatment and farm related factors with differences in prevalence. Conjunctival and fecal swabs were collected from 636 pigs in 29 Swiss fattening pig farms with and without antibiotic treatment, at the beginning and the end of the fattening period. The swabs were screened by real-time PCR for Chlamydiaceae. For the chlamydial detection and species-identification, a DNA-microarray analysis was performed. All farms were positive for Chlamydiaceae with 94.3 and 92.0% prevalence in fecal swabs as well as 45.9 and 32.6% in conjunctival swabs at the first and second time points, respectively. Antibiotic treatment could not clear the infection on herd level. Potential contact with wild boars was a significant risk factor, while hygiene criteria did not influence chlamydial prevalence. A correlation of chlamydial positivity to diarrhea, but not to conjunctivitis was evident. Chlamydia suis was the predominant species. Mixed infections with C. suis and C. pecorum were common, with a substantial increase in C. pecorum positivity at the end of the fattening period, and this finding was associated with ruminant contact. C. abortus was detected in one conjunctival swab. In this study, C. suis inhabited the intestinal tract of nearly all examined pigs, implying a long-term infection. C. pecorum was also common and might be transmitted to pigs by ruminants.

Assessment of Chlamydia suis Infection in Pig Farmers

Chlamydia suis infections are endemic in domestic pigs in Europe and can lead to conjunctivitis, pneumonia, enteritis and reproductive failure. Currently, the knowledge on the zoonotic potential of C. suis is limited. Moreover, the last decades, porcine tetracycline resistant C. suis strains have been isolated, which interfere with treatment of chlamydial infections. In this study, the presence of C. suis was examined on nine Belgian pig farms, using Chlamydia culture and a C. suis specific real-time PCR in both pigs and farmers. In addition to diagnosis for C. suis, the farmers' samples were examined using a Chlamydia trachomatis PCR. Additionally, the Chlamydia isolates were tested for the presence of the tet(C) resistance gene. C. DNA was demonstrated in pigs on all farms, and eight of nine farmers were positive in at least one anatomical site. None of the farmers tested positive for C. trachomatis. Chlamydia suis isolates were obtained from pigs of eight farms. Nine porcine C. suis isolates possessing a tet(C) gene were retrieved, originating from three farms. Moreover, C. suis isolates were identified in three human samples, including one pharyngeal and two rectal samples. These findings suggest further research on the zoonotic transfer of C. suis from pigs to humans is needed.

Chlamydia psittaci: update on an underestimated zoonotic agent

Chlamydia (C.) psittaci is an economically relevant pathogen in poultry and pet birds, where it causes psittacosis/ornithosis, and also a human pathogen causing atypical pneumonia after zoonotic transmission. Despite its well-documented prevalence, the agent has received less attention by researchers than other Chlamydia spp. in the last decades. In the present paper, we review recently published data on C. psittaci infection and attempt to single out characteristic features distinguishing it from related chlamydial agents. It is remarkable that C. psittaci is particularly efficient in disseminating in the host organism causing systemic disease, which occasionally can take a fulminant course. At the cellular level, the pathogen's broad host cell spectrum (from epithelial cells to macrophages), its rapid entry and fast replication, proficient use of intracellular transport routes to mitochondria and the Golgi apparatus, the pronounced physical association of chlamydial inclusions with energy-providing cell compartments, as well as the subversive regulation of host cell survival during productive and persistent states facilitate the characteristic efficient growth and successful host-to-host spread of C. psittaci. At the molecular level, the pathogen was shown to upregulate essential chlamydial genes when facing the host immune response. We hypothesize that this capacity, in concert with expression of specific effectors of the type III secretion system and efficient suppression of selected host defense signals, contributes to successful establishment of the infection in the host. Concerning the immunology of host-pathogen interactions, C. psittaci has been shown to distinguish itself by coping more efficiently than other chlamydiae with pro-inflammatory mediators during early host response, which can, to some extent, explain the effective evasion and adaptation strategies of this bacterium. We conclude that thorough analysis of the large number of whole-genome sequences already available will be essential to identify genetic markers of the species-specific features and trigger more in-depth studies in cellular and animal models to address such vital topics as treatment and vaccination.

Novel locked nucleic acid (LNA)-based probe for the rapid identification of Chlamydia suis using real-time PCR

Background

As the importance of chlamydial infections in pigs has become more obvious, a rapid and sensitive method to study the prevalence of Chlamydia suis in pig herds is required. Such a method should permit routine diagnostic tests for herds with clinical and subclinical infections, without the need for Chlamydia culture.

Results

The main objective of this study was to develop a specific and rapid method for detecting C. suis in swine herds. A real-time PCR assay using a single locked nucleic acid (LNA)-containing probe specific for C. suis was developed based on the previously described 28S rDNA fragment used to identify Chlamydiales. Use of LNA nucleotides enabled the single probe to target a short, specific fragment of the 23S rRNA. The probe showed high specificity for C. suis and did not show any cross-reactivity with other Chlamydia or Chlamydophila species nor with swine DNA. All of the 86 tested field isolates, earlier identified as C. suis, were confirmed as positive using the newly developed assay.

Conclusions

Using single LNA-based C. suis-specific probe allowed rapid and simple identification of this pathogen without requiring sequencing analysis and culturing. The proposed method may be used to study the prevalence of C. suis infection in pig herds and as a routine diagnostic test for herds with clinical and subclinical infection.

Rapid detection of Chlamydia/Chlamydophila group in samples collected from swine herds with and without reproductive disorders

The study was carried out in seven reproductive herds of pigs. In three of them reproductive disorders were observed. Three herds consisted of 10-50 and four consisted of 120-500 adult sows and they were called small and medium, respectively. Fifty-seven adult sows were randomly selected from herds. Serum samples were tested using the complement fixation test and swabs from both eyes and from the vaginal vestibule were examined using real-time PCR. All serum samples were negative. Infected sows were present in each of the study herds. In total, there were 28 positive samples (53%, 28/48) in real-time PCR in sows with reproductive disorders and 35 (53%, 35/66) in sows selected from herds without problems in reproduction. One isolate proved to be Chlamydophila pecorum, whereas all the remaining were Chamydia suis

Development and validation of a real-time PCR for Chlamydia suis diagnosis in swine and humans

Pigs are the natural host for Chlamydia suis, a pathogen which is phylogenetically highly related to the human pathogen C. trachomatis. Chlamydia suis infections are generally treated with tetracyclines. In 1998, tetracyline resistant C. suis strains emerged on U.S. pig farms and they are currently present in the Belgian, Cypriote, German, Israeli, Italian and Swiss pig industry. Infections with tetracycline resistant C. suis strains are mainly associated with severe reproductive failure leading to marked economical loss. We developed a sensitive and specific TaqMan probe-based C. suis real-time PCR for examining clinical samples of both pigs and humans. The analytical sensitivity of the real-time PCR is 10 rDNA copies/reaction without cross-amplifying DNA of other Chlamydia species. The PCR was successfully validated using conjunctival, pharyngeal and stool samples of slaughterhouse employees, as well as porcine samples from two farms with evidence of reproductive failure and one farm without clinical disease. Chlamydia suis was only detected in diseased pigs and in the eyes of humans. Positive humans had no clinical complaints. PCR results were confirmed by culture in McCoy cells. In addition, Chlamydia suis isolates were also examined by the tet(C) PCR, designed for demonstrating the tetracycline resistance gene tet(C). The tet(C) gene was only present in porcine C. suis isolates.

Seroprevalence of Chlamydia infection in pigs in Jiangxi province, south-eastern China

Chlamydia are Gram-negative obligate bacteria that cause a wide range of diseases in humans and animals. To assess the risk of zoonosis posed by pigs, a total of 920 serum samples were collected from pigs in 11 administrative cities in Jiangxi province, south-eastern China, and the seroprevalence of Chlamydia antibodies was investigated by an indirect haemagglutination assay. The pathogen-specific antibodies were detected in 539 (58.59 %) pigs with seroprevalence ranging from 33.33 % (Jingdezhen) to 90.91 % (Pingxiang) among different cities (P<0.05). The highest prevalence was found in pregnant sows (80.89 %, 127/157), followed by breeding boars (79.37 %, 50/63), suckling sows (77.01 %, 67/87), fattening pigs (69.32 %, 61/88) and non-pregnant sows (62.5 %, 180/288). Piglets had the lowest prevalence of 22.78 % (54/237). The seroprevalence of Chlamydia infection among different categories of pigs was also significantly different (P<0.05). These results indicate that Chlamydia is highly prevalent in pigs in Jiangxi province and our results indicate that the presence of Chlamydia exposure in pigs may pose a potential threat to human health.

First report of Chlamydiaceae seroprevalence in Tibetan pigs in Tibet, China

The seroprevalence of Chlamydiaceae infection in Tibetan pigs in Tibet, China, was examined by indirect hemagglutination assay (IHA), between April, 2010, and December, 2010. A total of 71 of 427 serum samples (16.63%, 95% confidence interval [CI] 15.31-17.95] were positive for Chlamydiaceae antibodies. Forty Chlamydiaceae seropositives from 232 samples were recorded in sera from Nyingchi (17.24%, 95% CI 15.40-19.08) and 31 positives were recorded in 195 serum samples from Mainling (15.90%, 95% CI 14.02-17.78). The investigation showed that the prevalence in female animals was 17.61% (95% CI 15.22-20.00), and in male animals it was 12.72% (95% CI 11.07-14.37). The prevalence ranged from 0% to 20.61% (95% CI 17.81-23.48) among different age groups, with a higher prevalence in growing pigs (p<0.01). The results indicated that Chlamydiaceae infection was widespread in Tibetan pigs in Tibet, China, which is of public health concern in this region of the world. To our knowledge, this is the first report of Chlamydiaceae seroprevalence in Tibetan pigs in Tibet, China.

Genome Sequence of Chlamydia psittaci Strain 01DC12 Originating from Swine

Chlamydia psittaci is the etiological agent of psittacosis and is a zoonotic pathogen infecting birds and a variety of mammalian hosts. Here we report the genome sequence of the porcine strain 01DC12 which is representative of a novel clade of C. psittaci belonging to ompA genotype E.

Chlamydiaceae infections in pig

Chlamydiaceae are Gram-negative obligate intracellular bacteria. They are responsible for a broad range of diseases in animals and humans. In pigs, Chlamydia suis, Chlamydia abortus, Chlamydia pecorum and Chlamydia psittaci have been isolated. Chlamydiaceae infections in pigs are associated with different pathologies such as conjunctivitis, pneumonia, pericarditis, polyarthritis, polyserositis, pseudo-membranous or necrotizing enteritis, periparturient dysgalactiae syndrome, vaginal discharge, return to oestrus, abortion, mummification, delivery of weak piglets, increased perinatal and neonatal mortality and inferior semen quality, orchitis, epididymitis and urethritis in boars. However, Chlamydiaceae are still considered as non-important pathogens because reports of porcine chlamydiosis are rare. Furthermore, Chlamydiaceae infections are often unnoticed because tests for Chlamydiaceae are not routinely performed in all veterinary diagnostic laboratories and Chlamydiaceae are often found in association with other pathogens, which are sometimes more easily to detect. However, recent studies have demonstrated that Chlamydiaceae infections in breeding sows, boars and piglets occur more often than thought and are economically important. This paper presents an overview on: the taxonomy of Chlamydiaceae occurring in pigs, diagnostic considerations, epidemiology and pathology of infections with Chlamydiaceae in pigs, public health significance and finally on prevention and treatment of Chlamydiaceae infections in pigs.

Possible pathogenic interplay between Chlamydia suis, Chlamydophila abortus and PCV-2 on a pig production farm

A concurrent outbreak of chlamydial disease in boars, sows and gilts and postweaning multisystemic wasting syndrome (PMWS) in weaned piglets was investigated on a large pig production farm in Estonia. Chlamydia suis DNA was detected in conjunctival swabs from boars, sows and gilts, but also in the faeces of boars and sows. Chlamydophila abortus DNA was found in semen, and in conjunctival swabs from sows; DNA was demonstrated by microarrays. Serum samples from boars were examined using a Chlamydiaceae-specific recombinant ELISA. All 10 serum samples examined were positive (1:960 to 1:3840). Chlamydiosis was characterised by reproductive failure and conjunctivitis. Piglets were not examined for Chlamydiaceae, as eye problems were not observed. Piglets showed wasting, respiratory signs, diarrhoea, enlargement of lymph nodes and increased mortality (10 per cent). Porcine circovirus type 2 (PCV-2) was detected in the lymph nodes of piglets by immunohistochemistry, and PCV-2 antibodies were demonstrated in all 10 serum samples from sows examined using an immunoperoxidase monolayer assay.

Recent developments in the laboratory diagnosis of chlamydial infections

There are two main approaches to diagnosing infections by Chlamydia and Chlamydophila spp. in mammals and birds. The first involves the direct detection of the agent in tissue or swab samples, while the second involves the serological screening of blood samples for the presence of anti-chlamydial antibodies. Ultimately, the test that is used is dependent on the types of samples that are submitted to the diagnostic laboratory for analysis. The present paper gives an overview on methodologies and technologies used currently in diagnosis of chlamydial infections with emphasis on recently developed tests. The performance characteristics of individual methods, such as the detection of antigen in smears and in pathological samples, the isolation of the pathogen, various antibody detection tests and DNA-based methods utilising conventional and real-time PCR, as well as DNA microarray technology are assessed, and specific advantages and drawbacks are discussed. Further, a combination of a specific real-time PCR assay and a microarray test for chlamydiae is proposed as an alternative reference standard to isolation by cell culture.

Molecular evidence for chlamydial infections in the eyes of sheep

Ocular infections by chlamydiae are associated with ocular disease manifestations such as conjunctivitis and keratitis in humans and animals. Limited evidence exists that members of the order Chlamydiales can also cause ocular disease in sheep. In the current study, the prevalence of chlamydiae in the eyes of sheep was investigated by using PCR methods. Data obtained in sheep by broad-range 16S rRNA order Chlamydiales-specific PCR were compared to the prevalence of antibodies against chlamydiae detected by a competitive enzyme-linked immunosorbent assay (cELISA). Flocks tested included a clinically healthy flock and two flocks suffering from ocular disease and with histories of Ovine Enzootic Abortion (OEA). PCR detected DNA of Chlamydophila (Cp.) abortus and Cp. pecorum in the eyes of both healthy and sick animals but also identified Chlamydia (C.) suis and a variety of uncultured chlamydia-like organisms. Good correlation was found between the presence of Cp. abortus DNA in sheep conjunctival samples and seropositivity detected by cELISA. Despite these findings, no association was found between the presence of chlamydial DNA in the sheep conjunctival samples and the onset of clinical disease. These results suggest that the biodiversity of chlamydiae in the eyes of sheep is greater than that previously thought. Further investigations are needed to determine whether a causal relationship between infection by chlamydiae and ocular disease exists in these animals.

The prevalence of chlamydiae of bulls from six bull studs in Germany

Although there are indications for venereal transmission of chlamydiae in cattle, epidemiological data on the presence of these bacteria in bulls and bull semen in particular is still incomplete. We investigated semen (n=120), preputial washing samples (n=121) and faeces (n=122) of bulls from six bull studs located within five Federal States of Germany for the presence of chlamydiae using omp1-PCR and partial omp1 sequencing. Blood serum was examined for chlamydial antibodies using an indirect ELISA (n=122). Chlamydiae were found in 11 (9.2%), 13 (10.7%) and 22 (18.0%) of the semen, preputial washing and faecal samples, respectively. Among individual chlamydial species identified, Chlamydophila (Cp.) psittaci predominated in semen and preputial washing samples, and Cp. pecorum in faeces. Cp. abortus was the third frequently observed species. Chlamydial antibodies were detected in a total of 62 (50.8%) bulls. Bull studs differed in regard to the number of bulls found chlamydia-positive in faeces and serologically positive. No correlation was observed between serological data and PCR of semen, preputial washing samples or faeces. Standard ejaculate parameters did not differ between bulls that were chlamydia-positive and -negative in semen. In conclusion, detection of chlamydiae in semen of bulls suggests a potential for venereal transmission. Chlamydiae appear to be widespread within the bull population in Germany. Serological testing failed to identify bulls shedding chlamydiae in their semen.

Transcriptional response patterns of Chlamydophila psittaci in different in vitro models of persistent infection

The obligatory intracellular bacterium Chlamydophila psittaci is the causative agent of psittacosis in birds and humans. The capability of this zoonotic pathogen to develop a persistent phase is likely to play a role in chronicity of infections, as well as in failure of antibiotic therapy and immunoprophylaxis. To elucidate three different in vitro models for transition of C. psittaci to persistence (iron depletion, penicillin G treatment, and gamma interferon [IFN-gamma] exposure), a set of 27 genes was examined by mRNA expression analysis using quantitative real-time PCR. While the phenotypical characteristics were the same as in other chlamydiae, i.e., aberrant morphology of reticulate bodies, loss of cultivability, and rescue of infectivity upon removal of inducers, the transcriptional response of C. psittaci to persistence-inducing factors included several new and distinctive features. Consistent downregulation of membrane proteins, chlamydial sigma factors, cell division protein, and reticulate body-elementary body differentiation proteins from 24 h postinfection onward proved to be a general feature of C. psittaci persistence. However, other genes displayed considerable variations in response patterns from one model to another, which suggests that there is no persistence model per se. In contrast to results for Chlamydia trachomatis, late shutdown of essential genes in C. psittaci was more comprehensive with IFN-gamma-induced persistence, which is probably due to the absence of a functional tryptophan synthesis operon.

Detection of chlamydiae in boar semen and genital tracts

Chlamydiae cause abortion and reproductive disorders in sows. Although organisms can infect the male genital tract, little is known about the disease situation in boars. Hence, we examined the prevalence of chlamydial infection in semen and genital tracts of boars. Samples collected from Swiss boars (group A: n=42), and boars from Germany (group B: n=39) were examined by bacteriology, LPS-ELISA, immunohistochemistry (IHC) and polymerase chain reaction (PCR). The latter methodology involved use of three PCR assays including 16Sig rDNA, IGS-S (intergenic spacer 16S/23S-Short) and IGS-L (intergenic spacer 16S/23S-Long) PCR for comparison methods. PCR sensitivity and the presence of potential PCR inhibitors were determined by spiking semen with Chlamydophila (Cp.) abortus DNA. Detection limits of the 16Sig and IGS-S PCR were 10 templates, while the IGS-L PCR was less sensitive (100 templates). Of 25 semen samples that were collected from group A, one semen sample was positive for Cp. psittaci and two were positive for Chlamydia-like organisms by 16Sig PCR. Screening of sera from Swiss boars revealed three animals with positive reactions in the LPS-ELISA, although we failed to detect chlamydiae within organs of these or sera-negative animals by IHC or IGS-S PCR. In group B, 10 ejaculates were positive for Chlamydia (C.) suis and two were positive for Chlamydia-like organisms by 16S PCR. The identification of DNA from Chlamydia-like organisms in semen from both groups of boars was surprising and a role for these bacteria in reproductive diseases requires further assessment. In conclusion, the prevalence of chlamydial infection was low in group A animals indicating that venereal transmission may not be significant for Chlamydia-associated reproductive diseases in pigs, although rare cases may occur.

Prevalence of chlamydiae in boars and semen used for artificial insemination

Although there are indications for venereal transmission of chlamydiae in pigs, direct diagnostic evidence on the presence of these bacteria in boars and boar semen in particular is still incomplete. We investigated boars from two studs (A, B) in semen (A: n = 174; B: n = 100) and faeces (A: n = 174; B: n = 24) for chlamydiae using ompA-PCR and partial ompA gene sequencing. Additionally, blood serum was examined for chlamydial antibodies using an indirect ELISA (A: n = 171; B: n = 62). Chlamydiae were found in 9 (5.2%) and 24 (24.0%) semen specimens, and in 71 (40.1%) and 2 (8.3%) faecal samples from boars of stud A and B, respectively. Regarding individual chlamydial species, Chlamydophila psittaci and Chlamydia suis were identified most frequently, with the former predominating in semen (in 23 out of 33 positive samples) and the latter in faeces (68/73). In contrast, Chlamydophila pecorum was found only sporadically. Chlamydial antibodies were detected in 80 (46.8%) and 6 (9.7%) boars of stud A and B, respectively. No correlation was observed between the data from serology and PCR of semen or faeces in either of the studs. In conclusion, detection of chlamydiae in semen of boars suggests a potential for venereal transmission. Whether the high overall prevalence of chlamydial infections reflects a general situation in boars needs to be investigated. Serological testing failed to identify boars shedding chlamydiae in their semen.

Specific-pathogen-free pigs as an animal model for studying Chlamydia trachomatis genital infection

The purpose of the present study was to evaluate pigs as a large-animal model for female genital infection with two Chlamydia trachomatis human serovar E strains. Sixteen-week-old specific-pathogen-free female pigs (gilts) were intravaginally infected with the trachoma type E reference strain Bour or the urogenital serovar E strain 468. Several conclusions can be drawn from our findings on the pathogenicity of a primary C. trachomatis genital infection in gilts. First of all, we demonstrated that the serovar E strains Bour and 468 could ascend in the genital tract of gilts. The serovar E strains could replicate in the superficial columnar cervical epithelium and in the superficial epithelial layer of the uterus, which are known to be the specific target sites for a C. trachomatis genital infection in women. Second, inflammation and pathology occurred at the replication sites. Third, the organisms could trigger a humoral immune response, as demonstrated by the presence of immunoglobulin M (IgM), IgG, and IgA in both serum and genital secretion samples. Our findings imply that the pig model might be useful for studying the pathology, pathogenesis, and immune response to a C. trachomatis infection of the genital system.

Sequencing of the Chlamydophila psittaci ompA gene reveals a new genotype, E/B, and the need for a rapid discriminatory genotyping method

Twenty-one avian Chlamydophila psittaci isolates from different European countries were characterized using ompA restriction fragment length polymorphism, ompA sequencing, and major outer membrane protein serotyping. Results reveal the presence of a new genotype, E/B, in several European countries and stress the need for a discriminatory rapid genotyping method.

Occurrence of Chlamydiaceae spp. in a wild boar (Sus scrofa L.) population in Thuringia (Germany)

Tissue samples from lungs, pulmonary lymph nodes, large intestine, and uteri of 14 wild boar bagged at a seasonal hunt were examined for the presence of chlamydiae, mycobacteria and mycoplasmas. Nested PCR detected chlamydial DNA in 57.1% of the animals, predominantly in the lung. DNA sequencing identified Chlamydophila psittaci as the predominant species, but Chlamydophila abortus and Chlamydia suis were also encountered. Immunohistochemical staining of tissue sections confirmed the presence of typical chlamydial inclusions in lungs and uteri. While the role of Chlamydiaceae as pathogens in wild boar has yet to be established, the present findings revealed a possible wildlife reservoir of these bacteria.