Primary pathogenicity of an European isolate of Chlamydia psittaci from turkey poults

Chlamydia psittaci infected cell studies by 4Pi Raman and atomic force microscopy

Chlamydia psittaci is an avian bacterial pathogen that can cause atypical pneumonia in humans via zoonotic transmission. It is a Gram-negative intracellular bacterium that proliferates inside membrane bound inclusions in the cytoplasm of living eukaryotic cells. The study of such cells with C. psittaci inside without destroying them poses a significant challenge. We demonstrated in this work the utility of a combined multitool approach to analyze such complex samples. Atomic force microscopy was applied to obtain high-resolution images of the surface of infected cells upon entrance of bacteria. Atomic force microscopy scans revealed the morphological changes of the cell membrane of Chlamydia infected cells such as changes in roughness of cell membrane and the presence of micro vesicles. 4Pi Raman microscopy was used to image and probe the molecular composition of intracellular bacteria inside intact cells. Information about the structure of the inclusion produced by C. psittaci was obtained and it was found to have a similar molecular fingerprint as that of an intracellular lipid droplet but with less proteins and unsaturated lipids. The presented approach demonstrates complementarity of various microscopy-based approaches and might be useful for characterization of intracellular bacteria.

Human psittacosis: a review with emphasis on surveillance in Belgium

Chlamydia psittaci causes psittacosis in humans, mainly in persons in contact with birds in either the setting of occupational or companion bird exposure. Infection is associated with a range of clinical manifestations from asymptomatic infection to severe atypical pneumonia and systemic disease. This paper reviews new knowledge on psittacosis, its legal and regulatory aspects and presents epidemiological data on psittacosis in Belgium. In Belgium, the number of reported positive laboratory results increased slowly since 2010, and in 2017, the number almost doubled compared to the two previous years. The number of psittacosis cases in Belgium, as in other countries, is probably highly underestimated, because of underdiagnoses and underreporting. Over the 3-year period, the mandatory notification system registered 24% only of all reported positive laboratory result. Therefore, increased awareness among general and occupational physicians, clinicians and the public is needed. Policies aimed at reducing psittacosis disease burden are justified, nevertheless national health authorities should provide more legal and financial support to implement more adequate C. psittaci diagnostic tools.

Survey on Chlamydiaceae in cloacal swabs from Swiss turkeys demonstrates absence of Chlamydia psittaci and low occurrence of Chlamydia gallinacean

In Switzerland, domestic turkey meat is a niche product. Turkeys are fattened on mixed family-based farms scattered across the country, with most providing access to an uncovered outdoor pasture for the birds. Swiss fattening turkeys may therefore get infected with Chlamydiaceae via wild birds or their faeces, potentially shedding these bacteria at a later stage. The aim of the present study was to acquire baseline data about the shedding of Chlamydiaceae in clinically unremarkable Swiss fattening turkeys at slaughter, potentially exposing slaughterhouse workers to infection. In this large-scale study, 1008 cloacal swabs of Swiss turkeys out of 53 flocks from 28 different grow-out farms with uncovered outdoor pasture were collected over the course of 14 months and examined for the occurrence of Chlamydiaceae by a family-specific 23S-rRNA real-time PCR. Positive samples were further analyzed by Chlamydia psittaci (C. psittaci)-specific real-time PCR and the Arraymate DNA Microarray for species identification. All samples were negative for C. psittaci, but seven swabs out of one flock were tested positive for Chlamydia gallinacea (0.7%). Although turkeys with access to pasture may have contact with Chlamydiaceae-harbouring wild birds or their faeces, the infection rate in Swiss turkeys was shown to be low.

Risk assessment and management of Chlamydia psittaci in poultry processing plants

Chlamydia psittaci causes respiratory disease in poultry and can be transmitted to humans. Historical outbreaks of psittacosis in poultry workers indicated the need for higher awareness and an efficient risk assessment and management. This group reviewed relevant previous research, practical guidelines, and European directives. Subsequently, basic suggestions were made on how to assess and manage the risk of psittacosis in poultry processing plants based on a classical four-step approach. Collective and personal protective measures as well as the role of occupational medicine are described. Despite the finding that exposure is found in every branch, abattoir workstations seem to be associated with the highest prevalence of psittacosis. Complete eradication is difficult to achieve. Ventilation, cleaning, hand hygiene, and personal protective equipment are the most important protective measures to limit and control exposure to C. psittaci. Adequate information, communication, and health surveillance belong to the responsibilities of the occupational physician. Future challenges lay in the rigorous reporting of infections in both poultry and poultry workers and in the development of an avian and human vaccine.

Endemic and emerging chlamydial infections of animals and their zoonotic implications

The Chlamydiae are a diverse group of obligate intracellular Gram-negative bacteria that are known to infect a wide variety of host species and are responsible for a wide range of diseases in animals and man. Many of these organisms have been extensively characterized and their zoonotic implications recognized. Studies of human disease first provided evidence for the disease-causing potential of Chlamydia-related bacteria; however, there is now increasing evidence that a number of these organisms may also be the causative agents for a number of pathogenic conditions of livestock that had previously remained undiagnosed. The aim of this review is to draw together the evidence for the role of the newly emerging chlamydial infections in livestock disease, the current understanding of their roles in human disease and highlight the potential for zoonotic transmission.

Evaluation of bioaerosol sampling techniques for the detection of Chlamydophila psittaci in contaminated air

Chlamydophila (C.) psittaci, a category B bioterrorism agent, causes respiratory disease in birds and psittacosis or parrot fever in man. The disease spreads aerogenically and no vaccines are available for either birds or man. Highly sensitive C. psittaci bioaerosol monitoring methods are unavailable. We evaluated: (1) dry filtration for collecting C. psittaci from contaminated air using different samplers and membrane filters, (2) impingement into different liquid collection media by use of the AGI-30 impinger and the BioSampler and (3) impaction into newly designed C. psittaci media utilizing the MAS-100 aerosol impactor. For personal bioaerosol sampling, we recommend the use of a gelatin filter in combination with the IOM inhalable dust sampler at an airflow rate of 2L/min. This allowed the detection of 10 organisms of C. psittaci by both PCR and culture. For stationary bioaerosol monitoring, sampling 1000L of air in 10min with the MAS-100 impactor and ChlamyTrap 1 impaction medium was most efficient and made it possible to detect 1 and 10 C. psittaci organisms by PCR and culture, respectively. ChlamyTrap 1 in combination with the MAS-100 impactor might also be applicable for bioaerosol monitoring of viruses.

Isolation and characterization of Chlamydophila psittaci isolated from laying hens with cystic oviducts

The objective of this study was to isolate and identify a hypothetical Chlamydiaceae pathogen from laying hens with an oviduct cyst, and to characterize its potential causal relation with decreased egg production. Our clinical survey showed that cystic oviducts were prevalent at rates of 10% and 15.1% in breeder and commercial hen flocks, respectively. Chlamydial antigens were detected in 20 of 50 pharyngeal swabs (40%) and in 17 of 20 oviduct tissues (85%) using enzyme-linked immunosorbent assay (ELISA) antigen detection kits. The isolated pathogen was identified as Chlamydophila psittaci via complement fixation test, PCE-ELISA, and immunofluorescence assay. Avian influenza virus, Newcastle disease virus, and infectious bronchitis virus were excluded after oviduct tissues were inoculated onto the chorioallantoic membrane of embryonating eggs. The nucleotide sequence of the omp1 gene (accession no. EF202608) from the isolate was similar to that of C. psittaci avian type C (accession no. L25436). Typical cystic oviducts were observed in specific-pathogen-free hens inoculated intraperitoneally with the isolate. The high presence of chlamydial antigen is consistent with the cystic oviducts and poor egg production. We conclude that the isolated C psittaci is most likely associated with cystic oviducts in laying hens.

Evaluation of the prophylactic use of ovotransferrin against chlamydiosis in SPF turkeys

Chlamydophila (C.) psittaci infections are highly prevalent in turkeys and the economical and public health importance of these infections has been recognized since 1950. As there are no vaccines, antibiotic treatment (tetracylines, enrofloxacine) is often needed to allow marketing of poultry. In this study, we explored the use of ovotransferrin (ovoTF), a natural anti-microbial protein, in preventing an experimental C. psittaci infection in specific pathogen free (SPF) turkeys. Turkeys were treated with aerosolized ovoTF prior to the infection. Groups 1 and 2 received a single dose of 10 and 5 mg ovoTF per turkey, respectively. Group 3 received a daily dose of 5mg ovoTF per turkey during 12 days. Group 4 served as untreated, infected control group. Turkeys were aerosol infected using 10(6) TCID(50) of the virulent C. psittaci serovar/genotype D strain 92/1293. Birds were monitored (clinical signs, bacterial excretion) during 12 subsequent days before being necropsied. At necropsy, pathology and C. psittaci replication in various tissues was examined. A single dose of 10mg ovoTF and a repeated daily dose of 5mg ovoTF could not prevent the birds from becoming infected with C. psittaci, but they significantly reduced the outcome of the infection. A single dose of 5mg ovoTF had no influence on the outcome of the infection as compared to the non-treated infected controls. Our results demonstrate the anti-chlamydial effect of ovoTF in vivo and present a base for further research on practical applications of ovoTF on turkey farms.

Penetrating keratoplasty in a California Brown Pelican

Fresh homologous penetrating keratoplasty (PK) was performed on the left cornea of a young adult female California Brown Pelican (Pelecanus occidentalis) for the treatment of vision-threatening corneal scarring and granulation tissue. The procedure appeared to be highly successful based on short-term clinical follow-up and histopathology results. However, the patient died from unrelated causes before long-term follow-up could be obtained.

Exacerbation of Chlamydophila psittaci pathogenicity in turkeys superinfected by Escherichia coli

Both Chlamydophila psittaci and Escherichia coli infections are highly prevalent in Belgian turkeys and therefore they both might contribute to the respiratory disease complex observed in turkeys. C. psittaci can infect turkeys within the first week of age, even in the presence of maternal antibodies. However, the first C. psittaci outbreaks occur mostly at the age of 3 to 6 weeks, the period when also E. coli infections appear on the farms. Therefore, we examined in this study the pathogenicity of an E. coli superinfection on C. psittaci predisposed turkeys. Turkeys were infected with C. psittaci, E. coli or with C. psittaci followed by E. coli. Simulating the impact of an E. coli infection during the acute phase or the latent phase of a C. psittaci infection, turkeys received E. coli at 1 or 5 weeks post C. psittaci infection, respectively. E. coli superinfection during the acute phase of C. psittaci infection increased C. psittaci excretion and stimulated chlamydial replication in the respiratory tract resulting in exacerbated clinical disease. Interestingly, E. coli superinfection during the latent phase of C. psittaci infection induced chlamydial replication, leading to increased C. psittaci-specific antibody titres. In addition, chlamydial predisposition gave higher E. coli excretion compared with turkeys that had only been infected with E. coli. Overall, the present study clearly demonstrates the pathogenic interplay between C. psittaci and E. coli resulting in more severe respiratory disease.

Evaluation of a recombinant enzyme-linked immunosorbent assay for detecting Chlamydophila psittaci antibodies in turkey sera

Chlamydophila psittaci (formerly Chlamydia psittaci) is one of the major pathogens associated with turkey respiratory disease. Devastating outbreaks with high mortality rates, similar to those of 1950 to 1970 in the USA occasionally occur, but respiratory signs without or with low mortality mostly characterize outbreaks now a day. Accurate diagnostic methods should be made available. The present study examined the sensitivity and specificity of a recombinant ELISA (rMOMP ELISA) for detecting Cp. psittaci major outer membrane specific antibodies in turkey sera. Test results were compared to those of immunoblotting and of a competitive ELISA (Chlamydia-psittaci-AK-EIA, Röhm Pharma, Germany) and an indirect ELISA (LPS/LGP) detecting antibodies to the lipopolysaccharide/lipoglycoprotein complex. The rMOMP ELISA was most sensitive as determined on serial dilutions of positive control sera originating from experimentally infected SPF turkeys. The competitive ELISA gave false positives since three negative controls reacted positive. For conventional sera, the sensitivities of the competitive ELISA, immunoblotting and the indirect ELISA were found to be 99.4, 93.1 and 82.2%, respectively, as compared to the rMOMP ELISA (100%). The specificities of the rMOMP ELISA, immunoblotting and the indirect ELISA were found to be 100% while the specificity of the competitive ELISA was only 2.7%. The rMOMP ELISA was chosen to compare the prevalence of chlamydiosis in 2002 with the one from 1992. In 2002, 188 on 200 (94%) turkey sera reacted positive compared to 175 on 200 (87.5%) in 1992 and like 10 years ago all examined farms were seropositive at slaughter. Interestingly, Belgian as well as French farms were seropositive.

Use of a nested PCR-enzyme immunoassay with an internal control to detect Chlamydophila psittaci in turkeys

Background

Laboratory diagnosis of Chlamydophila psittaci, an important turkey respiratory pathogen, is difficult. To facilitate the diagnosis, a nested PCR-enzyme immunoassay (PCR-EIA) was developed to detect the Cp. psittaci outer membrane protein A (ompA) gene in pharyngeal swabs.

Methods

The fluorescein-biotin labelled PCR products were immobilized on streptavidin-coated microtiter plates and detected with anti-fluorescein peroxidase conjugate and a colorimetric substrate. An internal inhibition control was included to rule out the presence of inhibitors of DNA amplification. The diagnostic value of the ompA nested PCR-EIA in comparison to cell culture and a 16S-rRNA based nested PCR was assessed in pharyngeal turkey swabs from 10 different farms experiencing respiratory disease.

Results

The sensitivity of the nested PCR-EIA was established at 0.1 infection forming units (IFU). Specificity was 100%. The ompA nested PCR-EIA was more sensitive than the 16S-rRNA based nested PCR and isolation, revealing 105 out of 200 (52.5%) positives against 13 and 74 for the latter two tests, respectively. Twenty-nine (23.8%) out of 122 ompA PCR-EIA negatives showed the presence of inhibitors of DNA amplification, although 27 of them became positive after diluting (1/10) the specimens in PCR buffer or after phenol-chloroform extraction and subsequent ethanol precipitation.

Conclusion

The present study stresses the need for an internal control to confirm PCR true-negatives and demonstrates the high prevalence of chlamydiosis in Belgian turkeys and its potential zoonotic risk. The ompA nested PCR-EIA described here is a rapid, highly sensitive and specific diagnostic assay and will help to facilitate the diagnosis of Cp. psittaci infections in both poultry and man.

Influence of maternal antibodies on Chlamydophila psittaci-specific immune responses in turkeys elicited by naked DNA

Plasmid DNA (pcDNA1::MOMP D) expressing the major outer membrane protein (MOMP) of an avian Chlamydophila psittaci serovar D strain was tested for its ability to induce protective immunity against C. psittaci challenge in the presence of maternal antibodies. A combined parenteral (intramuscular injection) and mucosal route (DNA drops administered to the nares) of DNA inoculation was used. Following pcDNA1::MOMP vaccination, both T helper and B cell memory were primed. However, high maternal antibodies titres affected the induction of vaccine-specific antibody responses as assessed by MOMP-specific antibody levels in enzyme-linked immunosorbent assay (ELISA). Cell-mediated immunity was unaltered as demonstrated by the significantly heightened proliferative responses of peripheral blood lymphocytes (PBL) following vaccination. DNA vaccination could significantly reduce clinical symptoms, pharyngeal and cloacal excretion as well as Chlamydophila replication, even in the presence of maternal antibodies.

Dynamics of the development of Chlamydophila psittaci inclusions in epithelial and fibroblast host cells

The development of Chlamydophila psittaci (formerly Chlamydia psittaci, avian strains) inclusions in fibroblast L-929 and epithelial BGM cell lines was studied along the bacterial growth cycle using a BGM cell-adapted strain in the presence or absence of cycloheximide and cycloheximide + polyethylene glycol. Evolution of the inclusions was determined in terms of their number and size at 24, 30, 36, 48 and 54 h after infection. Significant differences in the chlamydial growth were found between both host cells, throughout the study. Higher numbers of inclusions (P < 0.05) were observed in L cells while larger inclusions (P < 0.01) were found in BGM cells. In both fibroblast and epithelial cells, inclusions showed a significant (P < 0.001) increase in size at the later times studied. Free extracellular chlamydial particles were noticed at 48 and 54 h post-infection (p.i.) in infected L cells, and at 54 h p.i. in BGM cells. Addition of cycloheximide or cycloheximide + polyethylene glycol had no significant effect on the number of inclusions or their size. The results suggest that host cell characteristics and innate compatibility between Chlamydophila strain and host cell are more important than host cell adaptation for the development of the microorganism.

Oxidative activity of turkey monocytes, following the inoculation with Chlamydia psittaci

Chemiluminescence (CL) was used to investigate the competence of turkey monocytes to mount a respiratory burst response upon interaction with Chlamydia psittaci. The oxidative activity of purified turkey monocytes, following inoculation with the avian C. psittaci serovar D strain 92/1293, was studied using luminol- and lucigenin-enhanced CL. Purified turkey monocytes were inoculated with C. psittaci at multiplicity of infection (MOI) of approximately 100, 10 and 1. In the presence of luminol, no detectable CL or only a weak CL response was obtained, and if present it increased with increasing MOI. Either sham inoculated monocytes, or monocyte-free control assays supplemented with C. psittaci, gave no detectable luminol-enhanced CL responses. In the lucigenin-enhanced assays, monocytes inoculated with C. psittaci demonstrated an immediate CL peak, the height of which was proportional to the MOI used. Following inoculations at a MOI 1, a faint second peak was observed, when applying high concentrations of lucigenin. Sham inoculated monocytes gave no detectable lucigenin-enhanced CL responses. However, in the presence of lucigenin, the addition of C psittaci to monocyte-free controls also resulted in an immediate CL peak, though no second peak was detected. This immediate lucigenin-dependent CL peak induced by C. psittaci was similar to the one observed in the presence of monocytes, and was not inhibited by superoxide dismutase. We demonstrated that this avian C. psittaci strain induces only a very weak respiratory burst response in turkey monocytes. In contrast, C. psittaci itself elicited an intense non-superoxide mediated lucigenin-dependent CL, indicating that in chlamydial research the detection of superoxide, using lucigenin, should be confirmed with a specific superoxide inhibitor.

High-level expression of Chlamydia psittaci major outer membrane protein in COS cells and in skeletal muscles of turkeys

The omp1 genes encoding the major outer membrane proteins (MOMPs) of avian Chlamydia psittaci serovar A and D strains were cloned and sequenced. The nucleotide sequences of the avian C. psittaci serovar A and D MOMP genes were found to be 98.9 and 87.8% identical, respectively, to that of the avian C. psittaci serovar A strain 6BC, 84.6 and 99.8% identical to that of the avian C. psittaci serovar D strain NJ1, 79.1 and 81.1% identical to that of the C. psittaci guinea pig inclusion conjunctivitis strain, 60.9 and 62.5% identical to that of the Chlamydia trachomatis L2 strain, and 57.5 and 60.4% identical to that of the Chlamydia pneumoniae IOL-207 strain. The serovar A or D MOMPs were cloned in the mammalian expression plasmid pcDNA1. When pcDNA1/MOMP A or pcDNA1/MOMP D was introduced into COS7 cells, a 40-kDa protein that was identical in size, antigenicity, and electrophoretic mobility to native MOMP was produced. Recombinant MOMP (rMOMP) was located in the cytoplasm of transfected COS7 cells as well as in the plasma membrane and was immunoaccessible. Intramuscular administration of pcDNA1/MOMP in specific-pathogen-free turkeys resulted in local expression of rMOMP in its native conformation, after which anti-MOMP antibodies appeared in the serum.

The prevalence of Chlamydia psittaci infections in Belgian commercial turkey poults

The prevalence of Chlamydia psittaci infections in Belgian commercial turkey poults was examined and a follow-up study of one Belgian turkey flock was performed. Sera were examined for the presence of anti-chlamydia antibodies by immunoblotting. Cloacal and conjunctival swab smears and lung impression smears were examined for the presence of chlamydial antigen using the IMAGEN Chlamydia immunofluorescence test. Anti-chlamydia antibodies were found in 90 of 100 sera collected at slaughter from turkeys raised during the summer of 1992. The following winter, 73 of 100 sera reacted positively. On all twenty farms examined during 1992, turkeys were positive for anti-chlamydial antibodies. During 1993, chlamydial antigen was detected in swabs from 20 of 40 slaughterhouse turkeys tested. Antigen was found more often in the cloaca than in the conjunctiva. Chlamydial antigen was detected in samples from each of the 4 farms examined. The follow-up study on a turkey farm, sampling the birds at weekly intervals from one week old until 12 weeks of age, revealed that chlamydial antigen and anti-chlamydial antibodies were present during the whole period. During 1994, chlamydial antigen was detected in 45 of 60 lungs from slaughterhouse turkeys from all of 6 farms. During 1995, chlamydial antigen was detected in 41 of 54 lungs of 6 week old commercial turkey poults. The results of the present study indicate that Chlamydia psittaci infections are highly prevalent amongst Belgian commercial turkey poults with apparently little seasonal or year-to-year variation and that turkeys can contract the infection at an early age.

Ultrastructural changes in avian Chlamydia psittaci serovar A-, B-, and D-infected Buffalo Green Monkey cells

In order to find an explanation for the observed differences in levels of pathogenicity in turkeys of Chlamydia psittaci 84/55 (avian serovar A), 89/1326 (avian serovar B), 92/1293 (avian serovar D), and the Texas Turkey strain (avian serovar D) (P.B. Wyrick, J. Choong, S.T. Knight, D. Goyeau, E.S. Stuart, and A.B. MacDonald, Immunol. Infect. Dis. 4:131-141, 1994), the reproductive cycles of organisms of the four strains were studied in Buffalo Green Monkey cells by transmission electron microscopy, immunoelectron microscopy, and flow cytometry. Organisms of strains most pathogenic in turkeys, namely, the serovar A strain and the 92/1293 serovar D strain, (i) replicated faster, since at 50 h postinoculation significantly larger inclusions with more numerous infectious organisms were observed than with the less pathogenic strains; (ii) were often found devoid of inclusion membranes scattered throughout the cytoplasms; and (iii) induced severe degenerative changes in Buffalo Green Monkey cells. By immunoelectron microscopy and flow cytometry, chlamydial antigens could not be detected in the plasma membranes of infected host cells. However, the presence of chlamydial antigens in inclusion membranes was demonstrated by immunoelectron microscopy.

Evaluation of five immunoassays for detection of Chlamydia psittaci in cloacal and conjunctival specimens from turkeys

Five commercially available immunoassays were evaluated for the detection of Chlamydia psittaci in cloacal and conjunctival swabs from industrially raised turkeys: IMAGEN (DAKO Diagnostics, Ely, Cambridgeshire, United Kingdom), Chlamydia CEL-VET IF (Cellabs, Brookvale, Australia), IDEIA (DAKO Diagnostics), CELISA (Cellabs), and CLEARVIEW (Unipath, Bedford, United Kingdom). Results were compared with isolation in Buffalo Green Monkey cells as a reference method. For the conjunctival samples, the sensitivities of the IMAGEN test, the Chlamydia CEL-VET IF test, the IDEIA, the CELISA, and the CLEARVIEW test were found to be 100, 66, 0, 0, and 0%, respectively, as compared to the reference test. Also for the conjunctival samples, the specificities of the IMAGEN test, the Chlamydia CEL-VET IF test, and the IDEIA were found to be 100, 11, and 92.8%, respectively. For the cloacal specimens, the sensitivities of the IMAGEN test, the Chlamydia CEL-VET IF test, the IDEIA, the CELISA, and the CLEARVIEW test were found to be 100, 93.3, 26.6, 0, and 53.3%, respectively. Also for the cloacal specimens, the specificities of the IMAGEN test, the Chlamydia CEL-VET IF test, the IDEIA, and the CLEARVIEW test were found to be 92, 12, 100, and 88%, respectively. The IMAGEN test was the most sensitive and specific direct chlamydia antigen detection test for cloacal and conjunctival samples from turkeys.