Genetic Diversity and Epizootiology ofChlamydophila psittaciPrevalent among the Captive and Feral Avian Species Based on VD2 Region ofompAGene

To study genetic diversity and occurrence of Chlamydophila psittaci, a total of 1,147 samples from 11 avian orders including 53 genera and 113 species of feral and captive birds were examined using ompA gene based nested PCR. Three types of chlamydiae: C. psittaci (94.12%), C. abortus (4.41%) and unknown Chlamydophila sp. (1.47%) were identified among 68 (5.93%) positive samples (Psittaciformes-59, Ciconiiformes-8 and Passeriformes-1). Based on nucleotide sequence variations in the VD2 region of ompA gene, all 64 detected C. psittaci strains were grouped into 4 genetic clusters. Clusters I, II, III and IV were detected from 57.35%, 19.12%, 10.29% and 7.35% samples respectively. A single strain of unknown Chlamydophila sp. was found phylogenetically intermediate between Chlamydophila species infecting avian and mammalian hosts. Among Psittaciformes, 28 out of 81 tested species including 10 species previously unreported were found to be chlamydiae positive. Chlamydiosis was detected among 8.97% sick and 48.39% dead birds as well 4.43% clinically normal birds. Therefore, it was observed that though various genetically diverse chlamydiae may cause avian chlamydiosis, only a few C. psittaci strains are highly prevalent and frequently associated with clinical/subclinical infections.

A new role of the complement system: C3 provides protection in a mouse model of lung infection with intracellular Chlamydia psittaci

The complement system modulates the intensity of innate and specific immunity. While it protects against infections by extracellular bacteria its role in infection with obligate intracellular bacteria, such as the avian and human pathogen Chlamydia (C.) psittaci, is still unknown. In the present study, knockout mice lacking C3 and thus all main complement effector functions were intranasally infected with C. psittaci strain DC15. Clinical parameters, lung histology, and cytokine levels were determined. A subset of infections was additionally performed with mice lacking C5 or C5a receptors. Complement activation occurred before symptoms of pneumonia appeared. Mice lacking C3 were ∼100 times more susceptible to the intracellular bacteria compared to wild-type mice, with all C3^−/− mice succumbing to infection after day 9. At a low infective dose, C3^−/− mice became severely ill after an even longer delay, the kinetics suggesting a so far unknown link of complement to the adaptive, protective immune response against chlamydiae. The lethal phenotype of C3^−/− mice is not based on differences in the anti-chlamydial IgG response (which is slightly delayed) as demonstrated by serum transfer experiments. In addition, during the first week of infection, the absence of C3 was associated with partial protection characterized by reduced weight loss, better clinical score and lower bacterial burden, which might be explained by a different mechanism. Lack of complement functions downstream of C5 had little effect. This study demonstrates for the first time a strong and complex influence of complement effector functions, downstream of C3 and upstream of C5, on the outcome of an infection with intracellular bacteria, such as C. psittaci.

The Chlamydia psittaci genome: a comparative analysis of intracellular pathogens

BACKGROUND

Chlamydiaceae are a family of obligate intracellular pathogens causing a wide range of diseases in animals and humans, and facing unique evolutionary constraints not encountered by free-living prokaryotes. To investigate genomic aspects of infection, virulence and host preference we have sequenced Chlamydia psittaci, the pathogenic agent of ornithosis.

RESULTS

A comparison of the genome of the avian Chlamydia psittaci isolate 6BC with the genomes of other chlamydial species, C. trachomatis, C. muridarum, C. pneumoniae, C. abortus, C. felis and C. caviae, revealed a high level of sequence conservation and synteny across taxa, with the major exception of the human pathogen C. trachomatis. Important differences manifest in the polymorphic membrane protein family specific for the Chlamydiae and in the highly variable chlamydial plasticity zone. We identified a number of psittaci-specific polymorphic membrane proteins of the G family that may be related to differences in host-range and/or virulence as compared to closely related Chlamydiaceae. We calculated non-synonymous to synonymous substitution rate ratios for pairs of orthologous genes to identify putative targets of adaptive evolution and predicted type III secreted effector proteins.

CONCLUSIONS

This study is the first detailed analysis of the Chlamydia psittaci genome sequence. It provides insights in the genome architecture of C. psittaci and proposes a number of novel candidate genes mostly of yet unknown function that may be important for pathogen-host interactions.

Diff-Quik cytologic recognition of Chlamydophila psittaci in orolabial lesions of Stevens-Johnson Syndrome

BACKGROUND

Chlamydophila psittaci causes psittacosis, an ornithosis acquired usually from infected birds. The disease is often focal and pneumonic but on rare instances can be protean and fatal. Diagnosis is by Chlamydophila serology, which may take as long as 21 days or more. The recovery of the organisms from mice, eggs or tissue culture inoculated with the patient's blood or sputum is tedious and dangerous for laboratory personnel. On occasion, C psittaci inclusion bodies have also been detected in infected cells by fluorescent antibody, Giemsa or Gimenez staining. This report describes heretofore not previously reported recognition of the causative organisms in Diff-Quik-stained clinical cytologic materials.

CASE

A 17-year-old man presented with fever and sore throat, associated with Steven-Johnson syndrome, of 6 days' duration. In the touch and scrape smears of the orolabial mucosal lesions, C psittaci inclusion bodies were recognizable in Diff-Quik-stained but not with Papanicolaou-stained smears and Gram stain. There were few to numerous organisms per macrophage, which were enlarged or bloated and usually collared by polymorphonuclear leukocytes. The diagnosis was supported by a therapeutic trial with doxycycline and confirmed by a positive third serological tests for C psittaci 3 weeks after discharge.

CONCLUSION

In a suspected or probable case of ornithosis, a rapid diagnosis of C psittaci inclusion bodies is possible in clinical cytology materials using Diff-Quik.

[Relationship between primary ocular adnexal mucosa-associated lymphoid tissue lymphoma and eye infection]

OBJECTIVE

To study the role of pathogenic microorganisms commonly associated with chronic eye disease, including Chlamydia psittaci, Chlamydia trachomatis, Chlamydia pneumoniae, herpes simplex virus (HSV) type 1 and type 2, and adenovirus type 8 and type 19, in the development of primary ocular adnexal mucosa-associated lymphoid tissue (MALT) lymphoma in Chinese patients.

METHODS

Sixty-eight archival cases of primary ocular adnexal lymphoproliferative lesions, including 38 cases of MALT lymphoma, 3 cases of non-MALT lymphoma and 27 cases of chronic inflammation, were enrolled into the study. DNA was extracted from the paraffin-embedded tissue samples. The presence of DNA of C. psittaci, C. trachomatis, C. pneumoniae, HSV type 1, HSV type 2, adenovirus type 8 and adenovirus type 19 were analyzed by multiplex touchdown enzyme time-release polymerase chain reaction (TETR-PCR).

RESULTS

All of the specimens yielded PCR products of over 100 base pairs and were thus suitable for TETR-PCR screening of infectious agents. The prevalence of DNA of C. psittaci, C. trachomatis and adenovirus type 19 were 0 in MALT lymphoma, non-MALT lymphoma and chronic inflammation. There were 2 cases positive for C. pneumoniae DNA, amongst the 38 cases of MALT lymphoma studied (5.3%, 2/38). HSV type 1, HSV type 2 and adenovirus type 8 DNA was found in each of the 3 patients with chronic inflammation.

CONCLUSION

The study indicates that C. psittaci, C. trachomatis, C. pneumoniae, HSV type 1, HSV type 2, adenovirus type 8 and adenovirus type 19 probably play little role in the pathogenesis of ocular adnexal MALT lymphoma in Chinese patients.

Development of an internally controlled real-time PCR assay for detection of Chlamydophila psittaci in the LightCycler 2.0 system

A real-time PCR assay with a DNA purification and inhibition control (internal control; IC) was developed to detect Chlamydophila psittaci DNA in human clinical samples. Novel C. psittaci-specific primers targeting the ompA gene were developed. The IC DNA contained the same primer-binding sites and had the same length and nucleotide content as the C. psittaci DNA amplicon, but had a shuffled probe-binding region. The lower limit of detection was 80 target copies/PCR, corresponding to 6,250 copies/mL in a clinical sample. Specificity was tested using reference strains of 30 bacterial species. No amplification was observed from any of these samples. Respiratory samples from eight patients were positive with this PCR. Six of these patients were confirmed as positive for C. psittaci with serological testing. Two patients had increasing antibody titres, but did not fulfil criteria proposed previously for serologically proven Chlamydia spp. infection. The real-time PCR described in this paper is a sensitive, specific and rapid method to detect C. psittaci DNA in human clinical respiratory samples.

Detection of Borrelia burgdorferi sensu lato and Chlamydophila psittaci in throat and cloacal swabs from birds migrating through Slovakia

We have screened 91 migratory birds representing 32 species during the autumn of 2003 for the presence of the zoonotic pathogens Borrelia and Chlamydophila. Using polymerase chain reaction (PCR), B. burgdorferi sensu stricto was detected in cloacal swabs and, in two causes, also in throat swabs in 8 individuals (8.7 %) representing 7 birds species; B. garinii and B. afzelii were not detected. C. psittaci was detected only in cloacal swabs; 6 birds (6.6 %) from four species were found to be positive. The PCR products were sequenced and the sequences were compared phylogenetically with the gene sequences of 14 Chlamydophila strains retrieved from nucleotide databases; although the sequenced DNA was only 110 bp long, all obtained sequences created a new cluster with sublines branching from a position close to the periphery of the genus. All tested samples appear distinct within the known species and were most similar to C. felis or C. abortis.

Meta-analyses of the association between Chlamydia psittaci and ocular adnexal lymphoma and the response of ocular adnexal lymphoma to antibiotics

BACKGROUND

There are conflicting reports regarding the association between Chlamydia psittaci (Cps) and ocular adnexal lymphoma (OAL) and the efficacy of antibiotics for OAL. In the current study, the authors attempted to clarify the association between Cps and OAL and the efficacy of antibiotics for OAL.

METHODS

Two meta-analyses were conducted. One focused on the association between Cps and OAL across geographic regions and among different studies. The other was a meta-analysis of the response of OAL to antibiotic treatment.

RESULTS

The authors identified 11 studies of Cps prevalence that included 458 cases of OAL from 10 different countries. Four studies regarding the efficacy of oral antibiotics to treat OAL were found. One hundred four of the 458 OAL specimens (23%) and 87 of the 346 mucosa-associated lymphoid tissue (MALT) lymphoma specimens (25%) were found to be positive for Cps. Ninety-four of the 104 Cps-positive OAL specimens (90%) came from 3 of the 11 studies. There was wide variation noted between geographic regions and even between studies from the same geographic region with regard to the rate of Cps positivity. The 4 studies concerning the efficacy of antibiotics for OAL were from Italy, Austria, Taiwan, and the U.S. and included 42 patients. Twenty patients (48%) achieved some response (complete response in 8 patients, partial response in 8 patients, and minimal response in 4 patients). Twenty patients also had stable disease, and 2 patients progressed during antibiotic therapy. Objective documentation of response (radiographs or clinical slit-lamp photographs) was available for only 3 of the 42 patients. Seven additional patients developed disease recurrence after their initial response or stable disease after antibiotic therapy; 6 of these cases of disease recurrence occurred during the first 12 months of follow-up.

CONCLUSIONS

The findings of the current study suggest a striking variability in the association between Cps and OAL across geographic regions and even between studies from the same geographic regions. The overall rate of Cps positivity in our meta-analysis (23%) was much lower than that reported in the original report. The current study findings also suggest that antibiotics have variable efficacy against OAL. Future prospective trials with standard objective response criteria and a longer follow-up period would be necessary to evaluate the role of antibiotics in the treatment of OAL further.

Genotyping of Chlamydophila psittaci in human samples

Chlamydophila (formerly Chlamydia) psittaci genotypes A, B, C, and a new genotype most similar to the 6BC type strain were found in 10 humans with psittacosis by outer membrane protein A gene sequencing. Genotypes B (n = 3) and C (n = 1) are endemic in nonpsittacine European birds. These birds may represent an important part of the zoonotic reservoir.

A pmp genes-based PCR as a valuable tool for the diagnosis of avian chlamydiosis

In a previous study we described the use of a new set of PCR primers (CpsiA/CpsiB) specific of the conserved pmp-family genes of Chlamydophila abortus as an efficient tool for the detection of these bacteria in ruminants including also preliminary results on avian strains. In this work, the use of this set of primers was extended to representative strains of the six major avian serovars (serovars A-F) and to field isolates of C. psittaci. For all the studied representative strains, using purified genomic DNA as a template, CpsiA/CpsiB primers allowed, as observed for C. abortus, a minimal 10-fold PCR signal increase compared to the one observed with ompA specific primers. In comparison to primers targeting the 16S-23S rRNA intergenic spacer, similar or increased sensitivity was observed depending on the strain. All the field isolates were amplified with CpsiA/CpsiB primers. On clinical samples, our primers are the best among those tested for detection of C. psittaci by simple conventional PCR. RFLP experiments performed using PCR fragments amplified with the CpsiA/CpsiB primers gave promising results demonstrating that these primers may provide an interesting tool for molecular typing when the bacterium cannot be grown from pathological samples.

An outbreak of psittacosis due to Chlamydophila psittaci genotype A in a veterinary teaching hospital

An outbreak of psittacosis in a veterinary teaching hospital was recognized in December 2004. Outbreak management was instituted to evaluate the extent of the outbreak and to determine the avian source. Real-time PCR, serologic testing and sequencing of the ompA gene of Chlamydophila psittaci were performed. Sputum samples from patients, throat-swab samples from exposed students and staff, and faecal specimens from parrots and pigeons were tested. In this outbreak, 34 % (10/29) of the tested individuals were infected. The clinical features of the infection ranged from none to sepsis with multi-organ failure requiring intensive-care-unit admission. C. psittaci genotype A was identified as the outbreak strain. Parrots, recently exposed to a group of cockatiels coming from outside the teaching facility, which were used in a practical class, appeared to be the source of the outbreak. One of the tested pigeons harboured an unrelated C. psittaci genotype B strain. The microbiological diagnosis by real-time PCR on clinical specimens allowed for rapid outbreak management; subsequent genotyping of the isolates identified the avian source. Recommendations are made to reduce the incidence and extent of future outbreaks.

A Comparative Study of Detecting Chlamydophila psittaci in Pet Birds Using Isolation in Embryonated Egg and Polymerase Chain Reaction

This study, for the first time in Turkey, investigated the existence of Chlamydophila psittaci and determined the prevalence of its disease, chlamydiosis, in pet birds. Polymerase chain reaction (PCR) was compared with other testing methods that have been typically used in the diagnosis of C. psittaci. Fecal specimens (n =96) of avian origin were tested by PCR and two identification methods, modified Gimenez staining (mGS) and direct fluorescein-conjugated monoclonal antibody staining (FA). The identification methods were implemented by staining the yolk sacs of embryonated chicken eggs inoculated at 6 days of age and harvested between 3 and 10 days after inoculation. Fecal specimens from pet birds were randomly collected from pet shops and homes. These specimens were then used to isolate C. psittaci and to detect its specific DNA. The inocula that were prepared from fecal specimens were then inoculated into yolks of 6-day-old embryonated chicken eggs. The preparations from egg yolk sacs were examined with mGS and direct FA after three blind passages. The PCR method was used to detect specific DNA in feces. In 96 fecal specimens, 33 (34.4%) were positive with PCR, 21 (21.9%) were positive with mGS, and 29 (30.2%) were positive with FA. Among 33 positive specimens with PCR, 28 specimens were positive with FA, and 20 specimens were positive with mGS. The sensitivity and specificity were 59% and 94% between FA and mGS, and 97% and 93% between FA and PCR, respectively.

Determination of the inhibitory concentration 50% (IC50) of four selected drugs (chlortetracycline, doxycycline, enrofloxacin and difloxacin) that reduce in vitro the multiplication of Chlamydophila psittaci

A total of 18 chlamydial isolates from various psittacine birds, one isolate from a domestic pigeon and one isolate from a Pekin duck were isolated in continuous Buffalo Green Monkey (BGM) kidney cell cultures. All 20 isolates were identified by nested multiplex polymerase chain reaction as Chlamydophila psittaci. These isolates were multiplied to high titres and subsequently tested for in vitro sensitivity against two tetracyclines (chlortetracycline and doxycycline) and two quinolones (enrofloxacin and difloxacin) at concentrations of 0.0, 0.25, 0.50, 1.00, and 10.00 microg/ml. Replication of chlamydia in BGM cell cultures is assayed on the basis of formation of intracytoplasmic inclusions that are visualized by Giménez staining. All isolates, although to variable degrees, are sensitive to all four drugs. The number of chlamydial inclusions decreases gradually over a broad range of increasing concentrations of the drugs. The variation in the number of inclusions between isolates is remarkably high for chlortetracycline less for doxycycline and minimal for both fluoroquinolones, the enrofloxacin and difloxacin. The decline in numbers of inclusions is highly dose-dependend and the observed reduction stretches over a wide range of drug dilutions. Therefore, it is proposed to calculate drug sensitivity values in terms of inhibitory concentration 50%, (IC5). Its calculation includes all tested drug dilutions instead of the hitherto more common minimal inhibitory concentration, MIC, which is based on results of serial dilution tests for cell-free growing bacteria. Using a logistic regression model for the calculation of the inhibitory concentration 50% of all 20 chlamydial isolates, the IC50 is 0.807 microg/ml for tetracycline, 0.497 microg/ml for doxycycline, 0.180 microg/ml for enrofloxacin and 0.168 microg/ml for difloxacin. Complete prevention of inclusion formation was already seen for enrofloxacin at a concentration of 1.0 microg/ml in 12 out of 20 and for difloxacin in 5 out of 20 isolates whereas more than 10 microg/mI chlortetracycline is needed in 15 out of 20 isolates and for doxycycline 9 out of 20 isolates yielded inclusions at 10 microg/ml.

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.

Rapidly Increasing Incidence of Ocular Non-Hodgkin Lymphoma

A recent report suggesting that ocular adnexal non-Hodgkin lymphoma (NHL) may be related to Chlamydia psittaci infection underscores the need for reliable epidemiologic data for this malignancy. We examined population-based incidence data from the Surveillance, Epidemiology, and End Results (SEER) Program. During 1992-2001 in the 12 SEER areas, ocular (i.e., eye and adnexa) NHL rates per 100,000 person-years for both sexes were highest among Asians/Pacific Islanders, lower in whites, and lower still in blacks. Incidence increased with advancing age and showed little difference by sex, in contrast to other (extranodal and nodal) NHLs, which occurred predominantly in males. From 1975-2001, there was a rapid and steady increase in incidence of ocular NHL, with annual increases of 6.2% and 6.5% among white males and females, respectively, with no evidence of peaking. By contrast, other NHLs showed evidence of peaking in recent years. The distinctive patterns of ocular NHL call for further studies to identify risk factors and mechanisms, including the potential role of C. psittaci or other infections.

Is there an association between ocular adnexal lymphoma and infection with Chlamydia psittaci?

Various subsets of extranodal marginal zone lymphomas of mucosa-associated lymphoid tissues (MALT lymphomas) have been associated with infectious organisms. Most notable of these is the association of gastric MALT lymphomas with Helicobacter pylori infection. In a recent publication Ferreri et al. [Ferreri AJ, Guidoboni M, Ponzoni M, De Conciliis C, Dell'Oro S, Fleischhauer K, et al. Evidence for an association between Chlamydia psittaci and ocular adnexal lymphomas. J Natl Cancer Inst 2004;96:586-94] reported the presence of C. psittaci DNA in 80% of 40 ocular adnexal lymphomas. Similar to the gastric MALT lymphoma data, a subset of these patients responded well to antibiotic treatment. We analyzed a set of ocular adnexal lymphomas and benign (non-neoplastic) lesions for evidence of C. psittaci DNA in patients from New York State. No evidence of C. psittaci DNA was seen in seven MALT-type ocular adnexal lymphomas, four non-MALT ocular lymphomas, one Langerhans histiocytosis, and five reactive lymphoproliferations. We eliminated several possible reasons that would cause our study to fail to find C. psittaci DNA, including the presence of PCR inhibitors, inadequate template DNA, and sequence diversity in the target region in C. psittaci. The positive data were based primarily on patients from Italy, while our study involved only patients living in the Northeastern United States. This would suggest possible geographic differences in the etiology of ocular adnexal lymphomas.

Chlamydophila psittaci in Fulmars, the Faroe Islands

Chlamydophila psittaci was detected in 10% of 431 fulmars examined from the Faroe Islands. Analysis of ompA showed a sequence almost identical to that of the type strain. The origin of C. psittaci outbreaks in fulmars is discussed. Despite a high level of exposure, the risk for transmission of C. psittaci to humans is low.

[Psittacosis outbreak in Granada, Spain]

BACKGROUND

Psittacosis can be transmitted to humans from infected birds, being the cause of atypical pneumonia. This work is aimed at determining the source of a psittacosis outbreak, the characteristics of the subjects exposed and describing the measures to control the outbreak.

METHODS

Descriptive study. Notification to the Epidemiological Monitoring System and Autonomic Agriculture authorities, taking the pertinent measures (inspection, sampling, disinfecting and precautionary quarantine of birds), closing the establishment. Case definition and epidemiological survey. Frequency analysis.

RESULTS

Seventeen (17) individuals (one of whom died) came into contact with suspicious animals (53% males/47% females), nine of whom (mean age: 30) showed symptoms (100% fever, flu-like symptoms 44.4%). A serology was performed for C. psitacci on 11 of the 17 subjects exposed (68.75%), two of whom (18.18%) tested positive. The presence of C. psittaci DNA was detected in the pulmonary tissue study conducted on the deceased individual. A total of 33% (3/9) of those showing symptoms were confirmed by diagnosis. The Autonomic Agriculture authorities placed 22 animal compounds under quarantine. A total of seven (10%) of the 70 samples taken (60: animal cloacas and 10 birds) revealed a positive antigen, the PCR nucleic acid test being positive in one there-of.

CONCLUSIONS

The exposure to diseased animals at the establishments involved caused the outbreak, the common source of contagion being of an occupational nature. The appropriate coordination/collaboration between the local Health and Agriculture authorities made it possible to prevent any further cases from arising.

An unusual cause of sepsis during pregnancy: recognizing infection with chlamydophila abortus

BACKGROUND

Chlamydophila abortus (formerly Chlamydia psittaci serovar 1) is a rare but severe cause of gestational septicemia, with particular problems in diagnosis and clinical management.

CASE

A 32-year-old woman in her fourth pregnancy (16th week of gestation) presented with progressive septicemia after extensive contact with abortive material from her goat flock. Treatment with levofloxacin could not prevent abortion. Multiorgan failure requiring catecholamines and artificial ventilation developed in the patient. After the agent was identified by polymerase chain reaction from acute-phase serum, macrolides were administered and yielded clinical improvement. The patient fully recovered. There were no sequelae in the subsequent 6 months.

CONCLUSION

Cp abortus must be considered in gestational septicemia after contact with ruminants. Polymerase chain reaction from acute-phase serum is a quick and easy way to establish the diagnosis. Macrolide antibiotics are still the treatment of choice.

[The case of 57-year-old patient with ornithosis]

The authors describe the case of ornithosis in the form of severe pleuropneumonia with breathing disorders. They emphasize that the proper diagnosis and consequently the treatment have been achieved by the detailed anamnesis and not by additional tests, as the immune reaction was found after full remission of pathological lesions.

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.