Evaluation of clinical characteristics and risk factors associated with Chlamydia psittaci infection based on metagenomic next-generation sequencing

INTRODUCTION

Psittacosis is a zoonosis caused by Chlamydia psittaci, the clinical manifestations of Psittacosis range from mild illness to fulminant severe pneumonia with multiple organ failure. This study aimed to evaluate the clinical characteristics of Chlamydia psittaci infection diagnosed based on metagenomic next-generation sequencing(mNGS), as well as the risk factors affecting the progress of Chlamydia psittaci infection, in order to improve the effect of therapeutics.

METHODS

We retrospectively analyzed the clinical data of patients infected with chlamydia psittaci in the First Affiliated Hospital of Nanchang University from January 2021 to December 2021. The patient's past medical history, clinical manifestations, laboratory examinations, chest CT results, treatment status, and prognosis data were collected. we also investigated both the pathogenic profile characteristics and the lower respiratory tract microbiota of patients with Chlamydia psittaci pneumonia using mNGS.

RESULTS

All cases of Chlamydia psittaci in our research have been confirmed by mNGS. Among 46 cases of Chlamydia psittaci pneumonia, Poultry exposure was reported in 35 cases. In severe cases of Chlamydia psittaci pneumonia, Neutrophils, Procalcitonin (PCT), Lactate Dehydrogenase (LDH), Hydroxybutyrate Dehydrogenase (HBDH), Creatine Kinase Isoenzymes-B (CK-MB) and D-Dimer levels were remarkably higher than that of non-severe cases, except for lymphocytes (all P < 0.05). Chest CT scans showed Bilateral (77.8%), multiple lobar lungs (85.2%), pleural effusions (44.4%) involvement in those suffering from severe Chlamydia psittaci pneumonia, whereas its incidence was 0%, 21.1% and 10.5% in non-severe patients, respectively (P < 0.05). Multivariate analysis revealed that higher lymphocyte concentrations (OR 0.836, 95% CI 0.714-0.962, P = 0.041) were the only protective factor for survival. mNGS results indicated that 41.3% of patients (19/46) had suspected coinfections with a coinfection rate of 84.2% (16/19) in the severe group, much higher than that in the non severe group (p < 0.05). No significantly different profiles of lower respiratory tract microbiota diversity were found between non severe group and severe group.

CONCLUSION

A history of poultry exposure in patients can serve as an important basis for diagnosing Chlamydia psittaci pneumonia, and patients with severe Chlamydia psittaci pneumonia are more likely to develop elevated inflammatory biomarkers as well as elevated cardiac markers. Higher lymphocyte concentrations are protective factors associated with severe C. psittaci pneumonia. The higher proportion of patients with coinfections in our study supports the use of mNGS for comprehensive early detection of respiratory infections in patients with C. psittaci pneumonia.

SNP-based high-resolution typing of Chlamydia psittaci from humans and wild birds in Sweden: circulation of the Mat116 genotype reveals the transmission mode to humans

The incidence of Chlamydia psittaci respiratory tract infections in humans has increased in Sweden in recent years. This study aimed to identify the transmission route by genotyping C. psittaci from infected humans and birds. 42 human C. psittaci samples and 5 samples from C. psittaci-infected birds were collected. Genotyping was performed using ompA sequencing, Multi-locus sequence typing, and/or SNP-based high-resolution melting-PCR. Epidemiological data was also collected, and a phylogenetic analysis was conducted. Analysis of ompA provided limited resolution, while the SNP-based PCR analysis successfully detected the Mat116 genotype in 3/5 passerine birds and in 26/29 human cases, indicating a high prevalence of this genotype in the human population. These cases were associated with contact with wild birds, mainly through bird feeding during winter or other outdoor exposure. Human cases caused by other genotypes (psittacine and pigeon) were less common and were linked to exposure to caged birds or pigeons. The SNP-genotype Mat116 is rare, but predominated in this study. The use of SNP-based PCR provided a better understanding of the C. psittaci transmission from birds to humans compared to ompA analysis. In Sweden, human psittacosis appears mainly to be transmitted from garden birds during bird feeding in the winter season.

Engineering of the LAMP-CRISPR/Cas12b platform for Chlamydia psittaci detection

Introduction. Chlamydia psittaci (C. psittaci) is a zoonotic infection, that causes psittacosis (parrot fever) in humans, leading to severe clinical manifestations, including severe pneumonia, adult respiratory distress syndrome, and, in rare cases, death.Gap Statement. Rapid, sensitive and specific detection of C. psittaci facilitates timely diagnosis and treatment of patients.Aim. This study aimed to engineer the LAMP-CRISPR/Cas12b platform for C. psittaci detection.Methodology. The loop-mediated isothermal amplification (LAMP) technique and clustered regularly interspaced short palindromic repeats-CRISPR associated protein 12b (CRISPR-Cas12b) assay were combined to establish two-step and one-tube LAMP-CRISPR/Cas12b reaction systems, respectively, for rapidly detecting C. psittaci.Results. The two-step and one-tube LAMP-CRISPR/Cas12b assay could complete detection within 1 h. No cross-reactivity was observed from non-C. psittaci templates with specific LAMP amplification primers and single-guide RNA (sgRNA) targeting the highly conserved short fragment CPSIT_0429 gene of C. psittaci. The detection limits of the two-step and one-tube LAMP-CRISPR/Cas12b reaction were 102 aM and 103 aM, respectively. The results were consistent with qPCR for nucleic acid detection in 160 clinical samples, including 80 suspected C. psittaci samples, kept in the laboratory.Conclusions. The LAMP-CRISPR/Cas12b assay developed in this study provides a sensitive and specific method for rapidly detecting C. psittaci and offers technical support for its rapid diagnosis.

TLR2 mediates autophagy through ERK signaling pathway in Chlamydia psittaci CPSIT_p7 protein-stimulated RAW264.7 cells

Chlamydia psittaci is a zoonotic pathogen found in birds and humans. Macrophages, major components of the innate immune system, can resist chlamydial infections and trigger adaptive immune responses. However, the molecular mechanisms underlying the action of macrophages against C. psittaci infection are not well understood. This study investigated the roles and mechanisms of plasmid-encoded protein CPSIT_p7 of C. psittaci in regulating autophagy in RAW264.7 cells. The results demonstrated that stimulation of RAW264.7 with C. psittaci plasmid protein CPSIT_p7 induced the expressions of the autophagy signaling primary regulators LC3 and Beclin1, which could also significantly induce the phosphorylation levels of ERK, JNK, p38, and Akt. Next, siRNA knockdown of TLR2 resulted in significant downregulation of CPSIT_p7-triggered autophagy in RAW264.7 cells. Moreover, the extracellular regulated protein kinase (ERK) inhibitor PD98059 markedly reduced autophagy in CPSIT_p7-stimulated macrophages. In summary, these results indicated that TLR2 plays an essential role in the induction of autophagy through the ERK signaling pathway in CPSIT_p7-stimulated RAW264.7 cells.

Whole genome sequencing characteristics of Chlamydia psittaci caprine AMK-16 strain, a promising killed whole cell veterinary vaccine candidate against chlamydia infection

Chlamydia psittaci is a primary zoonotic pathogen with a broad host range causing severe respiratory and reproductive system infection in animals and humans. To reduce the global burden of C. psittaci-associated diseases on animal welfare and health and to control the pathogen spread in husbandry, effective vaccines based on promising vaccine candidate(s) are required. Recently, the caprine C. psittaci AMK-16 strain (AMK-16) demonstrated a high level of protection (up to 80-100%) in outbred mice and pregnant rabbits immunized with these formaldehyde-inactivated bacteria against experimental chlamydial wild-type infection. This study investigated the molecular characteristics of AMK-16 by whole-genome sequencing followed by molecular typing, phylogenetic analysis and detection of main immunodominant protein(s) eliciting the immune response in mouse model. Similarly to other C. psittaci, AMK-16 harbored an extrachromosomal plasmid. The whole-genome phylogenetic analysis proved that AMK-16 strain belonging to ST28 clustered with only C. psittaci but not with Chlamydia abortus strains. However, AMK-16 possessed the insert which resulted from the recombination event as the additional single chromosome region of a 23,100 bp size with higher homology to C. abortus (98.38-99.94%) rather than to C. psittaci (92.06-92.55%). At least six of 16 CDSs were absent in AMK-16 plasticity zone and 41 CDSs in other loci compared with the reference C. psittaci 6BC strain. Two SNPs identified in the AMK-16 ompA sequence resulted in MOMP polymorphism followed by the formation of a novel genotype/subtype including three other C. psittaci strains else. AMK-16 MOMP provided marked specific cellular and humoral immune response in 100% of mice immunized with the inactivated AMK-16 bacteria. Both DnaK and GrpE encoded by the recombination region genes were less immunoreactive, inducing only a negligible T-cell murine immune response, while homologous antibodies could be detected in 50% and 30% of immunized mice, respectively. Thus, AMK-16 could be a promising vaccine candidate for the development of a killed whole cell vaccine against chlamydiosis in livestock.

Case Report: Metagenomic next-generation sequencing applied in diagnosing psittacosis caused by Chlamydia psittaci infection

Background

Chlamydia psittaci is the causative agent of psittacosis in humans, while its rapid identification is hampered due to the lack of specificity of laboratory testing methods.

Case presentation

This study reports four cases of C. psittaci infection after contact with a domestic parrot, all belonging to the same family. Common manifestations like fever, cough, headache, nausea, and hypodynamia appeared in the patients. Metagenomic next-generation sequencing (mNGS) aided the etiological diagnosis of psittacosis, revealing 58318 and 7 sequence reads corresponding to C. psittaci in two cases. The detected C. psittaci was typed as ST100001 in the Multilocus-sequence typing (MLST) system, a novel strain initially reported. Based on the results of pathogenic identification by mNGS, the four patients were individually, treated with different antibiotics, and discharged with favorable outcomes.

Conclusion

In diagnosing psittacosis caused by a rare C. psittaci agent, mNGS provides rapid etiological identification, contributing to targeted antibiotic therapy and favorable outcomes. This study also reminds clinicians to raise awareness of psittacosis when encountering family members with a fever of unknown origin.

Clinical features and outcome of eight patients with Chlamydia psittaci pneumonia diagnosed by targeted next generation sequencing

INTRODUCTION

The clinical symptoms of Chlamydia psittaci pneumonia are still poorly understood. This study was designed to summarize the clinical features and outcome of eight C. psittaci pneumonia patients diagnosed by targeted next generation sequencing (tNGS).

METHODS

We included eight C. psittaci pneumonia patients admitted to our hospital from January 2021 to July 2022. The tNGS was performed to the samples collected from bronchoalveolar lavage fluid of each patient. Their clinical data were analysed, including baseline features, clinical symptoms, chest radiographic findings and laboratory examinations.

RESULTS

The tNGS sequence number for C. psittaci was in a range of 10 to 1722. The radiographic characteristics were mainly featured by patchy consolidation shadows, ground-glass density shadows, air bronchogram and slight pleural effusion. Within 1-3 days after hospitalization, most patients showed increased neutrophil ratio, C-reactive protein and erythrocyte sedimentation rate, and decreased lymphocyte count, total protein, albumin and prealbumin. Some patients showed increased glutamic-pyruvic transaminase, glutamic-oxaloacetic transaminase and lactate dehydrogenase levels. Three critically ill patients showed increased creatine kinase, creatine kinase isoenzyme and high-sensitivity troponin T (hs-TnT) levels.

CONCLUSIONS

A poultry or bird contact history, typical flu-like symptoms, patchy consolidation, ground-glass density shadow and air bronchogram may contribute to the diagnosis and treatment of C. psittaci pneumonia. Increase in creatine kinase, creatine kinase isoenzyme and hs-TnT may indicate a severe condition. Moxifloxacin and minocycline were effective in the management of C. psittaci pneumonia.

Application of environmental sampling to investigate a case of avian chlamydiosis in a pet store and breeding facility leading to mass bird exposures

Chlamydia psittaci is a bacterium that causes chlamydiosis in birds and can cause zoonotic psittacosis in people. In November 2017, we received notification of a suspected case of avian chlamydiosis in a captive cockatiel (Nymphicus hollandicus) that was sold by an online pet bird retail and breeding facility in Washington State. We describe the investigation with emphasis on how environmental sampling was used to guide veterinary and public health interventions. Bird samples were collected either from pooled droppings, pooled plumage or individual nasal and choanal swabs. Environmental samples were obtained by swabbing cleaning mops, tables and cage structures. All samples were tested by polymerase chain reaction and positive samples underwent genotyping. Approximately 1000 birds representing four taxonomic orders were kept within an open-space warehouse. Eight of 14 environmental samples and one of two pooled faecal samples were positive for Chlamydia spp. The contaminating strain of Chlamydia spp. was identified as genotype A. The facility was closed for environmental disinfection, and all psittacines were treated with oral doxycycline for 45 days. Ten of 10 environmental and two of two pooled faecal samples were negative for C. psittaci 11 months after the completion of environmental disinfection and antimicrobial treatment. This investigation highlights the importance of preventing and mitigating pathogen incursion in an online pet retail and breeding facility. Environmental sampling is valuable to guide animal and public health interventions for control of C. psittaci, particularly when large numbers of birds are exposed to the pathogen.

Case Report: Clinical analysis of a cluster outbreak of chlamydia psittaci pneumonia

Objective

To explore the clinical characteristics and prognosis of clustered cases of psittacosis pneumonia.

Method

We retrospectively analyzed the clinical data of a cluster outbreak of psittacosis pneumonia. The analysis included epidemiological data, clinical symptoms, laboratory results, and prognosis. The diagnosis was made using mNGS and nested PCR technology.

Result

Of the four cases, two had direct contact with diseased poultry while the other two did not. All cases presented with more than 39.5 °C fever and chills. Additionally, significant increases in C-reactive protein, ferritin, creatine kinase, and lactate dehydrogenase were observed in all cases, while absolute lymphocyte count decreased. Case 2 also had increased calcitonin levels. Acute respiratory failure occurred during the treatment of case 1 and case 2, leading to tracheal intubation and ventilator-assisted ventilation. Unfortunately, case 2 passed away due to sepsis and multiple organ dysfunction, while the other cases had a positive prognosis.

Conclusion

mNGS facilitated the early diagnosis of psittacosis pneumonia. It is important to note that there is still a substantial risk of human-to-human transmission in psittacosis pneumonia. Absolute lymphocyte count and calcitonin levels can predict the severity and prognosis of the disease.

Whole-genome sequencing of Chlamydia psittaci from Australasian avian hosts: A genomics approach to a pathogen that still ruffles feathers

Chlamydia psittaci is a globally distributed veterinary pathogen with zoonotic potential. Although C. psittaci infections have been reported in various hosts, isolation and culture of Chlamydia is challenging, hampering efforts to produce contemporary global C. psittaci genomes. This is particularly evident in the lack of avian C. psittaci genomes from Australia and New Zealand. In this study, we used culture-independent probe-based whole-genome sequencing to expand the global C. psittaci genome catalogue. Here, we provide new C. psittaci genomes from two pigeons, six psittacines, and novel hosts such as the Australian bustard (Ardeotis australis) and sooty shearwater (Ardenna grisea) from Australia and New Zealand. We also evaluated C. psittaci genetic diversity using multilocus sequence typing (MLST) and major outer membrane protein (ompA) genotyping on additional C. psittaci-positive samples from various captive avian hosts and field isolates from Australasia. We showed that the first C. psittaci genomes sequenced from New Zealand parrots and pigeons belong to the clonal sequence type (ST)24 and diverse 'pigeon-type' ST27 clade, respectively. Australian parrot-derived strains also clustered in the ST24 group, whereas the novel ST332 strain from the Australian bustard clustered in a genetically diverse clade of strains from a fulmar, parrot, and livestock. MLST and ompA genotyping revealed ST24/ompA genotype A in wild and captive parrots and a sooty shearwater, whilst 'pigeon-types' (ST27/35 and ompA genotypes B/E) were found in pigeons and other atypical hosts, such as captive parrots, a little blue penguin/Kororā (Eudyptula minor) and a zebra finch (Taeniopygia guttata castanotis) from Australia and New Zealand. This study provides new insights into the global phylogenomic diversity of C. psittaci and further demonstrates the multi-host generalist capacity of this pathogen.

Prevalence and Risk Factors of Avian Chlamydiosis Detected by Polymerase Chain Reaction in Psittacine Birds in Thailand

This study surveyed avian chlamydiosis, with the aim to estimate the prevalence and potential risk factors associated with Chlamydia psittaci infection in psittacine birds kept as domestic pets in Thailand. Oropharyngeal swabs were collected from 120 psittacine birds that were randomly selected from hospitals in the central (Bangkok) and northeastern regions (Khon Kaen) of Thailand between 2019 and 2021. The oropharyngeal swabs were subject to polymerase chain reaction testing to detect the C psittaci ompA gene. The prevalence of C psittaci was 2.5% (3/ 120, 95% confidence interval = 0.3-5.3). Of the 3 positive birds, 1 was a Forpus parrot (Forpus species)(CP43TH) and 1 was an African grey parrot (Psittacus erithacus)(CP49TH) from Bangkok; both were juvenile birds with clinical signs of disease. The third positive bird (CP12TH) was a subclinical adult sun conure (Aratinga solstitialis) from Khon Kaen. Two sequences of samples that were previously identified in human psittacosis cases (accession numbers MK032053.1 and HM450409.1) were also examined. Since there was a low number of infected birds, potential associations between C psittaci infection and various environmental variables (eg, cage cleaning, synanthropic birds, quarantine of new birds, and overcrowding) were assessed by Fisher exact tests. This study provides estimates of the prevalence and potential risk factors associated with C psittaci infection in psittacine birds from central (Bangkok) and the northeastern regions (Khon Kaen) of Thailand. The detection of C psittaci in captive psittacine birds demonstrates that there is a possibility for bird-to-bird transmission as well as some zoonotic potential for the human caretakers of these birds. Furthermore, larger-scale studies should be conducted to confirm these findings.

Clinical and chest computed tomography features associated with severe Chlamydia psittaci pneumonia diagnosed by metagenomic next-generation sequencing: A multicenter, retrospective, observational study

Chlamydia psittaci pneumonia is a rare disease with varying clinical presentations. Here, we aimed to investigate the clinical and chest computed tomography (CT) features of severe psittacosis pneumonia. Clinical data of 35 patients diagnosed with psittacosis pneumonia were retrospectively analyzed using metagenomic next-generation sequencing. The patients were classified into severe (n = 20) and non-severe (n = 15) groups. The median age of patients was 54 years, and 27 patients (77.1%) had a definite history of bird contact. Severe patients had more underlying comorbidities and were more prone to dyspnea and consciousness disorders than non-severe patients. The neutrophil count and D-dimer, lactate dehydrogenase, interleukin (IL)-2, IL-6, and IL-10 levels were higher, whereas the lymphocyte, CD3 + T cell, and CD4 + T cell counts, CD4+/CD8 + T cell ratio, and albumin level were substantially lower in severe patients than in non-severe patients. Chest CT findings of severe patients revealed large areas of pulmonary consolidation, and ground-glass opacities were observed in some patients, with a higher risk of involving multiple lobes of the lungs and pleural effusion. One patient died of multiple organ failure, whereas the condition of the other 34 patients improved, and they were discharged from the hospital. Patients with severe psittacosis pneumonia often have underlying comorbidities and are prone to developing dyspnea, consciousness disorder, and lesions in both lungs. Serum D-dimer, IL-2, IL-6, and IL-10 levels and lymphocyte, CD3 + T cell, and CD4 + T cell counts are associated with disease severity.

A Chlamydia psittaci Outbreak in Psittacine Birds in Sardinia, Italy

Chlamydia psittaci is an intracellular bacterium belonging to the Chlamydiaceae family. It is the ethiologic agent of psittacosis, an occupational zoonotic disease that mainly concerns people who work in close contact with birds that represent the main infection route for human transmission. In Italy, information about this disease is lacking. This study is the first case of avian chlamydiosis reported from a pet shop in Sardinia, Italy. Chlamydia psittaci detected in psittacine birds by molecular analysis, direct immunofluorescence test together with anatomo-pathological observed lesions, highlighted the importance of focusing the attention over this underestimated zoonosis in a "One Health" prospective.

Clinical diagnosis and etiology of patients with Chlamydia psittaci pneumonia based on metagenomic next-generation sequencing

The incidence of severe Chlamydia psittaci (C. psittaci) pneumonia and coinfections is increasing. Early detection of this condition is needed to prevent negative outcomes, along with detailed descriptions of its associated clinical characteristics. Our study contributes by undertaking etiological analysis of patients with C. psittaci pneumonia based on metagenomic next-generation sequencing (mNGS). A retrospective analysis of 30 patients with C. psittaci pneumonia was undertaken and confirmed by mNGS or polymerase chain reaction (PCR). Clinical manifestations of the severe and non-severe C. psittaci pneumonia groups were compared for clinical reference. Etiological analyses were also performed to comprehensively understand pathogeny and coinfection with other respiratory pathogens in C. psittaci patients. The absolute value of lymphocytes (LYM) in the severe group was lower than in the non-severe group. At the same time, neutrophil-to-lymphocyte ratio (NLR), procalcitonin (PCT), alanine aminotransferase (ALT), D-II polymer, brain natriuretic peptide (BNP), myoglobin (MYO), and cardiac troponin I (cTnI) were significantly higher (P < 0.05) in the severe group. mNGS has a broader pathogen spectrum and can more sensitively detect C. psittaci and other low-abundance pathogens with a higher positive detection rate (100%, 13/13 vs. 46%, 6/13, P <0.05) than conventional culture methods. mNGS detected the following dominant species associated with C. psittaci in patients: bacteria (53.2%, 39% gram-positive, 61% gram-negative), fungi (12.9%), and viruses (33.9%). A total of 73.3% (11/15) of patients had suspected coinfections, with a coinfection rate of 91.7% (11/12) in the severe group. No coinfection or death occurred in the non-severe group. Prognosis in the severe group was poor, with a mortality rate of 27.3% (3/11) for patients with coinfection. Eight of 11 patients with coinfections (72.7%) recovered. In conclusion, the clinical symptoms of severe C. psittaci pneumonia manifested as abnormal inflammatory indicators, impaired liver function, myocardial injury, coagulation, and relatively low immune responses. The higher proportion of patients with coinfections in our study supports the use of mNGS for comprehensive early detection of respiratory infections in patients with C. psittaci pneumonia. Simultaneous early identification of coinfections would further improve the clinical treatment of these patients.

Chlamydia psittaci plasmid-encoded CPSIT_P7 induces macrophage polarization to enhance the antibacterial response through TLR4-mediated MAPK and NF-κB pathways

Although the protective effects of Chlamydia psittaci plasmid-encoded protein CPSIT_P7 as vaccine antigens to against chlamydial infection have been confirmed in our previous study, the function and mechanism of CPSIT_P7 inducing innate immunity in the antibacterial response remain unknown. Here, we found that plasmid protein CPSIT_P7 could induce M1 macrophage polarization upregulating the genes of the surface molecule CD86, proinflammatory cytokines (TNF-α, IL-6, and IL-1β), and antibacterial effector NO synthase 2 (iNOS). During M1 macrophage polarization, macrophages acquire phagocytic and microbicidal competence, which promotes the host antibacterial response. As we observed that CPSIT_P7-induced M1 macrophages could partially reduce the infected mice pulmonary Chlamydia psittaci load. Furthermore, CPSIT_P7 induced M1 macrophage polarization through the TLR4-mediated MAPK and NF-κB pathways. Collectively, our results highlight the effect of CPSIT_P7 on macrophage polarization and provide new insights into new prevention and treatment strategies for chlamydial infection.

Atypical pneumonia caused by Chlamydia psittaci during the COVID-19 pandemic

OBJECTIVES

Here, we retrospectively described the diagnosis and treatment of 32 cases diagnosed with Chlamydia psittaci pneumonia during the COVID-19 pandemic.

METHODS

Clinical information was collected from all the patients. Reverse transcription-PCR and ELISAs were conducted for the detection of COVID-19 using nasal swabs and bronchoalveolar lavage fluid (BALF) samples. Metagenomic next-generation sequencing (mNGS) was performed for the identification of causative pathogens using BALF, peripheral blood and sputum samples. End-point PCR was performed to confirm the mNGS results.

RESULTS

All 32 patients showed atypical pneumonia and had infection-like symptoms that were similar to COVID-19. Results of reverse transcription-PCR and ELISAs ruled out COVID-19 infection. mNGS identified C. psittaci as the suspected pathogen in these patients within 48 hours, which was validated by PCR, except for three blood samples. The sequence reads that covered fragments of C. psittaci genome were detected more often in BALF than in sputum or blood samples. All patients received doxycycline-based treatment regimens and showed favorable outcomes.

CONCLUSION

This retrospective study, with the highest number of C. psittaci pneumonia enrolled cases in China so far, suggests that human psittacosis may be underdiagnosed and misdiagnosed clinically, especially in the midst of the COVID-19 pandemic.

Application of Metagenomic Next-Generation Sequencing in the Diagnosis of Pneumonia Caused by Chlamydia psittaci

Psittacosis is an uncommon disease which mainly presents as community-acquired pneumonia (CAP). We aim to apply metagenomic next-generation sequencing (mNGS) as a promising tool in the diagnosis of psittacosis pneumonia and to describe its clinical spectrum to provide physicians with a better understanding and recognition of this disease. Thirteen cases of psittacosis pneumonia were diagnosed by using mNGS. A retrospective analysis of the data on clinical manifestations, laboratory data, computed tomography (CT) images, new diagnosis tools, treatments, and outcomes was summarized. These patients had common symptoms of fever and weakness; some had poor appetite, cough, myalgia, and headache. Ten patients developed acute respiratory distress syndrome (ARDS), among which six patients were severe pneumonia cases and needed ventilator therapy. Most patients got psittacosis pneumonia during the cold season. Ten cases were sporadic, but three were family clustering. All of the 13 patients were traced to an exposure history to birds, cat, or poultry, among which 2 only touched the innards of killed poultry before cooking, which may be an atypical exposure history not been reported before, to our knowledge. Most patients had various degrees of liver dysfunction. Air-space consolidations, along with ground-glass opacities and reticular shadows, were detected on chest CT scan. mNGS takes 48 to 72 h to provide results and helps to diagnose psittacosis. After being diagnosed by mNGS, with effective medicines, all patients finally had complete recoveries. The use of mNGS can improve the diagnostic rate of psittacosis pneumonia and shorten the course of disease control. IMPORTANCE Psittacosis pneumonia is easily underdiagnosed and misdiagnosed. In this study, we use mNGS in the diagnosis of psittacosis pneumonia. We found this disease is prone in the cold season, and touching the innards of killed poultry during cooking may be an atypical exposure history which has not been reported before to our knowledge. There are sporadic cases and family outbreak cases as well. Except for typical symptoms of fever and weakness, headache may be the main and only symptom in some patients. The rate of severe pneumonia is high among inpatients with psittacosis pneumonia, and the incidence of hepatic involvements is also high. Psittacosis pneumonia can be cured if the diagnosis is accurate and in time, even if it is severe pneumonia on admission. Some problems worthy of our attention about psittacosis pneumonia were put forward, such as its sick season, special exposure history, the rate of severe disease, and the high cure rate. mNGS can quickly and objectively detect more rare pathogenic microorganisms in clinical specimens without the need for specific amplification and has an advantage in the diagnosis of rare pathogenic bacteria in difficult cases such as psittacosis pneumonia. The use of mNGS can improve the accuracy and reduce the delay in the diagnosis of psittacosis, which shortens the course of disease control.

Clinical, radiological and pathological characteristics of moderate to fulminant psittacosis pneumonia

Background

Psittacosis pneumonia is a community-acquired pneumonia caused by Chlamydia psittaci. It is usually under-diagnosed due to its atypical clinical presentation and lack of routine laboratory tests.

Methods

To better understand the clinical features, 52 patients diagnosed with psittacosis pneumonia by metagenomic next-generation sequencing (mNGS) were enrolled in this study. The clinical, radiological and pathological characteristics were retrospectively analyzed.

Results

The onset of psittacosis pneumonia in this study occurred all year round, with a peak from December to January. Most of the patients were 51–80 years old. About 65.38% of patients had a history of exposure to poultry or parrots. Abnormalities of multiple clinical signals were detected in these patients. Elevated levels of neutrophil ratio, C-reactive protein, erythrocyte sedimentation rate, and procalcitonin were detected in most patients. Radiological evidence revealed air-space consolidation or ground-glass opacities in lungs of all patients, which is the typical feature of psittacosis pneumonia. In addition, hyperemia, swelling of bronchial mucosa, and bronchial patency were detected by bronchoscopy in all patients, and bronchial sub-mucosal edema, inflammatory cells infiltration and alveolar epithelial hyperplasia were identified in the bronchial mucosa and alveolar tissue. Beta-lactam antibiotics were administered for empirical treatment before mNGS in 17 patients but showed no improvement. The treatment was switched to doxycycline or moxifloxacin immediately since psittacosis pneumonia were suspected and confirmed by mNGS detection (within 48 hours). After receiving adjustment of treatment, 94.23% (49/52) of patients were cured successfully.

Conclusions

In conclusion, mNGS may be a promising approach for clinical diagnosis of psittacosis. For patients with a history of exposure to birds, hyperpyrexia, nonproductive cough, multiple elevated inflammatory markers, and air-space consolidation in lung, psittacosis pneumonia should be considered, especially when beta-lactam antibiotics showed limited efficacy.

Clinical characteristics of 14 cases of severe Chlamydia psittaci pneumonia diagnosed by metagenomic next-generation sequencing: A case series

INTRODUCTION

The objective of this study was to explore the clinical, laboratory, and imaging features of severe Chlamydia psittaci pneumonia in order to improve early diagnosis and treatment success rates.

METHODS

We conducted a retrospective record review of 14 cases of severe Chlamydia psittaci pneumonia diagnosed by metagenomic next-generation sequencing technology in our hospital. We extracted and analyzed data on the clinical symptoms and signs, contact history, laboratory investigations, chest computed tomography, treatment, and clinical outcomes.

RESULTS

Of the 14 patients, 12 (86%) were male and two (14%) were female, with a mean age of 57 years (SD: 7 years). Eleven patients (79%) had a history of poultry contact. The main clinical manifestations were fever (n = 14, 100%), flu-like symptoms (n = 10, 71%), cough, sputum (n = 9, 64%), and dyspnea (n = 5, 36%). Blood tests revealed marked elevation of neutrophil percentage, C-reactive protein, procalcitonin, brain natriuretic peptide, and creatine kinase levels; slight elevation of aspartate aminotransferase, creatinine, urea, fibrinogen, and D-dimer levels; and decreased albumin, sodium, and calcium levels. Chest computed tomography showed bilateral lesions (n = 7, 50%), middle-lower lobe lesions (n = 10, 71%), lesions in multiple lobes (n = 9, 64%), consolidation shadows (n = 11, 79%), and pleural effusions (n = 11, 79%). The median time from disease onset to hospital admission was 4.5 days (interquartile range: 1-17 days); the mean length of hospital stay was 20.9 ± 8.5 days, and the mean time from admission to diagnosis was 5.1 ± 2.6 days. After diagnosis, patients were either treated with doxycycline alone or doxycycline combined with quinolones. All 14 patients developed respiratory failure and received invasive mechanical ventilation; two (14%) received veno-venous extracorporeal membrane oxygenation, four (29%) received continuous renal replacement therapy, and three (21%) died.

DISCUSSION AND CONCLUSION

A poultry contact history and typical flu-like symptoms are early indicators of Chlamydia psittaci pneumonia. Substantial elevations in procalcitonin, creatine kinase, and brain natriuretic peptide indicate severe disease. Metagenomic next-generation sequencing is useful for diagnosis. Early empirical antibiotic therapy with quinolones can reduce the mortality in critically ill patients.

Successful Treatment of Severe Community-Acquired Pneumonia caused by Chlamydia Psittaci: a Case Report

BACKGROUND

Community acquired pneumonia is a common and deadly condition, which remains a major cause of morbidity and mortality throughout the world. Chlamydia psittaci pneumonia is responsible for less than 5% of community-acquired pneumonia with a fatality rate of 1%. Nonetheless, it is underestimated due to low awareness of the disease and atypical clinical presentation in a majority of the cases. Metagenomic next-generation sequencing can help us diagnose and clarify the etiology in time.

METHODS

We reported a case of an 85-year-old man who presented with intermittent fever and cough with wheezing for 4 days and did a review of related literature.

RESULTS

The patient was admitted to our department due to severe CAP and multiple organ dysfunction. After admission, we applied an empirical antibiotic strategy, performed intubation and invasive ventilation, fluid resuscitation, vasoactive drugs and supportive care. On the third day of admission, metagenomic next-generation sequencing results of blood and bronchoalveolar lavage fluid suggested Chlamydia psittaci. We made a diagnosis of sever Chlamydia psittaci pneumonia and adjusted antibiotics to minocycline combined with azithromycin two days after admission. The patient was successfully cured with a good prognosis.

CONCLUSIONS

Detecting the pathogen as early as possible and achieving accurate diagnosis are essential in infected patients. We can benefit from careful application of metagenomic next-generation sequencing.

Detection of Chlamydia psittaci in both blood and bronchoalveolar lavage fluid using metagenomic next-generation sequencing: A case report

RATIONALE

Chlamydia psittaci (C psittaci) is a gram-negative obligate intracellular parasite, with birds as main hosts. The main route of infection in humans is inhalation of aerosols from contaminated animal excreta through the respiratory tract. The main manifestation of C psittaci infection is pneumonia. Patients suffering from severe infection are prone to sepsis and multiple organ failure. We report a case of simultaneous detection of C psittaci in blood and bronchoalveolar lavage fluid using metagenomic next-generation sequencing (mNGS) technology.

PATIENT CONCERNS

The 71-year-old male patient was a farmer with a long history of raising poultry and initial symptoms of fever and muscle pain accompanied by limb weakness and paroxysmal cough.

DIAGNOSES

The patient was diagnosed with sepsis, severe pneumonia, and multiple organ failure.

INTERVENTIONS

Anti-infective therapy with doxycycline and meropenem was applied.

OUTCOMES

The patient's body temperature and infection indicators improved and the chest X-ray findings showed the amelioration of lesions after 18 days of treatment. The patient was discharged without treatment on hospital day 19 due to financial constraints and subsequently died after 7 days.

LESSONS

mNGS is an excellent diagnostic tool when specific pathogens are undetected by traditional assays.

Use of Real-Time PCR for Chlamydia psittaci Detection in Human Specimens During an Outbreak of Psittacosis - Georgia and Virginia, 2018

Psittacosis is typically a mild febrile respiratory illness caused by infection with the bacterium Chlamydia psittaci and usually transmitted to humans by infected birds (1). On average, 11 psittacosis cases per year were reported in the United States during 2000-2017. During August-October 2018, the largest U.S. psittacosis outbreak in 30 years (82 cases identified*) occurred in two poultry slaughter plants, one each in Virginia and Georgia, that shared source farms (2). CDC used C. psittaci real-time polymerase chain reaction (PCR) to test 54 human specimens from this outbreak. This was the largest number of human specimens from a single outbreak ever tested for C. psittaci using real-time PCR, which is faster and more sensitive than commercially available serologic tests. This represented a rare opportunity to assess the utility of multiple specimen types for real-time PCR detection of C. psittaci. C. psittaci was detected more frequently in lower respiratory specimens (59% [10 of 17]) and stool (four of five) than in upper respiratory specimens (7% [two of 28]). Among six patients with sputum and nasopharyngeal swabs tested, C. psittaci was detected only in sputum in five patients. Cycle threshold (Ct) values suggested bacterial load was higher in lower respiratory specimens than in nasopharyngeal swabs. These findings support prioritizing lower respiratory specimens for real-time PCR detection of C. psittaci. Stool specimens might also have utility for diagnosis of psittacosis.

Multi-organ failure with necrotic skin lesions due to infection with Chlamydia psittaci

Presented is a patient with dyspnea and painful ulcers finally resulting in multi-organ failure. A detailed history resulted in positive PCR testing for Chlamydia psittaci. We emphasize the importance of a definitive history in establishing the correct diagnosis. When clinicians observe dyspnea with multi-organ failure, they should be aware of psittacosis.

Analysis of microRNA expression profiles in human bronchial epithelial cells infected by Chlamydia psittaci

BACKGROUND

Chlamydia psittaci is a pathogen of birds that can cause zoonotic disease in mammals including pneumonia in humans. MicroRNAs (miRNAs) are a class of small non-coding RNA fragments with a length of about 22 nt, which play an important role in regulating gene expression after transcription. Chlamydia infection can cause changes in host cell miRNA expression, but the potential biological function of miRNAs in C. psittaci infection and pathogenesis is not well understood.

METHODS

Small RNA sequencing (sRNA-Seq) technology was used to characterise miRNA expression in human bronchial epithelial (HBE) cells after C. psittaci infection, and differentially expressed miRNAs were identified. Candidate target genes for these miRNAs were then functionally annotated by Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. The sRNA-Seq results were partially validated by quantitative real time polymerase chain reaction (qRT-PCR) and miRNA-target networks were constructed using visualization software.

RESULTS

We identified 151 differentially expressed miRNAs (46 known miRNAs and 105 novel miRNAs) in C. psittaci-infected HBE cells, of which 140 were upregulated and 11 were downregulated. Of these, 17 known miRNAs were significantly upregulated and two were downregulated using P < 0.05 and |log₂FoldChange|>1.5 as threshold criteria. GO enrichment results showed that the predicted targets of these differentially expressed miRNAs were mainly involved in transcriptional regulation and ATP binding. KEGG pathway analysis suggested that the candidate target genes were involved in several important signaling pathways such as MAPK, ErbB, cGMP-PKG, cAMP, mTOR, GNRH, oxytocin, PI3K-Akt and AMPK, which are primarily related to biological processes such as transcription and signal transduction. The qRT-PCR results for miR-2116-3p, miR-3195, miR-663a, miR-10401-5p, miR-124-3p, miR-184, miR-744-5p and hsa-miR-514b-5p were consistent with the sRNA-Seq data.

CONCLUSIONS

A large amount of miRNA expression profile data relating to C. psittaci infection was obtained, which provides a useful experimental and theoretical basis for further understanding the pathogenic mechanisms of C. psittaci infection.

A 25-year retrospective study of Chlamydia psittaci in association with equine reproductive loss in Australia

Introduction. Chlamydia psittaci is primarily a pathogen of birds but can also cause disease in other species. Equine reproductive loss caused by C. psittaci has recently been identified in Australia where cases of human disease were also reported in individuals exposed to foetal membranes from an ill neonatal foal in New South Wales.Hypothesis/Gap Statement. The prevalence of C. psittaci in association with equine reproductive over time and in different regions of Australia is not known.Aim. This study was conducted to detect C. psittaci in equine abortion cases in Australia using archived samples spanning 25 years.Methodology. We tested for C. psittaci in 600 equine abortion cases reported in Australia between 1994 to 2019 using a Chlamydiaceae real-time quantitative PCR assay targeting the 16S rRNA gene followed by high-resolution melt curve analysis. Genotyping and phylogenetic analysis was performed on positive samples.Results. The overall prevalence of C. psittaci in material from equine abortion cases was 6.5 %. C. psittaci-positive cases were detected in most years that were represented in this study and occurred in Victoria (prevalence of 7.6 %), New South Wales (prevalence of 3.9 %) and South Australia (prevalence of 15.4 %). Genotyping and phylogenetic analysis showed that the C. psittaci detected in the equine abortion cases clustered with the parrot-associated 6BC clade (genotype A/ST24), indicating that infection of horses may be due to spillover from native Australian parrots.Conclusion. This work suggests that C. psittaci has been a significant agent of equine abortion in Australia for several decades and underscores the importance of taking appropriate protective measures to avoid infection when handling equine aborted material.

A recombinase polymerase amplification-based assay for rapid detection of Chlamydia psittaci

Chlamydia psittaci is a zoonotic agent of systemic wasting disease in birds and atypical pneumonia in mammalians including humans, constituting a public health risk. A rapid diagnostic assay would be beneficial in screening C. psittaci in the field. In this study, we developed a probe-based recombinase polymerase amplification (RPA) assay for the rapid detection of C. psittaci. The specific primer pairs and probe targeting the conserved region of the outer membrane protein A gene were designed and applied to the real-time real-time RPA assay. The test can be performed at 39°C for 20 min using a portable device, with sensitivities approaching 100 copies of DNA molecules per reaction, with no cross-reaction with other pathogens. The clinical performance of the RPA assay was evaluated in an outbreak of C. psittaci and has high accuracy levels in field applications. The epidemic C. psittaci strains were classed into 2 genotypes: A and C. Collectively, this study offers a promising approach in screening for C. psittaci both in a laboratory setting and in field settings, and RPA can be used as an effective clinical test to monitor outbreaks in domestic fowl populations.

Phylogenetic analyses of Chlamydia psittaci ompA gene sequences from captive blue-fronted Amazon parrots (Amazona aestiva) with hepatic disease in Brazil

Chlamydia psittaci was detected in 152 (72%) blue-fronted Amazon parrots (Amazona aestiva, parrot from the Psittacidae family) out of a population of 212 that died during 2009-2011 in a wildlife rescue and rehabilitation centre in Minas Gerais, Brazil, following rescue from illegal wildlife trafficking. The macroscopic changes observed in these animals were hepatomegaly with multifocal white foci visible at the serosal surfaces of the liver, and extending into the parenchyma, and splenomegaly. The microscopic lesions observed in the liver included multifocal to coalescing miliary necrosis of hepatocytes with infiltration by heterophils, lymphocytes and plasma cells. In the spleen, loss of the normal architecture and infiltration by macrophages and plasma cells were observed. Stained tissue sections (Gimenez technique) revealed small round clusters suggestive of C. psittaci (reticulate bodies) in the cytoplasm of macrophages from the liver and spleen. Nine sequences of segments of the ompA gene, obtained from different individuals, were randomly selected for sequencing. The phylogenetic analyses showed that all strains clustered with genotype A, which is the most virulent genotype for birds. This genotype is involved in mortality of psittacines, is easily transmitted in captivity and represents a problem for successful rehabilitation. The results indicate the necessity to improve biosecurity in triage and to provide individual personal protection for professionals and caretakers.

Development of a Plasmid Shuttle Vector System for Genetic Manipulation of Chlamydia psittaci

The obligate intracellular bacterium Chlamydia psittaci is a known avian pathogen causing psittacosis in birds and is capable of zoonotic transmission. In human pulmonary infections, C. psittaci can cause pneumonia associated with significant mortality if inadequately diagnosed and treated. Although intracellular C. psittaci manipulates host cell organelles for its replication and survival, it has been difficult to demonstrate host-pathogen interactions in C. psittaci infection due to the lack of easy-to-handle genetic manipulation tools. Here, we show the genetic transformation of C. psittaci using a plasmid shuttle vector that contains a controllable gene induction system. The 7,553-bp plasmid p01DC12 was prepared from the nonavian C. psittaci strain 01DC12. We constructed the shuttle vector pCps-Tet-mCherry using the full sequence of p01DC12 and the 4,449-bp fragment of Chlamydia trachomatis shuttle vector pBOMB4-Tet-mCherry. pCps-Tet-mCherry includes genes encoding the green fluorescent protein (GFP), mCherry, and ampicillin resistance (AmpR). Target genes can be inserted at a multiple cloning site (MCS). Importantly, these genes can be regulated by a tetracycline-inducible (tet) promoter. Using the pCps-Tet-mCherry plasmid shuttle vector, we show the expression of GFP, as well as the induction of mCherry expression, in C. psittaci strain 02DC15, which belongs to the avian C. psittaci 6BC clade. Furthermore, we demonstrated that pCps-Tet-mCherry was stably retained in C. psittaci transformants. Thus, our C. psittaci plasmid shuttle vector system represents a novel targeted approach that enables the elucidation of host-pathogen interactions.IMPORTANCE Psittacosis, caused by avian C. psittaci, has a major economic impact in the poultry industry worldwide and represents a significant risk for zoonotic transmission to humans. In the past decade, the tools of genetic manipulation have been improved for chlamydial molecular studies. While several genetic tools have been mainly developed in Chlamydia trachomatis, a stable gene-inducible shuttle vector system has not to date been available for C. psittaci In this study, we adapted a C. trachomatis plasmid shuttle vector system to C. psittaci We constructed a C. psittaci plasmid backbone shuttle vector called pCps-Tet-mCherry. The construct expresses GFP in C. psittaci Importantly, exogeneous genes can be inserted at an MCS and are regulated by a tet promoter. The application of the pCps-Tet-mCherry shuttle vector system enables a promising new approach to investigate unknown gene functions of this pathogen.

SURVEILLANCE FOR CHLAMYDIA SPP. WITH MULTILOCUS SEQUENCE TYPING ANALYSIS IN WILD AND CAPTIVE BIRDS IN VICTORIA, AUSTRALIA

Chlamydia psittaci typically infects birds and can cause outbreaks of avian chlamydiosis, but it also has the potential to cause zoonotic disease (psittacosis) in humans. To better understand the epidemiology of C. psittaci in Victoria, Australia, we conducted opportunistic sampling of more than 400 wild and captive birds presented to the Australian Wildlife Health Centre at Zoos Victoria's Healesville Sanctuary for veterinary care between December 2014 and December 2015. Samples were screened for the presence of chlamydial DNA using quantitative PCR, and positive samples were subjected to multilocus sequence typing analysis. The results showed a significantly higher prevalence of infection in captive birds (8%; 9/113) compared to wild birds (0.7%; 2/299). Multilocus sequence typing analysis revealed that C. psittaci sequence type 24 was detected in both wild and captive birds in the local region, while C. psittaci sequence type 27 was detected for the first time in an Australian avian host. The generally low prevalence of C. psittaci detection points to a generally low zoonotic risk to veterinary and support staff, although this risk may be higher when handling captive birds, where the prevalence of C. psittaci infection was almost 10-fold higher. Even with low rates of C. psittaci detection, appropriate hygiene and biosecurity practices are recommended due to the serious human health implications of infection with this pathogen.

Chlamydiaceae in wild, feral and domestic pigeons in Switzerland and insight into population dynamics by Chlamydia psittaci multilocus sequence typing

Feral pigeons, common wood pigeons and Eurasian collared doves are the most common representatives of the Columbidae family in Switzerland and are mostly present in highly populated, urban areas. Pigeons may carry various members of the obligate intracellular Chlamydiaceae family, particularly Chlamydia (C.) psittaci, a known zoonotic agent, and C. avium. The objective of the study was to identify the infection rates of common free-roaming pigeons for different Chlamydia species with the overall aim to assess the risk pigeons pose to public health. In this study, 431 pigeons (323 feral pigeons, 34 domestic pigeons, 39 Eurasian collared doves, 35 common wood pigeons) from several geographic locations in Switzerland were investigated for the presence of Chlamydiaceae. Samples consisted of pooled choanal-cloacal swabs (n = 174), liver samples (n = 52), and paired swab and liver samples from 205 pigeons (n = 410). All 636 samples were screened using a Chlamydiaceae family-specific 23S rRNA real-time PCR (qPCR). Subsequent species identification was performed by DNA-microarray assay, sequencing of a 16S rRNA gene fragment and a C. psittaci specific qPCR. In total, 73 of the 431 pigeons tested positive for Chlamydiaceae, of which 68 were positive for C. psittaci, four were C. avium-positive and one pigeon was co-infected with C. avium and C. psittaci. The highest infection rates were detected in feral (64/323) and domestic pigeons (5/34). Common wood pigeons (2/35) and Eurasian collared doves (2/39) revealed lower infection rates. Additionally, multilocus sequence typing of twelve selected C. psittaci-positive samples revealed closely related sequence types (ST) between and within different Swiss cities. Furthermore, liver and corresponding swab samples from the same bird were colonized by the same ST. Considering the high infection rates of C. psittaci in domestic and feral pigeons, close or frequent contact to these birds poses a human health risk.

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.

Chlamydiosis in farmed chickens in Slovakia and zoonotic risk for humans

INTRODUCTION

Chlamydia psittaci is an obligate intracellular Gram-negative bacterium causing respiratory disease (chlamydiosis) or asymptomatic carriage in poultry. In humans, it is a zoonotic agent of ornithosis/psittacosis. Due to low awareness of the disease and variable clinical presentation, psittacosis is often remains unrecognised as such by general practitioners. Zoonotic transfer occurs through inhalation of contaminated aerosols, and originates from feathers, faecal material and respiratory tract exudates.

OBJECTIVE

The aim of this study was to investigate chickens for the presence of Chlamydia sp. from pharyngeal and cloacal swabs and review the zoonotic risk for humans.

MATERIAL AND METHODS

138 clinically healthy chickens from farms in Slovakia were examined for the presence of Chlamydia sp. The age of the chickens was 6 months. Two different samples were used - pharyngeal swabs and cloacal swabs. Each sample was examined by the molecular PCR method, and in the case of a positive result the identity of the obtained sequences was examined by a BLAST search.

RESULTS

Of the total number of 276 examined samples from 138 chickens, 19 (6.9%) showed positivity for C. psittaci infection, 12 (8.7%) which were positive from pharyngeal swabs and 7 (5.1%) from cloacal swabs. None of the chickens were positive in both samples. Phylogenetic examination of the 19 isolates identified in the study, based on the 23S rRNA gene sequence, revealed that the isolates obtained were identical with C. psittaci, and genetically very close to genotypes B and genotype E.

CONCLUSIONS

C. psittaci infections are apparently emerging in chickens. Chicken-processing plant employees should be considered a risk group for human psittacosis. There is a need for higher awareness and for efficient risk assessment and management.

Development of a Novel PmpD-N ELISA for Chlamydia psittaci Infection

OBJECTIVE

Chlamydia psittaci is an avian respiratory pathogen and zoonotic agent. The wide prevalence of C. psittaci poses a threat to the poultry industry and its employees. However, few commercial kits are available for detecting avian antibodies excluding the in-house ELISA kit. In this study, we developed a novel ELISA kit for detecting antibodies against C. psittaci based on the N-terminal fragment of polymorphic outer membrane protein D (PmpD-N) as the coating antigen.

METHODS

The antigen concentrations, primary antibody, and cut-off value were determined and optimized. The ELISA, designated PmpD-N ELISA, was assessed for sensitivity, specificity, and concordance using sera samples from 48 experimentally infected and 168 uninfected SPF chickens.

RESULTS

The sensitivity and specificity of PmpD-N ELISA were 97.9%, 100%, respectively, while the concordance was 98.1% as compared to that of MOMP-ELISA. No cross-reaction with positive sera for other avian pathogens was found. Using PmpD-N ELISA, 799/836 clinical samples were positive, including 93.0% and 98.1% positivity in layers and broilers, respectively.

CONCLUSION

These data indicate that indirect ELISA with PmpD-N as the antigen candidate is a promising approach for the surveillance of C. psittaci infection.

Chlamydia psittaci: a relevant cause of community-acquired pneumonia in two Dutch hospitals

BACKGROUND

Of all hospitalised community-acquired pneumonias (CAPs) only a few are known to be caused by Chlamydia psittaci. Most likely the reported incidence, ranging from of 0% to 2.1%, is an underestimation of the real incidence, since detection of psittacosis is frequently not incorporated in the routine microbiological diagnostics in CAP or serological methods are used.

METHODS

C. psittaci real-time polymerase chain reaction (PCR) was routinely performed on the sputum of 147 patients hospitalised with CAP, who participated in a clinical trial conducted in two Dutch hospitals. In 119/147 patients the paired complement fixation test (CFT) was also performed for the presence of Chlamydia antibodies. Positive CFTs were investigated by micro- Immunofluorescence for psittacosis specificity. Case criteria for psittacosis were a positive PCR or a fourfold rise of antibody titre in CFT confirmed by micro- Immunofluorescence. Furthermore, we searched for parameters that could discriminate psittacosis from CAPs with other aetiology.

RESULTS

7/147 (4.8%) patients were diagnosed with psittacosis: six with PCR and one patient with a negative PCR, but with CFT confirmed by micro- Immunofluorescence. Psittacosis patients had had a higher temperature (median 39.6 vs. 38.2 °C;) but lower white blood cell count (median 7.4 vs. 13.7 x 109/l) on admission compared with other CAP patients.

CONCLUSION

In this study, C. psittaci as CAP-causing pathogen was much higher than previously reported. To detect psittacosis, PCR was performed on all CAP patients for whom a sputum sample was available. For clinical use, PCR is a fast method and sputum availability allows genotyping; additional serology can optimise epidemiological investigations.

Localization and characterization of two putative TMH family proteins in Chlamydia psittaci

Chlamydia psittaci (C. psittaci), an obligate intracellular agent of psittacosis, causes an atypical pneumonia in humans. The transmembrane head proteins (TMH) of C. psittaci, putatively belong to the Inc family and presumably play similar roles. CPSIT_0844 and CPSIT_0846 were the putative TMH proteins of C. psittaci. To identify these two proteins, antisera were raised with fusion proteins which were prokaryotic expressed in Escherichia coli and purified. By immunofluorescence assay, CPSIT_0844 and CPSIT_0846 were localized in the inclusion membrane of C. psittaci-infected cells. By RT-PCR and western blot analysis to detect the temporal expression, CPSIT_0844 and CPSIT_0846 were detected as early as 12h post-infection (p.i.) and 6h p.i., separately; meanwhile, in secretions monitored with immunofluorescence assay, these proteins were observed in the inclusion membrane at 18h p.i. and remained in the inclusion membrane throughout the growth cycle. CPSIT_0844 and CPSIT_0846 could specifically be recognized by the antiserum of C. psittaci but failed to react with the antiserums of Chlamydia trachomatis and Chlamydia pneumoniae, which is consistent with the fact that they had no significant orthologs in C. trachomatis and C. pneumoniae. These results revealed that CPSIT_0844 and CPSIT_0846, the putative TMH family proteins, might be unique to C. psittaci and could be used to diagnose the infection caused by C. psittaci. Moreover, CPSIT_0844 and CPSIT_0846 could induce the expression of the inflammatory cytokines IL-1β, IL-6 and TNF-α in THP-1 cells, which might contribute to chlamydia-induced inflammatory pathologies.

Chlamydiosis in British Garden Birds (2005-2011): retrospective diagnosis and Chlamydia psittaci genotype determination

The significance of chlamydiosis as a cause of mortality in wild passerines (Order Passeriformes), and the role of these birds as a potential source of zoonotic Chlamydia psittaci infection, is unknown. We reviewed wild bird mortality incidents (2005-2011). Where species composition or post-mortem findings were indicative of chlamydiosis, we examined archived tissues for C. psittaci infection using PCR and ArrayTube Microarray assays. Twenty-one of 40 birds tested positive: 8 dunnocks (Prunella modularis), 7 great tits (Parus major), 3 blue tits (Cyanistes caeruleus), 2 collared doves (Streptopelia decaocto, Order Columbiformes), and 1 robin (Erithacus rubecula). Chlamydia psittaci genotype A was identified in all positive passerines and in a further three dunnocks and three robins diagnosed with chlamydiosis from a previous study. Two collared doves had genotype E. Ten of the 21 C. psittaci-positive birds identified in the current study had histological lesions consistent with chlamydiosis and co-localizing Chlamydia spp. antigens on immunohistochemistry. Our results indicate that chlamydiosis may be a more common disease of British passerines than was previously recognized. Wild passerines may be a source of C. psittaci zoonotic infection, and people should be advised to take appropriate hygiene precautions when handling bird feeders or wild birds.

[Ornithosis is a diagnostic challenge]

Symptoms of ornithosis are often unspecific and vary in severity. This case report illustrates the challenges in diagnosing ornithosis. It also shows how easy it is to diagnose ornithosis by PCR analysis of a sputum sample and that it is not always possible to base the diagnosis on serology as our patient had negative serology tests even four weeks after hospitalization. The diagnosis was furthermore compounded by an underlying chronic lung disease. To diagnose patients with respiratory problems correctly it is important to analyse lower respiratory samples by PCR along with other diagnostic tests and to get a detailed medical history.

High prevalence of Chlamydophila psittaci subclinical infection in Italian patients with Sjögren's syndrome and parotid gland marginal zone B-cell lymphoma of MALT-type

OBJECTIVES

To assess Chlamydophila psittaci (Cp) subclinical infection in patients with Sjögren's syndrome (SS).

METHODS

Seventy-four SS patients (55.4 ±13.4 yrs; 94.6% females) were studied. Among them, 18 had salivary gland mucosa-associated lymphoid tissue (MALT) B-cell lymphoma, 20 myoepithelial sialoadenitis (MESA), and 36 no lymphoproliferative disorders (LPD). The presence of Cp DNA was assessed in peripheral blood of all patients by specific PCR protocols. Paired salivary gland samples were also investigated whenever available (34 cases), including lymphomatous and non-lymphomatous samples, as well as major and minor salivary gland tissues. As controls, 225 blood donors were analysed in the peripheral blood.

RESULTS

Overall, Cp DNA was detected in 11/74 (14.9%) SS patients vs. 1/225 (0.4%) controls (p<0.0001). Cp was detected at higher frequency in MALT lymphoma patients (6/18, 33.3%), as compared with MESA (3/20, 15%) or patients without LPD (2/36, 5.6%), (MALT lymphomas vs. others: p=0.02). A similar Cp prevalence was observed in blood vs. salivary gland tissues, however with a higher frequency in the major than in the minor salivary glands (5/18, 27.8%, vs. 1/17, 5.9%, p=0.18). Cp-positive patients were all rheumatoid factor positive (11/11, 100% vs. 40/63, 63.5% Cp-negative; p=0.014), while no difference was noticed for anti-SSA/SSB positivity.

CONCLUSIONS

In the light of accepted models of MALT B-cell lymphomagenesis and considering previous data implicating Cp infection in ocular adnexa MALT lymphoma, our results suggest that Cp infection could be involved also in a fraction of patients with SS developing lymphoma. The potential therapeutic implications of these findings appear worthwhile.

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.

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.

Chlamydophila psittaci subclinical infection in chronic polyarthritis

OBJECTIVES

Recent evidence indicates that Chlamydophila psittaci (Cp) may establish chronic infections, which may promote autoimmunity and/or B cell lymphoproliferation.

METHODS

The presence of a subclinical Cp infection was investigated in 293 patients with chronic inflammatory polyarthritis, including 175 patients with rheumatoid factor (RF)-positive and/or anti-CCP-positive rheumatoid arthritis (RA) and 118 with seronegative polyarthritis (46 RF-negative/anti-CCP-negative RA, 36 psoriatic arthritis and 36 undifferentiated spondyloarthritis). One hundred and eighty-five healthy controls were also investigated. The presence of Cp infection was assessed in peripheral blood mononuclear cells using several PCR protocols targeting different regions of the Cp genome (16S-23S spacer rRNA, OMP-A, and Gro-EL). The DNA of other Chlamydia species (C. Pneumoniae and C. Trachomatis) was also investigated. Amplicons were sequenced to confirm the specificity of PCR products.

RESULTS

The presence of a subclinical chronic Cp infection was observed in a significantly higher percentage of patients with chronic polyarthritis (38/293; 13%) compared to healthy controls (1/185, 0.5%; OR=27.4, 95%CI:3.73-201.6, p<0.0001). Furthermore, the prevalence of Cp was higher in seronegative polyarthritis (23/118; 19.5%) than in seropositive RA patients (15/175; 7.4%; OR=2.58, 95%CI: 1.28-5.19, p=0.0078). The highest prevalence of Cp infection was found in RF/anti-CCP double-negative RA patients (13/46, 28.3%), followed by patients with psoriatic arthritis (6/36; 16.7%). No differences in age, sex, disease duration and undergoing therapies were noticed between Cp-positive and Cp-negative patients; nor between seropositive and seronegative patients.

CONCLUSIONS

Cp may be an infectious trigger possibly involved in the pathogenesis of a fraction of inflammatory polyarthritis, particularly in seronegative patients.

Multi locus sequence typing of Chlamydia reveals an association between Chlamydia psittaci genotypes and host species

Chlamydia comprises a group of obligate intracellular bacterial parasites responsible for a variety of diseases in humans and animals, including several zoonoses. Chlamydia trachomatis causes diseases such as trachoma, urogenital infection and lymphogranuloma venereum with severe morbidity. Chlamydia pneumoniae is a common cause of community-acquired respiratory tract infections. Chlamydia psittaci, causing zoonotic pneumonia in humans, is usually hosted by birds, while Chlamydia abortus, causing abortion and fetal death in mammals, including humans, is mainly hosted by goats and sheep. We used multi-locus sequence typing to asses the population structure of Chlamydia. In total, 132 Chlamydia isolates were analyzed, including 60 C. trachomatis, 18 C. pneumoniae, 16 C. abortus, 34 C. psittaci and one of each of C. pecorum, C. caviae, C. muridarum and C. felis. Cluster analyses utilizing the Neighbour-Joining algorithm with the maximum composite likelihood model of concatenated sequences of 7 housekeeping fragments showed that C. psittaci 84/2334 isolated from a parrot grouped together with the C. abortus isolates from goats and sheep. Cluster analyses of the individual alleles showed that in all instances C. psittaci 84/2334 formed one group with C. abortus. Moving 84/2334 from the C. psittaci group to the C. abortus group resulted in a significant increase in the number of fixed differences and elimination of the number of shared mutations between C. psittaci and C. abortus. C. psittaci M56 from a muskrat branched separately from the main group of C. psittaci isolates. C. psittaci genotypes appeared to be associated with host species. The phylogenetic tree of C. psittaci did not follow that of its host bird species, suggesting host species jumps. In conclusion, we report for the first time an association between C. psittaci genotypes with host species.

Chlamydophila psittaci infections in The Netherlands

Psittacosis, caused by Chlamydophila psittaci, is a well described but sporadically occurring clinical entity, which mainly presents as community-acquired pneumonia. Diagnosis used to be relatively difficult. However, new molecular techniques, such as real-time polymerase chain reaction, increased detection of cases. Furthermore, genotyping of the ompA gene can be used as a tool to trace the possible source of an outbreak or to link a specific bird to a particular patient.

[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.

Low prevalence ofChlamydia psittaciin ocular adnexal lymphomas from Cuban patients

Most ocular adnexal lymphomas (OAL) are extranodal marginal zone B-cell lymphomas (EMZL) of mucosa-associated lymphoid tissue (MALT)-type. Chronic antigen stimulation has been suggested to have a pathogenetic role in EMZL and Chlamydia psittaci chronic infection has been recently associated with the development of OAL in a series of patients from Italy. To assess this association, an evaluation of the presence of C. psittaci was made in a different OAL population. DNA samples were obtained from formalin-fixed, paraffin-embedded sections samples of 26 patients with OAL, 20 non-OAL and 20 benign ocular lesions, diagnosed and treated between 1998 and 2003 at National Institute of Oncology in Havana, Cuba. All samples were histologically reviewed by an expert pathologist. Fluorescence in situ hybrization (FISH) analysis of translocations involving MALT1 was performed. The presence of bacterial DNA was assessed with a multiplex touchdown enzyme time release polymerase chain reaction. DNA sequencing was performed to confirm suspicious bands. Seventy-three percent of the OAL cases were EMZL and 81% were in stage IE. FISH analysis was performed in 13 OAL cases and none of them evidenced MALT1 translocations. DNA of C. psittaci was detected in 11% of the 46 lymphomas: two orbital EMZL and three non-OAL. All 20 benign ocular lesions were negative for C. psittaci. The low prevalence of C. psittaci in OAL suggests geographical differences in the etiology of this entity. International studies are needed to clarify the role of C. psittaci in OALs.

Lack of an association betweenChlamydia psittaciand ocular adnexal lymphoma

The objective of this study was to assess whether there is PCR evidence for C. psittaci DNA in ocular adnexal lymphoma specimens collected in an academic institution in the U.S. This was a retrospective, single-center study of patients from 1994 - 2004. We used 28 ocular adnexal lymphoma biopsy specimens from adult patients, 16 control lymphoma specimens from patients with systemic lymphomas not involving the ocular adnexa, and five control benign adnexal tissue samples. The presence of C. psittaci DNA was investigated by polymerase chain reaction (PCR) in each group. Two different assays were utilized: (1) conventional PCR/gel based assay targeting a 111-bp fragment of the 16S gene and (2) a real-time PCR assay amplifying a 148-bp portion of the 16S gene with detection via a specific fluorescent probe. Amplification was carried out to 60 cycles. Positive controls consisted of isolated DNA from C. psittaci strains VS1, CP3, and FP. A human DNA internal control was used to assess sample DNA quality and amplification success. Mean outcome measure was the presence of C. psittaci DNA. Using both assays, all patient samples in all categories yielded negative results. Both assays detected C. psittaci DNA from isolated strains. Internationally, Chlamydia psittaci has been associated with ocular adnexal lymphomas with great variability. Similar to several other recent studies in the USA, our study could not confirm the presence of C. psittaci in ocular adnexal lymphomas. Differences in the prevalence of C. psittaci infection in various geographic regions or technical differences in the application of the assays may underlie the variability in the association between C. psittaci and ocular adnexal lymphoma.

DNA microarray-based genotyping of Chlamydophila psittaci strains from culture and clinical samples

The avian and human pathogen Chlamydophila (C.) psittaci represents a genetically heterogeneous species. To facilitate epidemiological surveys, more rapid yet highly specific molecular tests are needed. Currently used typing methods, i.e. serotyping and PCR-RFLP, have only limited sensitivity and are incapable of covering the wide spectrum of naturally occurring types of C. psittaci strains. In the present study, a new DNA microarray assay based on the ArrayTube (AT) technology was used to genotype C. psittaci in 98 isolates and 23 clinical tissue samples. The present array carries 35 oligonucleotide probes derived from variable domains 2 and 4 of the ompA gene. The assay proved highly sensitive, allowing correct genotyping of DNA from 2 inclusion-forming units. The results of DNA microarray genotyping of cultured strains proved highly concordant with the data from PCR-RFLP typing and serotyping. Sequencing of the ompA gene served as the reference test to verify the accuracy of AT genotyping results. In 15 instances (15.3%), strains were successfully typed by the AT assay, while serotyping and/or PCR-RFLP genotyping failed to produce unambiguous results. Eleven of these samples were ompA sequenced to confirm the AT findings. In addition to the currently accepted nine ompA genotypes, the microarray test was shown to recognise new provisional genotypes, such as Mat116 and YP84. In conclusion, the new AT assay proved to be suitable for rapid, sensitive and reproducible genotyping of C. psittaci strains and can be recommended for routine diagnosis.

[Molecular genetic characterization of avian Chlamydophila psittaci isolates]

Restriction enzyme analysis of the omp1 gene was used to characterize 51 avian Chlamydophila psittaci isolates. The analysis confirmed the predominance of genotype A in parrot C. psittaci isolates and revealed new omp1 genotypes in corvid C. psittaci isolates. The corvid isolates proved to lack an extrachromosomal plasmid. The omp1 and rRNA IGS sequences were determined for the new isolates. Phylogenetic analysis showed that isolate 1V, obtained from a crow, is intermediate in several characters between C. abortus and C. psittaci. The results were compared with data on the phylogenetic relationships of earlier chlamydium isolates.