Prevalence and genotypes of Chlamydia psittaci in pet birds of Hong Kong.

Psittacosis, or parrot fever, is a zoonotic disease caused by Chlamydia species associated with birds. One of the causative agents of the disease is Chlamydia psittaci, which is commonly carried by psittacine and other bird species, can be highly pathogenic and virulent to humans. In Hong Kong, a city with high population density, psittacosis is a notifiable disease with over 60% of cases in the last decade resulting in hospitalization. However, the sources of transmission of C. psittaci and its prevalence in pet birds in Hong Kong are currently unknown. To evaluate the risks of psittacosis transmission through pet birds, we tested the presence of C. psittaci and determined its genotypes in samples obtained from 516 captive birds from households, pet shops, and a veterinary hospital in Hong Kong. Results revealed that five samples (0.97%), collected from budgerigars and cockatiels, were C. psittaci-positive, while four (80%) of them were obtained from pet shops. Our phylogenetic analysis revealed that all identified strains belonged to Genotype A and showed high similarity to other sequences of this genotype obtained from various geographical locations and host species, including mammals. Our findings provide evidence for the presence of Chlamydia psittaci and shed light on its sources in captive birds in Hong Kong. They highlight the potential zoonotic risks associated with this pathogen, which can affect both humans and wild birds.

Prevalence and genotypes of Chlamydia psittaci in birds and related workers in three cities of China.

Chlamydia psittaci-a zoonotic pathogen in birds-may be transmitted to humans, causing severe respiratory disease. Individuals working in or living near poultry farms are highly susceptible to C. psittaci infection. In this study, we assessed the prevalence and genotypes of C. psittaci in poultries and humans in three cities of China by collecting fecal samples from different poultry species and throat swab samples and serum samples from workers in poultry farms and zoos. These samples were screened by real-time fluorescence quantitative PCR (qPCR) targeting C. psittaci ompA. The positive samples were subjected to PCR amplification and sequencing of ompA. The strains detected in the samples were genotyped on the basis of the phylogenetic analysis of ompA sequences. In total, 3.13% (40/1278) poultry fecal samples were positive in the qPCR assay, whereas 3.82% (6/157) of throat swab samples and 42.59% (46/108) of serum samples from the workers were positive in the qPCR and indirect fluorescent antibody assays, respectively. The strains detected in the 32 poultry samples and 6 human samples were genotyped as type A, indicating that the workers were infected with C. psittaci that originated in poultry birds in farms. Additionally, eight peacocks showed strains with the genotype CPX0308, which was identified in China for the first time. Elucidating the distribution of C. psittaci in animals and poultry-related workers may provide valuable insights for reducing the risk of C. psittaci infection within a population.

The therapeutic efficacy of neem (Azadirecta indica) leaf extract against coinfection with Chlamydophila psittaci and low pathogenic avian influenza virus H9N2 in broiler chickens.

Avian chlamydiosis is a serious avian infection that carries a significant zoonotic danger to the poultry industry. The respiratory co-infections caused by the low pathogenic avian influenza virus H9N2 (LPAIV H9N2) also cause significant financial losses in the poultry industry. The purpose of this study was to examine the pathogenicity of Chlamydophila psittaci, and LPAIV H9N2 individually and in combination in broiler chickens, as well as to determine whether or not aqueous neem (Azadirachta indica) leaf extract is effective against infections caused by these pathogens. Therefore, 120 broiler cobb chicks were equally divided into 4 groups (30 birds each) with triplicates with 10 birds. Broilers in group 1 (G1) were infected with only C. psittaci, broilers in group 2 (G2) were infected with only LPAIV H9N2, broilers in group 3 (G3) were infected with C. psittaci and LPAIV H9N2, and broilers in group 4 (G4) remained not challenged and non-treated with any therapeutic or preventive treatment (negative control). At 21 d postinfection (dpi), birds in G1, G2, and G3 were divided into 3 subgroups of 10 birds each: subgroup (A) remained infected and untreated (positive control), subgroup (B) infected and received oxytetracycline for 5 consecutive d, and subgroup (C) infected and received 8% aqueous neem leaf extract for 5 consecutive d. The multiplication of C. psittaci in birds in G1, in various tissues was evaluated using Giemsa staining and the data showed that multiplication was much higher in the lung, spleen, and liver from 6 h to 21 dpi, but low in the heart from 8 to 21 dpi. During simultaneous co-infection in G3, the birds developed significant clinical symptoms and postmortem lesions (PM). Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect viral shedding from oropharyngeal and cloacal swabs between 2 dpi and 8 dpi, with cycle threshold (CT) values ranging from 22 to 24. In contrast, bacterial shedding began 6 h after infection and continued until 21 dpi, with CT values ranging from 23 to 26. Administration of an aqueous neem leaf extract at an 8% concentration (Group C) resulted in a numerical rise in average body weight across all treatment groups in the third and fourth week, as well as a reduction in LPAIV H9N2 and C. psittaci replication in the respiratory and gut of treated birds compared to those treated with oxytetracycline (Group B). Overall, respiratory co-infections pose a considerable risk to the poultry business, which is a big threat. To control C. psittaci and LPAIV H9N2 in broiler chickens, oral supplementation of 8% aqueous neem leaf extract is recommended. This treatment improves the birds' performance, as evidenced by an increase in their average body weight. In addition, the application of 8% aqueous neem leaf extract lowers C. psittaci replication within tissues and diminishes LPAIV H9N2 shedding.

A novel variant of Chlamydia psittaci causing human psittacosis in China.

From January 2022 to November 2022, sporadic psittacosis occurred in Lishui city, China. The patients were presented with fever, cough, and pulmonary infiltration. Their clinical symptoms were not relieved after receiving cephalosporin, penicillin, beta-lactamase inhibitors, and quinolones. Metagenomic next-generation sequencing of bronchoalveolar lavage fluid samples from the patients revealed Chlamydia psittaci infection. Then, three C. psittaci strains were isolated from the patients. Their whole genome sequences (WGSs) were obtained, and a core genome multilocus sequence typing (cgMLST) method was developed to study the population structure of C. psittaci. Using the constructed cgMLST method, 72 WGSs were divided into four related groups and ten sub-clusters. The Lishui strains formed a unique population of C. psittaci, which might represent a new variant of C. psittaci. In vitro antimicrobial susceptibility testing suggested that the Lishui strains were sensitive to tetracycline, macrolides, quinolones, and no drug-resistance was observed.

Serum C-reactive protein to albumin ratio as a potential risk indicator of pneumonia caused by Chlamydia psittaci: a multicenter retrospective study.

Introduction: The aim of the study was to describe psittacosis pneumonia and to assess the predictive value of the C-reactive protein/albumin ratio in psittacosis pneumonia for severity. Methods: Data on psittacosis pneumonia cases diagnosed using metagenomic sequencing were collected from three hospitals in Shanghai, China from Oct. 2019 to Oct. 2022. Serum levels of C-reactive protein and albumin were measured and the C-reactive protein to albumin ratio (CAR) was calculated. Spearman's correlation analysis, ordered logistic regression analysis, and receiver operating characteristic curve analysis were conducted to examine the correlation and predictive ability of the three indicators on the severity of the disease. Results: A total of 27 patients with psittacosis pneumonia were enrolled, with an average age of 62 years and 70.4% being male. 44.4% of patients had a clear history of contact with poultry or birds. The predominant symptom was fever (100%). Patients treated in the respiratory intensive care unit (RICU) had a higher likelihood of experiencing wheezing (88.9% versus 33.3%, P=0.013) and chest tightness (88.9% vs. 33.3%, P=0.013) than those in the general ward (Non-RICU). The proportion of patients with pleural effusion was significantly higher in the RICU compared to the Non-RICU (88.9% vs. 38.9%, P=0.019). The RICU group had a significantly higher CAR than the Non-RICU group (9.41 vs. 4.05, P=0.017). This result was accompanied by higher intubation and ventilator support (33.3% vs. 0.0%, P=0.029), higher PCT and CRP levels and lower albumin and PaCO2 levels in the RICU than in the Non-RICU. Logistic regression analysis indicated that CAR (OR 1.49; 95% CI 1.07-2.06, P=0.017) was risk factor for prolonged hospitalization (> 14 days). Discussion: Elevated serum CAR levels were found to be associated with a greater risk of severe psittacosis pneumonia. Consequently, it may serve as an uncomplicated and useful diagnostic tool for clinicians to promptly and precisely ascertain the severity of psittacosis pneumonia, ultimately aiding them in devising the most optimal therapeutic plan.

Multiple infections secondary to immunosuppression after Chlamydia psittaci infection: a case report.

This study presents the clinical profile of a 74-year-old male patient admitted to the hospital due to a 20-day history of coughing, chest tightness, and dyspnea. Upon admission, the patient presented with fever, tachycardia, and tachypnea. Clinical examination revealed evidence of lung infection, sepsis, and multi-organ dysfunction, alongside abnormal blood gas analysis and elevated C-reactive protein (CRP) levels. Pathogen testing confirmed Chlamydia psittaci (C. psittaci), infection. Throughout the treatment course, the patient developed concurrent fungal and viral infections, necessitating a comprehensive approach involving combined antibiotic and antifungal therapy. Despite encountering treatment-related complications, the patient demonstrated clinical improvement with aggressive management. This case underscores the importance of recognizing immune suppression subsequent to Chlamydia infection, emphasizing the critical role of early diagnosis, intervention, and standardized treatment protocols in enhancing patient prognosis.

Chlamydia psittaci detected at a live poultry wholesale market in central China.

BACKGROUND: We investigated the presence of Chlamydia psittaci in poultry and the environment in live poultry wholesale markets in Changsha during 2021-2022 and conducted a phylogenetic analysis to understand its distribution in this market. METHODS: In total, 483 samples were analyzed using real-time polymerase chain reaction and 17 C. psittaci-positive samples using high-throughput sequencing, BLAST similarity, and phylogenetic analysis. RESULTS: Twenty-two out of 483 poultry and environmental samples were positive for C. psittaci (overall positivity rate: 4.55%) with no difference in positivity rates over 12 months. Chlamydia psittaci was detected at 11 sampling points (overall positivity rate: 27.5%), including chicken, duck, and pigeon/chicken/duck/goose shops, with pigeon shops having the highest positivity rate (46.67%). The highest positivity rates were found in sewage (12.5%), poultry fecal (7.43%), cage swab (6.59%), avian pharyngeal/cloacal swab (3.33%), and air (2.29%) samples. The ompA sequences were identified in two strains of C. psittaci, which were determined to bear genotype B using phylogenetic analysis. Thus, during monitoring, C. psittaci genotype B was detected in the poultry and environmental samples from the poultry wholesale market in Changsha. CONCLUSIONS: To address the potential zoonotic threat, C. psittaci monitoring programs in live poultry markets should be enhanced.

Reactive Oxygen Species Modulate Th17/Treg Balance in Chlamydia psittaci Pneumonia via NLRP3/IL-1ß/Caspase-1 Pathway Differentiation.

Chlamydia psittaci pneumonia (CPP) is a lung disease caused by the infection with the Chla-mydia psittaci bacterium, which can lead to severe acute respiratory distress syndrome and systemic symptoms. This study explored the specific mechanisms underlying the impact of reactive oxygen species (ROS) on the Th17/Treg balance in CPP. The levels of ROS and the differentiation ratio of Th17/Treg in the peripheral blood of healthy individuals and CPP patients were measured using ELISA and flow cytometry, respectively. The association between the ROS levels and Th17/Treg was assessed using Pearson correlation analysis. The ROS levels and the Th17/Treg ratio were measured in CD4+ T cells following H2O2 treatment and NLRP3 inhibition. The effects of H2O2 treatment and NLRP3 inhibition on the NLRP3/IL-1ß/caspase-1 pathway were observed using immunoblotting. Compared to the healthy group, the CPP group exhibited increased levels of ROS in the peripheral blood, an elevated ratio of Th17 differentiation, and a decreased ratio of Treg differentiation. ROS levels were positively correlated with the Th17 cell proportion but negatively correlated with the Treg cell proportion. The ROS levels and NLRP3/IL-1ß/caspase-1 expression were up-regulated in CD4+ T cells after H2O2 treatment. Furthermore, there was an increase in Th17 differentiation and a decrease in Treg differentiation. Conversely, the NLRP3/IL-1ß/caspase-1 pathway inhibition reversed the effects of H2O2 treatment, with no significant change in the ROS levels. ROS regulates the Th17/Treg balance in CPP, possibly through the NLRP3/IL-1ß/caspase-1 pathway. This study provides a new perspective on the development of immunotherapy for CPP.

Chlamydia psittaci Pneumonia: Diagnosis, Treatment, and Challenges in the Context of COVID-19.

BACKGROUND Rapid diagnosis is critical for effective treatment of severe pneumonia during the COVID-19 pandemic. Chlamydia psittaci, an atypical community-acquired pathogen, typically exhibits nonspecific clinical signs and requires stringent conditions for microbiological culture, complicating its identification. Metagenomic next-generation sequencing (mNGS), which involves shotgun sequencing of DNA or RNA from clinical samples, is a key technology in clinical settings. Although mNGS technology identifies nucleic acids, it should not be directly equated with the presence of pathogenic microorganisms. Nonetheless, it shows promise as a principal method for detecting atypical pathogens in severe infectious diseases in the future. CASE REPORT We present a case of severe community-acquired Chlamydia psittaci pneumonia, highlighting the ongoing mutations and frequent spread of COVID-19. The patient's severe pulmonary infection rapidly advanced, resulting in multiple organ failure, necessitating extracorporeal membrane oxygenation (ECMO) support. Despite initial inconclusive routine laboratory tests, diagnosis of Chlamydia psittaci pneumonia was confirmed through mNGS. Antibiotic treatment and multi-organ functional support were administered, leading to the patient's successful recovery and hospital discharge. CONCLUSIONS Diagnosing severe pneumonia caused by atypical pathogens amid the COVID-19 pandemic presents significant challenges. Initiating ECMO support without effective infection control poses considerable risks, such as increasing risk of catheter-related infections and antimicrobial treatment failure. In the case presented, mNGS proved instrumental in screening for atypical pathogens in critical infectious diseases. Application of multi-organ function support in reversible conditions affords clinicians time for pathogen identification and treatment, offering novel approaches for diagnosing and treating severe pneumonia induced by unconventional pathogens during epidemic outbreaks.

Chlamydia psittaci Screening of Animal Workers from Argentina Exposed to Carrier Birds.

Different syndromes are involved in human psittacosis (flu-like syndrome, atypical pneumonia up to lacrimal gland lymphoma). Diagnostic methods include serology, culture, and PCR. The rate of Chlamydia psittaci (Cp) positive tests among exposed workers is still unknown. Our study aimed to assess the rate of positive tests among workers who have contact with carrier birds in natural reserves from Buenos Aires, Argentina. Secondary aims were to analyze risk factors linked to these outcomes and the occurrence of signs that suggest psittacosis. Nasopharyngeal swabs and serum pairs were collected from employees who had interacted with confirmed carrier birds. Those with detectable DNA of Cp and/or anti-Chlamydia spp. antibody baseline titer ≥ 160 mUI/ml, or at least quadruplicating, were considered positive. Activities performed with or near birds, personal protective equipment use, and previous chronic conditions were assessed. Possible Cp-related pathologies were evaluated during follow-up. A total of 63 exposed workers (71.4% men) with a median age of 35.7 years (IQR 26-39) were evaluated to detect 28.6% positives. Respiratory chronic conditions were the unique factor associated with positive tests (OR 5.2 [1.5-18.5] p < .05). Surprisingly, about a third of the workers resulted positive and all responded to medical treatment, none developing an acute atypical pneumonia syndrome associated with classical presentation of psittacosis. Active testing for early diagnosis and proper treatment in zoological workers exposed to carrier or potentially carrier birds is strongly suggested as part of zoonotic diseases preventive measures.

Chlamydia psittaci-related pleuro-myocarditis.

Chlamydia psittaci ‒ related community-acquired pneumonia associated to acute myocarditis was diagnosed in a young man with no medical history, and a professional exposition to birds. The diagnosis was confirmed with positive specific polymerase chain reaction in bronchoalveolar lavage. The patient was treated with spiramycin for two weeks with anti-inflammatory treatment for myocarditis for three months. Clinical and biological improvement was rapidly observed followed by normalization of electrocardiogram and chest CT scan. No relapse was reported for over a two-year follow-up.

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.

Venous-arterial extracorporeal membrane oxygenation for psittacosis pneumonia complicated with cardiogenic shock: case report and literature review.

INTRODUCTION: Dilated cardiomyopathy (DCM) is characterized by the enlargement of the left ventricle or biventricular, accompanied by myocardial systolic dysfunction. Chlamydia psittacosis (CP) is a zoonotic pathogen, which can cause severe pneumonia, respiratory failure, and acute organ dysfunction. The deterioration of DCM caused by CP infection is extremely rare, and few cases of successful management were reported. CASE PRESENTATION: We reported a 67-year-old male patient with DCM and chronic heart failure. Who was admitted to ICU with severe pneumonia, acute hypoxemic respiratory failure, acute decompensated heart failure, arrhythmia, and cardiogenic shock. Mechanical ventilation (MV) and venous-arterial extracorporeal membrane oxygenation (VA-ECMO) were established for respiratory and circulatory support. Broncho alveolar lavage fluid(BALF)was collected for culture and metagenomics next-generation sequencing (mNGS) test. Repeated mNGS tests indicated the high possibility of CP pneumonia, thereafter, moxifloxacin and doxycycline were prescribed. After targeted antibiotics and organ support treatment, pneumonia, respiratory and circulatory failure were gradually resolved, patient was successfully weaned from MV and VA-ECMO. Finally, the patient was recovered and discharged alive. CONCLUSIONS: Severe respiratory and circulatory failure caused by CP infection in DCM patients is a rare life-threatening clinical condition. Early accurate diagnosis, targeted antibiotic therapy, coupled with extracorporeal life support posed positive impact on the patient's disease course and outcome.

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.

Chlamydia psittaci Pneumonia in a patient with motor neuron disease: a case report.

BACKGROUND: Motor neuron disease (MND) is a fatal neurodegenerative disorder that leads to progressive loss of motor neurons. Chlamydia psittaci (C. psittaci) is a rare etiology of community-acquired pneumonia characterized primarily by respiratory distress. We reported a case of C. psittaci pneumonia complicated with motor neuron disease (MND). CASE PRESENTATION: A 74-year-old male was referred to the Shaoxing Second Hospital at January, 2022 complaining of fever and fatigue for 2 days. The patient was diagnosed of MND with flail arm syndrome 1 year ago. The metagenomic next-generation sequencing (mNGS) of sputum obtained through bedside fiberoptic bronchoscopy showed C. psittaci infection. Then doxycycline was administrated and bedside fiberoptic bronchoscopy was performed to assist with sputum excretion. Computed Tomography (CT) and fiberoptic bronchoscopy revealed a significant decrease in sputum production. On day 24 after admission, the patient was discharged with slight dyspnea, limited exercise tolerance. One month later after discharge, the patient reported normal respiratory function, and chest CT showed significant absorption of sputum. CONCLUSIONS: The mNGS combined with bedside fiberoptic bronchoscopy could timely detect C. psittaci infection. Bedside fiberoptic bronchoscopy along with antibiotic therapy may be effective for C. psittaci treatment.

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.

Chlamydia psittaci: an emerging cause of equine abortion and fatal neonatal illness in south-eastern Australia.

While well known as a zoonotic pathogen of birds, Chlamydia psittaci is less well recognised as a cause of abortion in mares and severe infection in foals. However, in the past decade it has been causing epizootics of both in south-eastern Australia, as Charles El-Hage and James Gilkerson explain.

Epigenetic changes induced by pathogenic Chlamydia spp.

Chlamydia trachomatis, C. pneumoniae, and C. psittaci, the three Chlamydia species known to cause human disease, have been collectively linked to several pathologies, including conjunctivitis, trachoma, respiratory disease, acute and chronic urogenital infections and their complications, and psittacosis. In vitro, animal, and human studies also established additional correlations, such as between C. pneumoniae and atherosclerosis and between C. trachomatis and ovarian cancer. As part of their survival and pathogenesis strategies as obligate intracellular bacteria, Chlamydia spp. modulate all three major types of epigenetic changes, which include deoxyribonucleic acid (DNA) methylation, histone post-translational modifications, and microRNA-mediated gene silencing. Some of these epigenetic changes may be implicated in key aspects of pathogenesis, such as the ability of the Chlamydia spp. to induce epithelial-to-mesenchymal transition, interfere with DNA damage repair, suppress cholesterol efflux from infected macrophages, act as a co-factor in human papillomavirus (HPV)-mediated cervical cancer, prevent apoptosis, and preserve the integrity of mitochondrial networks in infected host cells. A better understanding of the individual and collective contribution of epigenetic changes to pathogenesis will enhance our knowledge about the biology of Chlamydia spp. and facilitate the development of novel therapies and biomarkers. Pathogenic Chlamydia spp. contribute to epigenetically-mediated gene expression changes in host cells by multiple mechanisms.

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.