Chlamydia psittaci (psittacosis) as a cause of community-acquired pneumonia: a systematic review and meta-analysis

Profile of Chlamydia vaccine research: A bibliometric analysis

Vaccination is the most effective measure to prevent Chlamydia infection. However, to date, no vaccine has successfully completed the rigorous clinical trial process and gained regulatory approval for use in clinical practice. Scholars have been working on a safe and effective Chlamydia vaccine. In order to better grasp, the global frontiers and development trends in this field, a comprehensive bibliometric analysis was carried out. A total of 234 publications closely regarding Chlamydia vaccines were culled from the Web of Science Core Collection database, and the bibliometric information was then extracted with CiteSpace and VOSviewer software. After measurement analysis, the most influential papers were identified in this area, including highly cited papers, references with strong citation burst, and high co-citated papers. Vaccine has published the most literature on Chlamydia vaccines. Only scholars from 39 countries/regions have been engaged in studying Chlamydia vaccines. The USA is the most prolific country and has the highest collaborative strength. The current research area has focused on protective immunity and immunopathological response. Major outer membrane protein (MOMP) is the most common target vaccine antigen. This study reveals the status of literature and highlights emerging trends in this field, which helps researchers seek insights into this area and serve as a reference guide for further investigations.

Early re-examination of chest CT may be unnecessary when patients with psittaci pneumonia at low and intermediate risk on Pneumonia Severity Index present with response to initial treatment

Background

Chlamydia parrot pneumonia (CPS) is a rare community-acquired pneumonia (CAP) caused by Chlamydia parrot infection. With the development of metagenomic second-generation sequencing technology (mNGS), its diagnostic rate has improved in recent years. However, there are few clinical studies on Chlamydia parrot pneumonia, especially for patients with low and intermediate pneumonia severity index (PSI), and the necessity of early review of chest computed tomography (CT) is not clear. This study aimed to explore the clinical significance of early review of chest CT in patients with low and intermediate risk of Chlamydia parrot pneumonia with PSI after initial treatment was effective.

Methods

Retrospective analysis of 8 patients with Chlamydia psittaci pneumonia diagnosed by metagenomic next-generation sequencing (mNGS) admitted to Zhejiang Provincial Tongde Hospital from January 2020 to December 2022 (PSI score ≤ 130 points). All patients had improved clinical symptoms and inflammatory markers after receiving antibiotic treatment, and chest CT was reexamined within 5-12 days. Evaluate the correlation between imaging changes before and after treatment and clinical symptoms and inflammatory indicators (CRP, PCT, WBC, etc.).

Results

After treatment, the patient's body temperature, CRP, PCT and other indicators decreased significantly (P < 0.05). However, early CT reexamination showed that imaging progressed in 5 cases (62.5%), was stable in 2 cases (25%), and only 1 case (12.5%) showed partial improvement (P > 0.05). Nevertheless, none of the patients had a deterioration in their condition later on and finally achieved imaging recovery. Clinicians did not adjust the treatment plan when imaging progressed, and only 1 case was given glucocorticoid additionally.

Conclusion

For patients with low- intermediate risk Chlamydia psittaci pneumonia with low PSI, if clinical symptoms and inflammatory markers improve, early reexamination of chest CT may have no additional clinical value and does not affect treatment decisions. Therefore, it is not recommended to routinely perform early CT re-examination for such patients to reduce unnecessary consumption of medical resources. Larger sample studies are needed in the future for further verification.

Clinical trial registration

https://www.medicalresearch.org.cn/login, identifier MR-33-25003507.

Global prevalence of psittacosis in outbreaks: a systematic review and meta-analysis

BACKGROUND

Psittacosis is a globally underappreciated and frequently undiagnosed zoonotic disease, and it is often difficult to determine the number of individuals exposed to Chlamydia psittaci. Despite numerous reported cases and outbreaks worldwide, there has been no systematic assessment of psittacosis prevalence to date, which is crucial for evaluating the disease burden and developing vaccines. Our objective is to evaluate the global prevalence of psittacosis in outbreaks.

METHODS

We conducted a comprehensive search across multiple databases, including PubMed, Web of Science, Cochrane Library, and Medline, from the date of establishment to May 15, 2024. Additionally, we manually searched reference lists of included articles and retrieved reviews to identify any supplementary articles. The primary summary data was the prevalence of psittacosis in the outbreaks. Pooled estimates of prevalence were calculated for both the entire population and subgroups using a random-effects model.

RESULTS

Thirty-one eligible studies from 13 countries across four continents were included in this review. The pooled prevalence of psittacosis among 4,158 exposed individuals in outbreaks was 27.7% (95% CI: 20.9-34.9). Meta-regression analysis of six potential influencing factors (geographic region, outbreak sites, outbreak season, infectious source, publication year, and study quality) indicated that the source of heterogeneity may be associated with the outbreak sites (P = 0.031). Furthermore, among the cases collected, the hospitalization rate was 42.3% (95% CI: 24.7-60.8), the prevalence of pneumonia was 59.7% (95% CI: 41.4-76.9), and the fatality rate was 1.8% (95% CI: 0-6.9).

CONCLUSIONS

The global prevalence of psittacosis in outbreaks was found to be 27.7%, with a hospitalization rate of 42.3%, a pneumonia rate of 59.7%, and a mortality rate of 1.8%. Such knowledge will assist governmental and medical authorities in formulating public health policies for populations at high risk of bird exposure, assessing the disease burden, and developing effective vaccines.

Clinical Characteristics of Five Cases of Chlamydia psittaci Pneumonia Diagnosed Using Metagenomics Next-Generation Sequencing

Objective: This study aimed to analyze the clinical characteristics of five cases of Chlamydia psittaci pneumonia diagnosed using metagenomics next-generation sequencing (mNGS) and to provide help for its diagnosis and treatment. Methods: Five patients who were admitted to the department of Respiratory and Critical Care Medicine of Beijing Aerospace General Hospital between June 2020 and December 2021 and diagnosed with C. psittaci pneumonia using mNGS were selected, including one case with severe pneumonia. We analyzed the clinical characteristics, epidemiology, laboratory results, treatment, and prognosis of the five participating patients. Results: The main clinical manifestations were high fever, dry cough, chest tightness, shortness of breath, and myalgia. All five patients had a history of contact with poultry. The white blood cell count was normal or slightly increased, the lymphocyte count was significantly decreased, and the percentage of neutrophil granulocyte, C-reactive protein (CRP), erythrocyte sedimentation rate, and procalcitonin were significantly increased. Chest computed tomography showed inflammatory infiltration and consolidation of one or more lung lobes, possibly accompanied by pleural effusion and liver function impairment. Bronchoscopy mainly showed congestion and edema of airway mucosa with less sputum in the airway. In all patients, we detected the nucleic acid sequences of C. psittaci in alveolar lavage fluid or sputum using mNGS and confirmed the diagnosis of C. psittaci pneumonia based on clinical manifestations and exposure history. After adjusting antibiotics to a moxifloxacin-based treatment regimen, the disease improved. The application of the mNGS assay enables us to make faster diagnoses of diseases so that timely medication can be administered, thus shortening the duration of a patient's illness. Conclusion: C. psittaci pneumonia has an acute onset, and fever and cough are common symptoms. A history of contact between the patient and birds is an important diagnostic clue; however, clinical symptoms and laboratory and imaging examinations lack specificity. The detection using mNGS of bronchoalveolar lavage fluid can quickly confirm the diagnosis and reduce missed diagnoses and misdiagnoses. Moxifloxacin-based therapy is effective, and patients require combination therapy if they have other bacterial infections.

Psittacosis pneumonia with the reversed halo sign: a case report and literature review

BACKGROUND

Chlamydia psittaci is a rare pathogen that causes community-acquired pneumonia. The reversed halo sign (RHS) is a computed tomography (CT) finding that is commonly observed in diseases such as cryptogenic organizing pneumonia, invasive fungal infections, tuberculosis, sarcoidosis, and pulmonary thromboembolism, but has seldom been described in association with psittacosis pneumonia.

CASE PRESENTATION

We report a case in which a 26-year-old man with a history of close contact with pigeons and chicken manure presented with fever and cough for 6 days. A CT examination revealed the RHS in the right lower lobe of the lung. Psittacosis pneumonia was diagnosed by metagenomic next-generation sequencing of the patient's bronchoalveolar lavage fluid. Treatment with omadacycline abolished his symptoms. We also discuss six other cases of psittacosis pneumonia with the RHS identified by literature search.

CONCLUSIONS

When clinicians encounter patients with atypical pneumonia with the RHS and a history of contact with poultry, psittacosis should be considered.

Psittacosis in Focus: A Review Addressing the Risks and Management Challenges in Outbreak Scenarios

Background and Aim

Psittacosis is a zoonotic disease that mostly affects birds and can infect people. It causes respiratory ailments that can be minor or severe. The disease's importance to public health is shown by the fact that it has been connected to isolated outbreaks in several parts of the world. Comprehending the hazards linked to psittacosis is crucial, given that epidemics may have extensive consequences for public health, especially in environments where people and birds interact closely. Therefore, examining the risks, challenges, and methods for overcoming psittacosis infections is the primary focus of the study.

Discussion

Psittacosis' principal dangers include severe respiratory problems, which are especially dangerous for vulnerable groups. Inadequate diagnostic goods and services, public ignorance, and variances in hospital infrastructure all pose challenges to effective management. Strategies for combating psittacosis must include improved monitoring and reporting systems, better access to diagnosis and treatment, and expanded public awareness on protection. Incorporating biosecurity strategies in flocks and agricultural operations is also critical to lowering transmission risk.

Conclusion

Prioritizing psittacosis control is imperative for global health regulatory organizations to prevent future outbreaks. To promote research, allocate funds, and support public health initiatives aimed at enhancing disease management, quick action is needed. By promoting international cooperation and enhancing healthcare systems, we can effectively address the problems caused by psittacosis and better safeguard populations everywhere from this preventable disease.

Epidemiological characteristics of human psittacosis in Guangzhou, China, January 2021 to June 2024

Background

Psittacosis is a global and underappreciated zoonosis, with increasing reported cases in many countries. There have been several outbreaks and even deaths of psittacosis reported in China. Understanding its epidemiological characteristics and dimensions is crucial for formulating precise prevention and control strategies. This study aimed to analyze the epidemiological characteristics of human psittacosis in Guangzhou, China.

Methods

The demographic characteristics, clinical manifestations, temporal patterns, geographic distribution and potential exposures of psittacosis in Guangzhou were analyzed based on the surveillance data and epidemiological investigation conducted between January 2021 and June 2024. Seasonal and trend decomposition using LOESS was applied to decompose the number of psittacosis cases into trend, seasonal and remainder component.

Results

A total of 148 cases were reported, with a significant increase in the number of psittacosis cases over the study period. Most of cases were sporadic and detected by metagenomic next-generation sequencing (mNGS). Psittacosis was predominant males aged 40-79 years. Fever and pneumonia were the most commonly observed clinical manifestations. A seasonal trend was observed in the number of psittacosis cases with a high prevalence of cases in December and March. A total of 108 local cases (87%) occurred in rural regions. Among local cases, 67.7% reported a history of contact with birds or poultry, and 17.7% had been exposed to a related environment. The suspected source of infection differed between urban and rural areas, with parrots being the primary source in urban areas and poultry in rural areas.

Conclusion

Increasing clinicians' awareness, enhancing epidemiological surveillance, paying close attention to the epidemic in rural areas, and implementing measures against avian influenza, will be conducive to preventing and controlling psittacosis.

COPB1-knockdown induced type I interferon signaling activation inhibits Chlamydia psittaci intracellular proliferation

Objective

Chlamydia psittaci is a zoonotic pathogen that causes an acute disease known as psittacosis. To establish infection in host cells, Chlamydia manipulates the host cell's membrane trafficking pathways.

Methods

In this study, using fluorescently labeled C. psittaci and screening a human membrane trafficking small interfering RNA (siRNA) library, we identified 34 host proteins that influenced C. psittaci infection in HeLa cells.

Results

Among these, knockdown (KD) of two genes encoding subunits of the coatomer complex I (COPI) inhibited the pathogen's intracellular survival. Specifically, the knockdown of COPB1, a COPI subunit, significantly reduced the intracellular proliferation of C. psittaci. Mechanistically, we found that type I interferon negatively affected C. psittaci infection. Moreover, COPB1 KD disrupted the homeostasis of STING, preventing its retrieval from the Golgi back to the endoplasmic reticulum (ER), which in turn activated type I interferon signaling.

Conclusion

Together, our findings advance the understanding of the mechanisms underlying Chlamydia infection and offer potential avenues for the development of new anti-C. psittaci strategies.

Clinical Characteristics and Predicting Disease Severity in Chlamydia psittaci Infection Based on Metagenomic Next-Generation Sequencing

Introduction

Psittacosis pneumonia, as a zoonotic infection, is induced by the pathogen Chlamydia psittaci. In the present study, we sought to characterize the clinical manifestations and prognosticate the severity of psittacosis pneumonia.

Methods

We retrospectively verified instances of psittacosis pneumonia in Zhejiang province, China, from January 2021 to April 2024. Relevant data pertaining to epidemiological, clinical, and laboratory aspects were compiled and evaluated.

Results

Among a total of 110 individuals enrolled who were diagnosed with psittacosis pneumonia, the median age being 62.0 years (IQR, 53-69 years). The most common comorbidities were hypertension (36.4%) and diabetes mellitus (17.3%). Patients categorized as having severe disease (n=68) were significantly older than those with mild disease (n=42). Most patients had notable elevations in aspartate aminotransferase (AST), creatine kinase (CK), creatine kinase-MB (CK-MB), lactate dehydrogenase (LDH), D-dimer, C-reactive protein (CRP), procalcitonin, total bilirubin (TBil), and interleukin-6, as along with significant reductions in lymphocytes, monocytes, albumin, and interleukin-4. Chest CT scans showed bilateral lung involvement in 70 cases. In the cohort of patients having received empirical antibiotic therapy, 57.3% had their antibacterial medication adjusted in light of the mNGS findings. mNGS results indicated that 31.8% (35/110) had suspected coinfections. The random forest classifiers based upon the clinical and laboratory characteristics attained AUC values of 0.822.

Discussion

The study underscores the efficacy of mNGS as a robust diagnostic tool for detecting Chlamydia psittaci, which can simultaneously detect other pathogens and guide clinical treatment. Severe patients exhibit significant inflammatory imbalances and lymphocyte depletion. A predictive model based on clinical and laboratory data at admission can effectively guide early clinical intervention.

Effectiveness of Omadacycline in a Patient with Chlamydia psittaci and KPC-Producing Gram-Negative Bacteria Infection

Chlamydia psittaci is one of the primary pathogens responsible for community-acquired atypical pneumonia. If not treated promptly, it can progress to severe pneumonia and may lead to multiple organ dysfunction as well as secondary infections with multi-drug-resistant (MDR) bacteria. Omadacycline, a novel aminomethylcycline antibiotic derived from tetracycline, exhibits high activity against various bacterial strains. This case report describes a patient who developed severe pneumonia caused by Chlamydia psittaci in conjunction with a MDR bacterial infection. Despite initial treatment with moxifloxacin and doxycycline, the patient experienced treatment failure. The patient's condition deteriorated, presenting complications such as progressive infection, leukopenia, liver dysfunction, electrolyte imbalances, and respiratory alkalosis. Following the adjustment to omadacycline therapy for 48 hours, all complications were rapidly alleviated, leading to successful treatment of the patient.

Clinical features and prognostic predictors of C. Psittaci Pneumonia: a systematic review and individual patient meta-analysis

BACKGROUND

The clinical presentations and prognostic indicators of C. psittaci pneumonia are inadequately investigated currently. The objective of the study was to assess the clinical presentation of C. psittaci pneumonia and the risk factors for severe pneumonia, within a systematic review and individual patient meta-analysis.

METHODS

We searched PubMed, CNKI, and Wanfang databases for case reports/series of proven/probable psittacosis published between 1st January 2000 and 28th February 2023, including all hospitalized individuals aged ≥ 18 years. Patient demographics, manifestations, diagnostic methods, and outcomes were summarized descriptively. Patients were divided into severe or non-severe pneumonia groups mainly according to the ATS/IDSA 2007 criteria. Prognostic predictors for severe C. psittaci pneumonia were identified using multivariate logistic regression.

RESULTS

3062 articles of 196 (566 individual patient cases) were included in the final analysis. Patients with chronic cardiovascular disease face a significantly elevated risk of developing severe C. psittaci pneumonia (adjusted odds ratio (aOR) 2.63; 95% confidence interval (CI) 1.05-6.59; P = 0.039). Symptoms including dyspnea (aOR 4.88; 95% CI 3.19-7.46; P < 0.001), neuropsychiatric symptoms (aOR 3.58; 95% CI 2.05-6.28; P < 0.001), gastrointestinal symptoms (aOR 1.76; 95% CI 1.10-2.80; P = 0.018), or the presence of multilobar infiltrates on imaging (aOR 3.27; 95% CI 2.11-5.06; P < 0.001) upon admission frequently serve as indicators of severe pneumonia.

CONCLUSIONS

Chronic cardiovascular disease increases susceptibility to severe C. psittaci pneumonia. The presence of dyspnea, neuropsychiatric symptoms, gastrointestinal symptoms, and multilobar infiltrates upon admission merits clinicians' attention, advocating for timely sample submission for metagenomic next-generation sequencing (mNGS) to ascertain the etiology.

Chlamydia psittaci pneumonia - evolutionary aspects on chest CT

PURPOSE

To present the different findings of Chlamydia psittaci (C. psittaci) pneumonia on computed tomography (CT) according to the progression of the disease, to improve diagnostic accuracy, guide early clinical diagnosis, evaluate treatment efficacy, and reduce the mortality associated with the disease.

METHODS

In total, 80 cases of C. psittaci pneumonia diagnosed through next-generation sequencing from January 2019 to December 2023 in multiple hospitals in China were collected according to the inclusion criteria and analyzed. The study discussed important CT findings and their dynamic changes.

RESULTS

The most common manifestations of C. psittaci pneumonia are lobar pneumonia and spherical pneumonia types with interstitial changes. The most common signs are the intralobular lines, air bronchogram sign, and reverse halo sign. In addition, necrosis, cavitation, and the tree-in-bud sign are rare but often associated with pleural effusion and splenomegaly. In the ultra-early stage, vascular inflammation changes were observed on imaging, often manifesting as ground-glass opacities around small core vessels or thickening of pulmonary hilar vessels. In the early stage, secondary lobules showed high-density shadows, which rapidly fused into large areas in the progressive stage, easily forming lobar pneumonia. The repair and absorption period tended to show the formation of the reverse halo sign centrally, and the dissipation period might have led to the formation of fibrous bands.

CONCLUSION

Combining clinical manifestations, laboratory tests, contact history, and imaging findings contribute to the diagnosis of C. psittaci pneumonia.

Psittacosis Pneumonia Features, Distinguishing Characteristics, and Outcomes: A Retrospective Study

Purpose

Psittacosis is an often-neglected cause of community acquired pneumonia (CAP). The limited diagnostic methods for psittacosis pneumonia invariably result in an unfavourable prognosis. Consequently, the early detection of psittacosis pneumonia is crucial. This study aimed to analyse the characteristics, clinical features and treatments of the patients to improve early diagnosis and outcomes.

Patients and Methods

We retrospectively analyzed the clinical features and outcomes of 52 cases of psittacosis pneumonia diagnosed with next-generation sequencing (NGS) from January 2022 to August 2024 in a local tertiary hospital in China.

Results

Of the 52 patients, 18 had a clear exposure to poultry or birds. The main clinical manifestations included fever (100%, 52/52), cough (75.0%, 39/52), fatigue (57.7%, 30/352), and dyspnea (36.5%, 19/52). Significant elevations in neutrophil counts (NEUT), C-reactive protein (CRP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), D-dimer, lactate dehydrogenase (LDH), creatine kinase (CK), interleukin-6 (IL-6) and interferon-γ (IFN-γ), as well as reductions in lymphocyte (LY) and albumin (ALB) were observed. The main chest computed tomography (CT) features were consolidated. Eight patients diagnosed with severe CAP (SCAP) exhibited higher NEUT, CRP, procalcitonin (PCT), blood urea nitrogen (BUN), creatinine, D-Dimer and IL-6 levels, as well as lower oxygen index. The interval between the onset of symptoms and diagnosis was 6-34 days. C. psittaci infection was identified by metagenomic NGS (mNGS) or targeted NGS (tNGS) in all cases, and the average length of hospital stay for these patients was 9.4 days. Following the identification of the aetiology, all patients were promptly initiated on tetracycline- or fluoroquinolone-based therapy, with complete recovery observed in all cases.

Conclusion

Patients exposed to poultry should be alert to Chlamydia psittaci pneumonia. The application of NGS has improved the diagnostic accuracy of C. psittaci pneumonia, reduced unnecessary use of antibiotics, and shortened the course of disease. Patients who received tetracycline-based therapy showed a good prognosis.

Acute respiratory distress syndrome caused by Chlamydia psittaci: a case report and literature review

Background

Psittacosis is a zoonotic disease with a low incidence rate and a lack of specificity in clinical manifestations, making it prone to be missed, misdiagnosed, and even cause delayed treatment for patients. Metagenomic next-generation sequencing (mNGS) was successfully performed for the diagnosis of a young patient with psittacosis progressing to acute respiratory distress syndrome (ARDS), and precisely targeted antibiotic treatment was promptly administered. Additionally, a comprehensive review was conducted on 68 cases of psittacosis complicated with ARDS, with the goal of improving the clinical awareness of this disease.

Case presentation

This study reports a 37-year-old young female who was infected with Chlamydia psittaci (C. psittaci) after contact with parrots and eventually developed ARDS. The patient initially developed fever and sore throat, followed by cough and expectoration. Despite receiving empirical anti-infection treatment, the condition continued to progress rapidly, and severe dyspnea developed within a short period of time. She was subsequently transferred to the intensive care unit (ICU) and underwent tracheal intubation and mechanical ventilation due to acute respiratory failure. After the DNA sequence of C. psittaci in bronchoalveolar lavage fluid (BALF) was detected through mNGS, the patient received targeted antibiotic treatment with doxycycline and moxifloxacin, and her clinical symptoms gradually improved.

Conclusion

Epidemiological investigations and the application of mNGS are crucial for the early identification and diagnosis of psittacosis. For suspected psittacosis patients, the application of mNGS technology could promote early identification of pathogens and targeted antimicrobial therapy, which might improve patient prognosis. In addition, young psittacosis patients without underlying disease should also be vigilant about the possibility of developing severe cases.

Chlamydia psittaci: A zoonotic pathogen causing avian chlamydiosis and psittacosis

Chlamydia psittaci is an obligate intracellular gram-negative bacterium with a unique biphasic developmental cycle. It is a zoonotic pathogen with a wide range of hosts and can cause avian chlamydiosis in birds and psittacosis in humans. The pathogen is transmitted mainly through horizontal transmission between birds. Cross-species transmission sometimes occurs and human-to-human transmission has recently been confirmed. This review provides an updated overview of C. psittaci from the perspective of both avian chlamydiosis and psittacosis. We include the aspects of genotype, host-pathogen interaction, transmission, epidemiology, detection and diagnosis, clinical manifestation, management, and prevention, aiming to provide a basic understanding of C. psittaci and offer fresh insights focused on zoonosis and cross-species transmission.

Distinction of clinical features and microbiological methods between Chlamydia psittaci and Legionella pneumophila pneumonia confirmed by metagenomic next-generation sequencing

OBJECTIVES

Detection and diagnosis of Chlamydia psittaci (C. psittaci) pneumonia is often overlooked due to conventional methods limitations and similarity to other atypical community acquired pneumonia (CAP). Using mNGS, we aimed to distinguish psittacosis from legionellosis for early C. psittaci pneumonia diagnosis and better prognosis.

METHODS

Thirty-seven patients diagnosed with atypical CAP were enrolled in this retrospective study, including 14 C. psittaci pneumonia and 23 Legionella pneumophila (L. pneumophila) pneumonia. We collected and compared baseline, lab results, radiology imaging, conventional microbiological methods and more importantly, mNGS results of clinical samples, as well as the treatments and prognosis between psittacosis and legionellosis.

RESULTS

Patients with C. psittaci and L. pneumophila had similar symptoms and were presented with high levels of inflammatory markers. However, patients with C. psittaci pneumonia were more likely to have exposure to birds or parrots [11 (78.6%) vs. 2 (8.7%), p < 0.001], had higher proportions of fever and chill (p = 0.015 and 0.035), higher levels of hemoglobin and albumin (p = 0.002 and 0.018) compared with those with L. pneumophila. Of 14 C. psittaci patients, only one had positive IgM antibody, with no positive cultures. Early identification of pathogens by mNGS method contributed to timely antibiotics' adjustment and better outcomes then, yet with similar hospital mortality between two groups [7.1% (1/14) vs. 34.8% (8/23), p = 0.112].

CONCLUSION

Early mNGS detection of atypical pathogens in multiple samples improves on traditional methods, promptly adjust empirical antimicrobial treatment to pathogen-targeted antibiotics, further improve prognosis.

Early and rapid diagnosis of Chlamydia psittaci pneumonia by tNGS in six patients: a case series

Background

Psittacosis is a zoonotic infectious disease caused by Chlamydia psittaci (C. psittaci) infection, which can be transmitted by birds, poultry and wild animals. The symptoms and imaging findings of C. psittaci pneumonia are atypical and primarily rely on etiological diagnosis. The incidence of C. psittaci infection has been significantly underestimated because of the low sensitivity and poor timeliness of traditional diagnostic methods. Therefore, early and accurate diagnosis of psittacosis remains a challenge.

Case presentation

A case series with six pneumonia patients who were admitted to our hospital in the period from January 2023 to June 2023 is presented. These patients exhibited acute onset and symptoms, including fever, cough, poor appetite, dry mouth, dizziness, chills, and chest tightness. Despite comprehensive laboratory and radiological examinations, the cause of the pneumonia remained unidentified. Therefore, a sample of bronchoalveolar lavage fluid (BALF) was tested via target next-generation sequencing (tNGS), which revealed a positive result for C. psittaci. Prompt adjustment of the treatment regimens upon identification of the pathogen led to favorable outcomes in all patients.

Conclusion

tNGS is a novel diagnostic technology that enables rapid, accurate and cost-effective detection of C. psittaci pneumonia. Early detection of C. psittaci can improve patient outcomes through timely adjustment of therapies.

Hearing loss as the first symptom of pneumonia caused by Chlamydia psittaci: a case report and literature review

BACKGROUND

The typical clinical symptoms of psittacosis pneumonia include fever, dry cough, and chills. Sudden sensorineural hearing loss is a relatively uncommon condition in pneumonia caused by Chlamydia psittaci. In this study, we reported a rare case of Chlamydia psittaci pneumonia presented as hearing loss.

CASE PRESENTATION

A 65-year-old man presented to our hospital with sudden hearing loss, cough with sputum, and fever for the last three days. Chest computed tomography revealed inflammation of the left lung and poor response to broad-spectrum antibiotics. The metagenomic next-generation sequencing (mNGS) of bronchoalveolar lavage fluid identified the sequence of Chlamydia psittaci. Subsequently, antibiotic treatment was adjusted to doxycycline hydrochloride and moxifloxacin, resulting in significant improvement in both hearing loss and lung infection.

CONCLUSIONS

Sudden sensorineural hearing loss as an extrapulmonary feature of Chlamydia psittaci pneumonia is extremely rare. Although the exact mechanism remains unclear, this case report described a patient with sudden bilateral sensorineural hearing loss as a presenting feature of Chlamydia psittaci pneumonia, illustrating the importance of the extrapulmonary features of atypical pneumonia. The mNGS test could provide early diagnosis. Many patients had a good prognosis with prompt and effective treatment.

A case of severe psittacosis pneumonia complicated by splenic infarction

CLINICAL DATA

Chlamydia psittaci pneumonia is a community-acquired pneumonia caused by Chlamydia psittaci. While severe cases may lead to critical conditions such as respiratory failure, splenic infarction is relatively uncommon. A severe patient with Chlamydia psittaci pneumonia admitted to our hospital experienced a splenic infarction during treatment. Fortunately, the patient's situation was improved after careful treatment. Now, the patient has been discharged. Further exploration of the mechanism of concurrent splenic infarction is required.

BACKGROUD

Psittacosis pneumonia, a zoonotic infectious disease transmitted from birds to humans, is caused by Chlamydia psittaci and represents a type of chlamydial pneumonia [1]. Insome instances, the disease may progress to severe pneumonia and respiratory failure, necessitating intensive support measures, including mechanical ventilation. The advent of technologies such as Metagenomic Next-Generation Sequencing (mNGS) for the etiological diagnosis of infectious diseases [2] has improved the diagnostic and treatment success rates for Psittacosis. Instances of severe chlamydial pneumonia with complications such as splenic infarction are uncommon. A patient with severe Psittacosis pneumonia complicated by splenic infarction was admitted to the Emergency Intensive Care Unit (EICU) of Haining People's Hospital and subsequently improved following effective anti-infective and anticoagulant therapy. This report is provided herein.

Comparison of clinical, laboratory and radiological characteristics between COVID-19 and Chlamydia psittaci pneumonia: a multicenter retrospective study

Chlamydia psittaci pneumonia (CPP) exhibits similar characteristics as of COVID-19 with respect to clustering outbreaks and onset symptoms. This study is aimed at exploring the different clinical manifestations of both pneumonias to establish a simple nomogram to distinguish them. This multicenter, retrospective, case-control study compared two independent cohorts of patients with CPP or COVID-19. The risk factors of CPP were analyzed using multivariate logistic regression, which was used to establish the nomogram. Both patients with CPP and COVID-19 exhibited similar clinical symptoms. As compared to patients with COVID-19, a higher proportion of patients with CPP had nervous system symptoms. Patients with CPP had higher inflammatory indicators, creatine kinase, and lower lymphocyte and albumin. They also had lower proportions of ground-glass opacity and bilateral lung involvement than COVID-19 patients. Furthermore, patients with CPP had higher 30 day mortality as well as higher rates of severe pneumonia, septic shock, and ICU admission. Multivariate logistic regression showed that nervous system symptoms, lymphocytes, creatine kinase, bilateral lung lesions, and ground-glass opacity were risk factors for CPP. Incorporating these five factors, the nomogram achieved good concordance index of 0.989 in differentiating CPP from COVID-19, and had well-fitted calibration curves. Despite similar clinical characteristics, nervous system symptoms, lymphocyte, creatine kinase, lesions in bilateral lungs, and ground-glass opacity may help in differentiating the pneumonias. These were combined into a clinically useful nomogram for rapid and early identification of CPP to avoid misdiagnosis and help in the decision-making process.

Clinical Features and a Prediction Model for Early Prediction of Composite Outcome in Chlamydia psittaci Pneumonia: A Multi-Centre Retrospective Study in China

Introduction

C. psittaci pneumonia has atypical clinical manifestations and is often ignored by clinicians. This study analyzed the clinical characteristics, explored the risk factors for composite outcome and established a prediction model for early prediction of composite outcome among C. psittaci pneumonia patients.

Methods

A multicenter, retrospective, observational cohort study was conducted in ten Chinese tertiary hospitals. Patients diagnosed with C. psittaci pneumonia were included, and their clinical data were collected and analyzed. The composite outcome of C. psittaci pneumonia included death during hospitalization, ICU admission, and mechanical ventilation. Univariate and multivariable logistic regression analyses were conducted to determine the significant variables. A ten-fold cross-validation was performed to internally validate the model. The model performance was evaluated using various methods, including receiver operating characteristics (ROC), C-index, sensitivity, specificity, positive/negative predictive value (PPV/NPV), decision curve analysis (DCA), and clinical impact curve analysis (CICA).

Results

In total, 83 patients comprised training cohorts and 36 patients comprised validation cohorts. CURB-65 was used to establish predictive Model 1. Multivariate logistic regression analysis identified three independent prognostic factors, including serum albumin, CURB-65, and white blood cells. These factors were employed to construct model 2. Model 2 had acceptable discrimination (AUC of 0.898 and 0.825 for the training and validation sets, respectively) and robust internal validity. The specificity, sensitivity, NPV, and PPV for predicting composite outcome in the nomogram model were 91.7%, 84.5%, 50.0%, and 98.4% in the training sets, and 100.0%, 64.7%, 14.2%, and 100.0% in the validation sets. DCA and CICA showed that the nomogram model was clinically practical.

Conclusion

This study constructs a refined nomogram model for predicting the composite outcome in C. psittaci pneumonia patients. This nomogram model enables early and accurate C. psittaci pneumonia patients' evaluation, which may improve clinical outcomes.

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.

Chlamydia in pigs: intriguing bacteria associated with sub-clinical carriage and clinical disease, and with zoonotic potential

Chlamydiae are bacteria that are intriguing and important at the same time. The genus Chlamydia encompasses many species of obligate intracellular organisms: they can multiply only inside the cells of their host organism. Many, perhaps most animals have their own specifically adapted chlamydial species. In humans, the clinically most relevant species is Chlamydia trachomatis, which has particular importance as an agent of sexually transmitted disease. Pigs are the natural host of Chlamydia suis but may also carry Chlamydia abortus and Chlamydia pecorum. C. abortus and possibly C. suis have anthropozoonotic potential, which makes them interesting to human medicine, but all three species bring a substantial burden of disease to pigs. The recent availability of genomic sequence comparisons suggests adaptation of chlamydial species to their respective hosts. In cell biological terms, many aspects of all the species seem similar but non-identical: the bacteria mostly replicate within epithelial cells; they are taken up by the host cell in an endosome that they customize to generate a cytosolic vacuole; they have to evade cellular defences and have to organize nutrient transport to the vacuole; finally, they have to organize their release to be able to infect the next cell or the next host. What appears to be very difficult and challenging to achieve, is in fact a greatly successful style of parasitism. I will here attempt to cover some of the aspects of the infection biology of Chlamydia, from cell biology to immune defence, epidemiology and possibilities of prevention. I will discuss the pig as a host species and the species known to infect pigs but will in particular draw on the more detailed knowledge that we have on species that infect especially humans.

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.

Clinical diagnosis and treatment of seven patients diagnosed pneumonia caused by Chlamydia abortus: a case series report

Background

Chlamydia abortus pneumonia is very rare in normal people. At present, there is a lack of clinical data on the clinical characteristics and diagnosis and treatment experience of patients with this type of infection. Our team had recently treated 7 cases of these patients. This study aims to comprehensively summarize and analyze the clinical characteristics and treatment methods of Chlamydia abortus pneumonia, and to provide clinical evidence for the diagnosis and treatment of Chlamydia abortus pneumonia.

Methods

Clinical data were retrospectively collected from patients diagnosed with Chlamydia abortus pneumonia through metagenomic next-generation sequencing (mNGS) at the Department of Pulmonary and Critical Care Medicine, Meizhou People's Hospital.

Results

Seven patients with Chlamydia abortus pneumonia reported a history of poultry exposure, experiencing fever alongside respiratory or digestive symptoms. Marked elevation of blood inflammation markers, accompanied by hypoproteinemia and liver damage, was observed. Chest CT scans revealed pneumonia and pleural effusion. Chlamydia abortus was detected in blood or bronchoalveolar lavage fluid (BALF) through mNGS, often co-occurring with Chlamydia psittaci or other bacteria infections. Notably, Doxycycline demonstrated efficacy in treating Chlamydia abortus.

Conclusion

Chlamydia abortus infection is a zoonotic disease, particularly among individuals with a history of poultry exposure, and mNGS emerges as a reliable diagnostic tool for its detection. Chlamydia abortus infection manifests with systemic and lung inflammation, effectively addressed through Doxycycline therapy.

Type B3 thymoma complicated with Chlamydia psittaci pneumonia with rare features: A case report

The case of a patient with type B3 thymomacomorbid with Chlamydia psittaci (C. psittaci) pneumonia exhibiting rare features is presented in the current report. The patient was admitted at the Second Affiliated Hospital of Jiaxing University (Jiaxing, China) with a history of direct contact with poultry. Clinical manifestations included fever, shivers, cough, fatigue and poor appetite. Chest computed tomography (CT) indicated right lung pneumonia, while metagenomics next-generation sequencing using bronchoalveolar lavage fluid confirmed infection with C. psittaci. Additionally, positron emission tomography-CT suggested the presence of thymoma. After surgery and treatment with doxycycline and imipenem cilastatin, the patient was discharged showing signs of improvement.

Challenges in Chlamydial Serology: Insights from a Belgian and a Dutch Population Cohort

Serology routinely serves as a diagnostic tool to confirm Chlamydia infections in humans. Particularly in delayed settings, such as post-outbreak scenarios where the acute phase of infection has subsided, serology is invaluable. Multiple studies, nonetheless, indicate deficiencies in specificity and sensitivity of current chlamydial antibody detection assays. Incorporation of multiple antigens per target is known to improve the accuracy of chlamydial serological assays. We, therefore, used the recomLine test (Mikrogen diagnostics) on serological samples of two cohorts, as it is the only commercially available test allowing detection of antibodies against three human pathogenic Chlamydia species (C. trachomatis, C. pneumoniae and C. psittaci) using multiple antigens per target. The first cohort (n = 156; samples collected between 2008 and 2022 during a C. trachomatis screening initiative) comprised women from the Netherlands (NL) with past exposure to C. trachomatis, while the second cohort (n = 44; samples collected in 2018 in a health examination survey) consisted of Belgian citizens (BE) with occupational or recreational exposure to chickens, representing a risk population for C. psittaci. The test indicated a statistically equivalent C. pneumoniae seroprevalence in both cohorts (39.10% in NL and 34.09% in BE; p = 0.337). As expected C. trachomatis seroprevalence was significantly higher (p < 0.001) in the Dutch cohort (48.72%), as compared to the Belgian cohort (4.55%). Lastly, C. psittaci seroprevalence did not significantly differ between the two groups (2.27% in BE and 1.92% in NL; p = 0.633), even though a higher prevalence was expected for the Belgian cohort. This prompts us to question whether the Belgian cohort truly constituted a C. psittaci risk population or whether the recomLine test is susceptible to cross-reaction of species-specific antibodies, thereby increasing C. psittaci prevalence in the Dutch cohort. We advocate for the development of affordable, highly sensitive antibody detection assays that can effectively distinguish between chlamydial species, addressing the increasing demand for enhanced serological testing methodologies.

Pneumonia Caused by Chlamydia psittaci and SARS-CoV-2 Coinfection Diagnosed Using Metagenomic Next-Generation Sequencing: A Case Report

We report a case of pneumonia caused by coinfection with Chlamydia psittaci and the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron XBB.1 variant, confirmed using metagenomic next-generation sequencing (mNGS) and quantitative polymerase chain reaction (qPCR). C. psittaci and SARS-CoV-2 were detected in bronchoalveolar lavage fluid using mNGS. Additionally, mNGS detected C. psittaci in blood and nasopharyngeal specimens and was more sensitive than qPCR. The patient recovered after treatment with moxifloxacin. This report highlights the use of coinfections of C. psittaci and SARS-CoV-2, as mNGS has already been recognized to be a diagnostic tool for identifying coinfections.

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.

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.

The serodiagnositic value of Chlamydia trachomatis antigens in antibody detection using luciferase immunosorbent assay

Introduction

Among the different antigens used in the detection of anti-Chlamydia trachomatis antibodies, significant differences in sensitivity and specificity have been observed. Further evaluation of C. trachomatis antigens in antibody detection is urgently needed for the development and application of C. trachomatis serologic assays.

Methods

Chlamydia trachomatis antigens Pgp3, TmeA, InaC, and HSP60 were selected and used in luciferase immunosorbent assay (LISA). The detection results obtained from well-defined C. trachomatis positive and negative samples were compared with the commercial C. trachomatis ELISA (Mikrogen) for performance evaluation.

Results

Pgp3, TmeA, InaC, and HSP60-based LISA showed sensitivity of 92.8, 88.8, 90.4, and 94.4%, and specificity of 99.2, 99.2, 99.2, and 92%, respectively. ROC analysis indicated that Pgp3-based LISA showed similar performance to Mikrogen ELISA (AUC 0.986 vs. 0.993, p = 0.207). Furthermore, four C. trachomatis antigens achieved strong diagnostic efficiency, i.e., positive likelihood ratios [+LR] ≥ 10 in C. trachomatis-infected women and negative likelihood ratios [-LR] ≤ 0.1 in C. trachomatis negative low exposure risk children, but only Pgp3 and TmeA showed strong diagnostic value in general adults. In addition, Pgp3, TmeA, and InaC, but not HSP60, achieved high performance, i.e., both positive predictive value (PPV) and negative predictive value (NPV) ≥ 90.9%, and showed no significant cross-reactivity with anti-Chlamydiapneumoniae.

Conclusion

Three C. trachomatis species-specific antigens Pgp3, TmeA, and InaC show superior performance in the detection of anti-C. trachomatis antibody, indicating the potential to be used in developing C. trachomatis serologic tests.

Clinical Characteristics of Chlamydia psittaci Infection Diagnosed by Metagenomic Next-Generation Sequencing: A Retrospective Multi-Center Study in Fujian, China

Objective

This study aimed to describe and compare the epidemiological, demographic, clinical, laboratory and radiological characteristics as well as the complications, treatments, and outcomes of these patients.

Methods

We retrospectively investigated clinical data of patients with C. psittaci infection (psittacosis) in eight Grade IIIA hospitals of Fujian. Metagenomic next-generation sequencing (mNGS) was used identify C. psittaci in clinical samples of all included patients.

Results

A total of 74 patients (39 severe/35 non-severe) was diagnosed with psittacosis, 25 (33.8%) of whom had history of poultry exposure. Common symptoms included high fever (98% [37/74]), fatigue (52.7% [39/74]), and dyspnea (51.4% [38/74]). Common manifestations in imaging included consolidation (89.2%), pleural effusion (77.0%), and air bronchogram (66.2%). Common complications included acute respiratory distress syndrome (55.4% [41/74]), type I respiratory failure (52.7% [39/74]), acute liver injury (41.9% [31/74]), and secondary infection (27.0% [20/74]). The in-hospital mortality rate was 8.11% (6/74).

Conclusion

C. psittaci infection is represents an underestimated cause of CAP. For SCAP patients with poultry and bird contact history, specimens were encouraged to be sended for mNGS test in time. C. psittaci infection can lead to severe, multiple system involvement, and several complications. mNGS facilitate timely diagnosis of C. psittaci infection.

Zoonotic and other veterinary chlamydiae - an update, the role of the plasmid and plasmid-mediated transformation

The obligate intracellular bacterial genus Chlamydia harbours species with zoonotic potential, particularly C. psittaci, causative agent of psittacosis, and C. abortus, which may lead to miscarriage in pregnant women. The impact of other bird chlamydiae such as C. avium, C. gallinaceae, and C. buteonis, or reptilian species such as C. crocodili, amongst others, on human health is unclear. The chlamydial native plasmid, a suspected virulence factor, is present in all currently described 14 Chlamydia species except for some plasmid-free strains. The plasmid is also the primary tool to study chlamydial genetics, a still developing field that has mostly focused on C. trachomatis. Only recently, genetic transformation of C. felis, C. pecorum, C. pneumoniae, C. psittaci, and C. suis has succeeded, but existing methods have yet to be refined. In this review article, we will provide an update on the recent developments concerning the zoonotic potential of chlamydiae. Furthermore, we present an overview about the current state of knowledge regarding the chlamydial plasmid in terms of prevalence and significance as a virulence factor. Finally, we give insights into the progress of developing genetic tools for chlamydial species other than C. trachomatis with a special focus on zoonotic and veterinary chlamydiae.

Omadacycline for the Treatment of Severe Chlamydia psittaci Pneumonia Complicated with Guillain-Barre Syndrome

Background

Chlamydia psittaci (C. psittaci) is a pathogen that is seldom implicated in community-acquired pneumonia and is rarely linked to severe pneumonia. Reports of severe C. psittaci pneumonia accompanied by Guillain-Barre syndrome (GBS) are scarce. Tetracyclines are the preferred therapeutic approach for psittacosis. Omadacycline, a novel tetracycline, demonstrates strong antibacterial efficacy against typical bacteria and atypical pathogens, including C. psittaci. However, its application in the treatment of psittacosis pneumonia remains constrained.

Case Presentation

A 77-year-old female patient was admitted to the hospital presenting with symptoms of fever, low back pain, and headache. The diagnosis of C. psittaci was established through the utilization of metagenomic next-generation sequencing (mNGS). Initial administration of moxifloxacin, meropenem, piperacillin-tazobactam, and doxycycline proved to be ineffective. Subsequent omadacycline leaded to the successful resolution of fever and dyspnea. However, after the endotracheal tube was removed, the patient experienced a rapid decline in symmetrical limb strength, leading to a diagnosis of GBS based on clinical manifestations, cerebrospinal fluid analysis, and electromyography. Following a 5-day course of immunoglobulin therapy and nutritional nerve treatment, the patient's condition ameliorated, culminating in an uncomplicated discharge.

Conclusion

This case provides evidence supporting the potential use of omadacycline as a therapeutic option for the treatment of severe C. psittaci pneumonia. The utilization of mNGS technology is of paramount importance in the prompt identification of uncommon pathogens, including C. psittaci. Nevertheless, the occurrence of GBS should be taken into consideration when C. psittaci pneumonia is accompanied by symmetrical limb weakness. These findings have important implications for the diagnosis, treatment, and management of patients with C. psittaci pneumonia.

Clinical features and risk factors of liver injury in patients with Chlamydia psittaci pneumonia- a retrospective analysis

Background

Research into the effects of Chlamydia psittaci pneumonia on the liver has emerged in the last few years. However, no studies have systematically described liver injury in patients with psittacosis. We present the first report on the clinical features and risk factors of liver injury in patients with Chlamydia psittaci pneumonia.

Methods

We retrospectively collected the clinical parameters for 46 patients with Chlamydia psittaci pneumonia admitted to Jinhua Central Hospital from January 2019 to February 2023. We analyzed the liver function parameters and summarized the clinical characteristics and risk factors of liver injury.

Results

Among the 46 patients, 39 (84.8%) had abnormal liver function, and 23 (50.0%) had liver injury. The ratio of patients with a history of alcohol consumption (39.1% vs. 4.3%, P =0.004) or severe pneumonia (56.5% vs. 26.1%, P =0.036) was higher in the liver injury group compared with the non-liver injury group. Laboratory tests showed higher lactate dehydrogenase (LDH) levels in the liver injury group (P <0.001). The optimal cut-off LDH level associated with liver injury was 473 IU/L as determined by ROC curve analysis. Furthermore, multivariate logistic regression analysis demonstrated that a history of alcohol consumption (odds ratio [OR] = 11.251; 95% confidence interval [CI] = 1.022 ~ 123.897, P =0.048) and an LDH level of ≥ 473IU/L (OR = 11.635, 95% CI = 1.832 ~ 73.869, P =0.009) were independent risk factors for liver injury.

Conclusions

A history of alcohol consumption and an LDH level of over 473 IU/L are independent risk factors for Chlamydia psittaci pneumonia-related liver injury. It is recommended that particular attention be given to monitoring and evaluating liver function parameters when treating patients with Chlamydia psittaci pneumonia who have a high LDH level and history of alcohol consumption.

Omadacycline for the treatment of severe pneumonia caused by Chlamydia psittaci complicated with acute respiratory distress syndrome during the COVID-19 pandemic

Introduction

Chlamydia psittaci infection in humans is a rare cause that mainly present as community-acquired pneumonia. Severe Chlamydia psittaci pneumonia can lead to acute respiratory distress syndrome (ARDS), septic shock, or multiple organ dysfunction with a mortality rate of 15%-20% before accurate diagnosis and targeted treatment. Metagenomic next-generation sequencing (mNGS) has an advantage in achieving early diagnosis. In the study, omadacycline implementation was described to provide a better understanding of effectiveness in severe psittacosis pneumonia with ARDS.

Methods

Sixteen patients with severe psittacosis pneumonia with ARDS were selected between September 2021 and October 2022. They were diagnosed using mNGS and treated with omadacycline. Retrospective analysis of clinical manifestations, laboratory data, disease progression, diagnostic tool, treatment, and prognosis was summarized.

Results

Common symptoms included fever, dyspnea, and cough. All patients developed ARDS, accompanied by septic shock (43.7%) and pulmonary embolism (43.7%). Laboratory data showed normal leucocytes, increased creatine kinase isoenzyme, and decreased albumin with liver dysfunction in most patients. All patients had increased neutrophils, C-reactive protein, procalcitonin, and D-dimer with decreased lymphocytes. Airspace consolidation, ground glass opacity, and pleural effusion were found on chest CT. mNGS results were obtained in 24-48 h to identify the diagnosis of Chlamydia psittacosis. All patients received mechanical ventilation with omadacycline treatment. Fourteen patients experienced complete recovery, while the other two patients died from multidrug-resistant bacterial infection and renal failure.

Conclusion

mNGS has a significant value in the diagnosis of Chlamydia psittaci infection. Timely treatment of omadacycline can improve prognosis and provide a promising new option for the treatment of severe Chlamydia psittaci pneumonia with ARDS.

Postmortem diagnosis of gestational psittacosis: A case report

Background

Gestational psittacosis is one of the causes of unanticipated maternal death but has been difficult to diagnose early in clinical practice.

Case Presentation

A 28-year-old woman who was 7 months pregnant experienced flu-like symptoms, which deteriorated. She was brought to our hospital in shock, and the fetus was nonviable. The patient was diagnosed with pneumonia and septic shock and administered meropenem. Despite aggressive resuscitation, she died 7 h after symptom onset. After obtaining consent from the patient's family, the autopsy was done to identify the cause of death. Microscopically, there was intervillous neutrophil accumulation in the placenta. Genetic analysis detected the Chlamydia psittaci gene in several organs, including placenta.

Conclusion

Gestational psittacosis should be considered for a pregnant woman with flu-like symptoms. Moreover, unanticipated death of a pregnant woman might warrant a detailed autopsy to reveal the cause of death.

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 Pneumonia-Induced Pulmonary Thrombosis: A Case Report

Chlamydia psittaci pneumonia frequently leads to various extrapulmonary complications; however, reports of C. psittaci-pneumonia complicated by pulmonary thrombosis are uncommon. We report a case of severe C. psittaci pneumonia in a patient with a history of poultry contact and clinical manifestations including hyperpyrexia, dyspnea, and respiratory failure, which necessitated tracheal intubation for assisted ventilation. C. psittaci in bronchoalveolar lavage fluid was detected with metagenomic next-generation sequencing. Following targeted antibiotic therapy, the fever subsided, although dyspnea persisted without significant improvement, and chest pain developed. Compared to previous measurements, the D-dimer level increased, and CT pulmonary angiography revealed thromboses in the pulmonary artery trunk and left pulmonary artery. The symptoms improved after anticoagulant treatment, and the patient was discharged subsequently. This study suggests that C. psittaci infection may be associated with the formation of pulmonary thrombosis. Additional clinical data are required to support this inference. Following targeted antibiotic therapy, if persistent dyspnea, chest pain, and increased D-dimer level are present, pulmonary thrombosis should be considered, and pulmonary artery angiography can confirm the diagnosis.

Clinical features of psittacosis in 46 Chinese patients

BACKGROUND

Psittacosis is a relatively uncommon cause of community-acquired pneumonia, often leading to diagnostic difficulty.

METHODS

A retrospective study was conducted on the clinical features of psittacosis patients in China. Forty-six cases of Chlamydophila psittaci infection with atypical pneumonia of varying severity in the last two years were described retrospectively.

RESULTS

Fever, relative bradycardia, and other systemic upsets were the main clinical presentation. The most common radiographic abnormality was segmental or lobar shadowing or consolidation. The total white cell counts were usually normal or slightly increased. The concentration of creatine kinase, C reactive protein, and lactic dehydrogenase increased, while albumin decreased remarkably. These cases exhibited good recovery after being treated with tetracycline or quinolone antibiotics.

CONCLUSION

These features may help differentiate psittacosis from other traditional bacterial pneumonia. However, they do not provide a definitive diagnosis. Psittacosis diagnosis must perform the whole-genome sequencing for Chlamydophila psittaci in respiratory, blood, or sputum specimens. Increased awareness of psittacosis can shorten diagnostic delays and improve patient outcomes.

Review of bioaerosols from different sources and their health impacts

The emission of bioaerosols in the ambient atmosphere from different sources is a cause of concern for human health and the environment. Bioaerosols are a combination of biotic matter like microbes and pollens. The present review emphasizes the understanding of various sources of bioaerosols (industries, municipal solid waste, and medical facilities), their components, and their impact on human health. The study of bioaerosols is of great importance as large numbers of people are estimated to be exposed on the global scale. Bioaerosols exposure in different work environments results in health issues such as infectious diseases, allergies, toxic effects, and respiratory problems. Hence, extensive research is urged to establish an effective assessment of bioaerosols exposure in the workplace, risks involved, distribution, and validation. The present review is intended to explore the relationship between bioaerosols exposure to the atmosphere and its impacts on human health. Some of the preliminary findings, based on our analysis of bioaerosols arising from municipal solid waste at a landfill site and a waste transfer station in Hyderabad, India, are also discussed herein.

Co-infection of Chlamydia psittaci and Tropheryma whipplei: A case report

BACKGROUND

The co-infection of Chlamydia psittaci (C. psittaci) and Tropheryma whipplei (T. whipplei) is unusual, and the detection of pathogenic microorganisms is particularly important for patients with severe diseases or poor experience in treatment. Early identification of pathogens can significantly improve the prognosis of the patients. Targeted next-generation sequencing (tNGS) is currently widely used in clinical practice for various infectious diseases, including respiratory infections, to achieve early, accurate, and rapid microbial diagnosis.

CASE SUMMARY

We report a case of a 40-year-old female patient with a history of contact with parrots who was diagnosed with C. psittaci and T. whipplei infection through bronchial lavage fluid targeted next generation sequencing. After moxifloxacin treatment, the patient's symptoms improved significantly, and the imaging changes were obviously resolved.

CONCLUSION

Coinfection with C. psittaci and T. whipplei is not common. In this case, timely and accurate identification of both pathogens was achieved using tNGS. Moreover, the efficacy of monotherapy with moxifloxacin was confirmed.

Acute abdominal pain as the first symptom of Chlamydia psittaci pneumonia complicated by acute pancreatitis: a case report

Background

Chlamydia psittaci infections primarily cause damage to the lungs but may also affect the cardiovascular system, gastrointestinal tract, liver, kidney, and brain, resulting in a variety of extrapulmonary complications. However, reports regarding C. psittaci infection-associated pancreatitis are rare. In this report, a patient with C. psittaci pneumonia complicated by acute pancreatitis is presented.

Case description

The patient presented with acute upper abdominal pain and developed severe pyrexia and dyspnoea one day later. A chest computed tomography image revealed patchy consolidation in the left lung. The disease progressed rapidly, and the patient exhibited liver and kidney damage and type 1 respiratory failure within a short period of time. Metagenomic next-generation sequencing of alveolar lavage fluid revealed the presence of C. psittaci. The patient was administered doxycycline and moxifloxacin, after which the patient's abdominal pain and lung infection significantly resolved.

Conclusion

This case report demonstrates that extrapulmonary C. psittaci infections due to secondary acute pancreatitis can manifest as abdominal pain, although the exact mechanisms of C. psittaci caused by acute pancreatitis remain unclear. Timely diagnoses and treatments of such infections are necessary to achieve favorable clinical outcomes.

Chlamydia psittaci seropositivity in workers exposed to birds and review of the literature: Evidence of circulation in Antioquia

Introduction

Psittacosis is a zoonotic disease caused by Chlamydia psittaci, a bacterium classified as an agent with bioterrorist potential. It has caused multiple outbreaks in exposed poultry workers around the world. Colombia has no epidemiological follow-up of the infection and a big knowledge gap.

Objectives

To determine the antibodies’ frequency against C. psittaci in workers with occupational exposure to birds and to review the literature on studies conducted in Colombia.

Materials and methods

We conducted a cross-sectional descriptive study with analytical intent on workers in contact with birds and reviewed the related literature in Colombia. IgM and IgG serum antibodies against C. psittaci were detected by microimmunofluorescence. The sociodemographic and exposure characteristics were expressed as frequencies and summary measures. Associated factors were explored by bivariate and multivariate analysis. The scientific and gray literature review was done with a structured search.

Results

We analyzed 54 workers in contact with birds. Antibody prevalence was 31.5%. Slaughtering and evisceration by non-veterinarians was a risk factor for antibody presence. There are only four previous studies on C. psittaci in Colombia.

Conclusions

Here, we present the first evidence of C. psittaci circulation among workers exposed to birds in Antioquia and the second report in the country. These findings contribute to the “One Health” public health strategy.

Clinical analysis of severe Chlamydia psittaci pneumonia: Case series study

The clinical characteristics and diagnosis of ten cases with severe Chlamydia psittaci pneumonia were analyzed. Ten patients had high fever, cough, or diarrhea, and all had a history of contact with birds or poultry. The white blood cell count of the patients was normal or slightly increased. The percentage of neutrophils (N%) and C reactive protein of the patients were significantly increased. Chest computer tomography showed patchy consolidation of both lungs, with one-sided lung lobes prominent, and bronchial inflation signs. All the patients were admitted to the intensive care unit due to respiratory failure. Nine patients needed ventilator-assisted ventilation therapy, and one patient needed high-flow oxygen therapy. All patients had sepsis, and five patients developed septic shock. The patients were diagnosed with severe C. psittaci pneumonia by clinical manifestations and contact history. After timely adjustment of tetracycline-based treatment, eight patients recovered and were discharged, and two patients died of septic shock and respiratory failure. Patients with poultry contact should be cautious toward C. psittaci pneumonia. A better method for the detection of C. psittaci is metagenomic next-generation sequencing. Its examination can shorten the diagnosis time. In a later stage, large-sample research is needed to guide clinical diagnosis and treatment.

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.

Psittacosis: An Underappreciated and Often Undiagnosed Disease

The bacterial agent Chlamydia psittaci, and the resulting disease of psittacosis, is a little-known and underappreciated infectious disease by healthcare practitioners and in public health in general. C. psittaci infections can cause significant psittacosis outbreaks, with person-to-person transmission documented in the last decade. In this publication, we review the pathogen and its disease, as well as examine the potential for genetic manipulation in this organism to create a more deadly pathogen. Recent disease surveys indicate that currently, the highest incidences of human disease exist in Australia, Germany and the UK. We recommend the universal public health reporting of C. psittaci and psittacosis disease and increasing the promotion of public health awareness.

Epidemiological and clinical characteristics of psittacosis among cases with complicated or atypical pulmonary infection using metagenomic next-generation sequencing: a multi-center observational study in China

BACKGROUND

Chlamydia psittaci (C. psittaci) causes parrot fever in humans. Development of metagenomic next-generation sequencing (mNGS) enables the identification of C. psittaci.

METHODS

This study aimed to determine the epidemiological and clinical characteristics of parrot fever cases in China. A multi-center observational study was conducted in 44 tertiary and secondary hospitals across 14 provinces and municipalities between April 2019 and October 2021.

RESULTS

A total of 4545 patients with complicated or atypical pulmonary infection were included in the study, among which the prevalence of C. psittaci was determined to be 2.1% using mNGS. The prevalence of C. psittaci was further determined across demographic groups and types of specimens. It was significantly higher in patients with senior age (2.6% in those > 50 years), winter-spring (3.6%; particularly in December, January, and February), and southwestern (3.4%) and central and southern China (2.7%) (each P < 0.001). Moreover, the prevalence was the highest in bronchoalveolar lavage fluid (BALF) (2.9%), compared with sputum (1.1%) and peripheral blood specimens (0.9%). Additionally, co-infection of principal microorganisms was compared. Certain microorganisms were more likely to co-infect in parrot fever cases, such as Candida albicans in BALF (26.7%) and peripheral blood (6.3%), compared with non-parrot fever cases (19.7% and 1.3%); however, they did not significantly differ (each P > 0.05).

CONCLUSION

Parrot fever remains low in patients with complicated or atypical pulmonary infection. It is likely to occur in winter-spring and southwestern region in China. BALF may be the optimal specimen in the application of mNGS. Co-infection of multiple microorganisms should be further considered.

Validation of JRS atypical pneumonia score in patients with community-acquired Chlamydia psittaci pneumonia

INTRODUCTION

The Japanese Respiratory Society (JRS) atypical pneumonia score is a useful tool for the rapid presumptive diagnosis of atypical pneumonia. We investigated the clinical features of community-acquired pneumonia (CAP) due to Chlamydia psittaci and validated the JRS atypical pneumonia score in patients with C. psittaci CAP.

METHODS

This study was conducted at 30 institutions and assessed a total of 72 sporadic cases with C. psittaci CAP, 412 cases with Mycoplasma pneumoniae CAP, and 576 cases with Streptococcus pneumoniae CAP.

RESULTS

Sixty-two of 72 patients with C. psittaci CAP had a history of avian exposure. Among the six parameters of the JRS score, matching rates of four parameters were significantly lower in the C. psittaci CAP than the M. pneumoniae CAP in the following parameters: age <60 years, no or minor comorbid illness, stubborn or paroxysmal cough, and absence of chest adventitious sounds. The sensitivity of the diagnosis of atypical pneumonia in patients with C. psittaci CAP was significantly lower than the M. pneumoniae CAP (65.3% and 87.4%, p < 0.0001). When the diagnostic sensitivity was analyzed for different ages, the diagnostic sensitivities for the C. psittaci CAP were 90.5% for non-elderly patients and 30.0% for elderly patients.

CONCLUSIONS

The JRS atypical pneumonia score is a useful tool for distinguishing between C. psittaci CAP and bacterial CAP in patients aged <60 years, but not in patients aged ≥60 years. A history of avian exposure in middle-aged patients with normal white blood cell count may be suggestive of C. psittaci pneumonia.