Underdiagnosis of Chlamydia trachomatis and Chlamydia psittaci revealed by introduction of respiratory multiplex PCR assay with Chlamydiaceae family primers

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.

Atypical Pathogens in Adult Community-Acquired Pneumonia and Implications for Empiric Antibiotic Treatment: A Narrative Review

Atypical pathogens are intracellular bacteria causing community-acquired pneumonia (CAP) in a significant minority of patients. Legionella spp., Chlamydia pneumoniae and psittaci, Mycoplasma pneumoniae, and Coxiella burnetii are commonly included in this category. M. pneumoniae is present in 5-8% of CAP, being the second most frequent pathogen after Streptococcus pneumoniae. Legionella pneumophila is found in 3-5% of inpatients. Chlamydia spp. and Coxiella burnetii are present in less than 1% of patients. Legionella longbeachae is relatively frequent in New Zealand and Australia and might also be present in other parts of the world. Uncertainty remains on the prevalence of atypical pathogens, due to limitations in diagnostic means and methodological issues in epidemiological studies. Despite differences between CAP caused by typical and atypical pathogens, the clinical presentation alone does not allow accurate discrimination. Hence, antibiotics active against atypical pathogens (macrolides, tetracyclines and fluoroquinolones) should be included in the empiric antibiotic treatment of all patients with severe CAP. For patients with milder disease, evidence is lacking and recommendations differ between guidelines. Use of clinical prediction rules to identify patients most likely to be infected with atypical pathogens, and strategies of narrowing the antibiotic spectrum according to initial microbiologic investigations, should be the focus of future investigations.

Diagnosis of severe Chlamydia psittaci pneumonia by metagenomic next-generation sequencing: 2 case reports

Psittacosis is a infectious disease caused by Chlamydia psittaci (C. psittaci), which presents as pneumonia in humans. The diagnosis of psittacosis is challenging, however, Metagenomic next-generation sequencing (MNGS) is very efficient. Herein we documented the clinical characteristics of two patients with severe C. psittaci pneumonia who were admitted to the Intensive Care Unit. C. psittaci nucleic acid sequences were detected by MNGS of bronchoalveolar lavage fluid from both patients. Doxycycline was administered and the treatment was effective. Implementation of MNGS is helpful for the early identification of pathogens, shortening the diagnosis and treatment time, and improving the prognosis of patients.

Extracorporeal Membrane Oxygenation in Severe Acute Respiratory Distress Syndrome Caused by Chlamydia psittaci: A Case Report and Review of the Literature

Background: Infection of Chlamydia psittaci (C. psittaci) could lead to serious clinical manifestations in humans, including severe pneumonia with rapid progression, adult respiratory distress syndrome (ARDS), sepsis, multiple organ dysfunction syndromes (MODS), and probably death. Implementation of extracorporeal membrane oxygenation (ECMO) in the patient with severe ARDS gives a promising new method for recovery.

Case Presentation: We report our successful use of venovenous (VV) ECMO in a 48-year-old man who manifested with severe respiratory distress syndrome, acute kidney injury, and septic shock caused by a diagnosis of pneumonia. After the combination of therapy including anti-infection, mechanical ventilation, and continuous renal replacement therapy (CRRT), acute inflammatory syndrome developed. However, his respiratory status rapidly deteriorated. Then, venoarterial (VA)-ECMO support was placed on the patient as suddenly slowing of the heart rate. Harlequin (North-South) syndrome occurred after ECMO initiation. A series of the process could not relieve hypoxia in the upper body. At last, transition to VV-ECMO improved hypoxia. The duration of VV-ECMO was 7 days and the mechanical ventilation was weaned on the next day. On the day of ECMO weaning, nanopore targeted sequencing (NTS) of bronchoalveolar lavage fluid (BALF) reported the presence of C. psittaci. After 19 days of critical systemic rehabilitation and combination therapy, the patient fully recovered from C. psittaci.

Conclusion: This is the first reported case of the patient receiving ECMO for C. psittaci pneumonia. ECMO puts the lungs on temporary rest, promotes the recovery of pulmonary function, and also wins time for finding the pathogens, which is crucial in the treatment of rare pathogens.

Clinical metagenomic sequencing for rapid diagnosis of pneumonia and meningitis caused by Chlamydia psittaci

BACKGROUND

Chlamydia psittaci (C. psittaci) is a gram-negative intracellular parasitic pathogenic bacterium that can infect avian and mammalian hosts, including humans. The detection of C. psittaci infections typically relies on traditional antigen-based immunoassays or serological testing that often lack sensitivity and/or specificity. Metagenomic next generation sequencing (mNGS) is an emerging tool for diagnosis.

AIM

To demonstrate that mNGS represents a valuable tool for rapid, sensitive, and accurate pathogen detection including C. psittaci infections.

METHODS

Four cases of psittacosis pneumonia and one case of pediatric psittacosis meningitis were diagnosed between December 2019 and May 2020 using mNGS at Changzhou Second People’s Hospital affiliated to Nanjing Medical University. Patients’ clinical characteristics, manifestations, and treatment histories were retrospectively evaluated.

RESULTS

All five patients had a history of exposure to wild (psittacine or other birds) or domesticated birds (chickens). All patients had a high fever (> 39℃) and three of them (60%) experienced organ insufficiency during the disease. The laboratory data showed normal to slightly increased leucocyte and neutrophil counts, and elevated procalcitonin levels in all five cases, and very high C-reactive protein levels in psittacosis pneumonia patients. mNGS identified a potential pathogen, C. psittaci, in patients’ bronchoalveolar lavage fluid or cerebrospinal fluid. Computed tomography revealed lung air-space consolidation, pleural thickening, and effusion fluid buildup in psittacosis pneumonia cases, and an arachnoid cyst in the right temporal lobe of the pediatric psittacosis meningitis patient. All patients experienced complete recovery following the administration of targeted anti-chlamydia therapy.

CONCLUSION

This study not only demonstrated that mNGS represents a valuable tool for rapid, sensitive, and accurate pathogen detection, but also raised public health concerns over C. psittaci infections.

Undiagnosed Cases of Human Pneumonia Following Exposure to Chlamydia psittaci from an Infected Rosella Parrot

This report describes two cases of occupational exposure to Chlamydia psittaci following dissection of an infected Rosella (Platycercus elegans). The C. psittaci infections (with one of them resulting in diagnosed pneumonia and hospitalisation) were undiagnosed during routine medical investigations but later established due to epidemiological and clinical evidence, and molecular testing of the archived Rosella’ specimens. This case report stresses the importance of correct application and interpretation of diagnostic tests and the need to raise awareness about this zoonotic pathogen among medical practitioners and people exposed to potential animal carriers. Our findings suggest other infected individuals might be misdiagnosed and that C. psittaci (psittacosis) is likely to be underreported in Australia. This case highlights the need to operationalise the One Health concept. We call for improved communication between human and animal health service providers to allow accurate and rapid diagnosis of this zoonotic disease and raised awareness among medical practitioners. Further targeted surveys of wild birds (and other animals) should be conducted to improve assessment of risks to the general population and people working with or exposed to wild birds.

Recent history of psittacosis in Australia: expanding our understanding of the epidemiology of this important globally distributed zoonotic disease

Psittacosis is a human systemic disease caused by infection with Chlamydia psittaci. Shortly after reports emerged of a global pandemic associated with contact with imported parrots, Australian researchers including Macfarlane Burnet and others demonstrated that C. psittaci was widespread in Australian parrots. Australian cases over the last two decades have revealed that environmental exposure and contact with infected horses are also risk factors in an increasingly complicated epidemiological picture for this zoonotic disease.

Next-generation sequencing diagnosis of severe pneumonia from fulminant psittacosis with multiple organ failure: a case report and literature review

This study includes a retrospective analysis of the diagnosis and treatment of a case of severe pneumonia from fulminant psittacosis with multiple organ failure. Next-generation sequencing (NGS) of the pathogen was conducted. The purpose of this study was to summarize the clinical, laboratory, and imaging characteristics of the case and to improve understanding of the value of NGS in the diagnosis of severe community-acquired pneumonia (CAP). Fulminant psittacosis can be manifested as severe pneumonia with rapid progression, acute respiratory distress syndrome, sepsis, and multiple organ failure. Imaging shows unilateral lung consolidation, which is difficult to differentiate from CAP caused by common pathogens. The NGS technology can early detect rare pathogens, thus reducing unnecessary use of antibiotics and shortening the course of the disease.

Establishment of a Multiplex Real-Time TaqMan-MGB Polymerase Chain Reaction (PCR) Method for the Simultaneous Detection of Three Animal Chlamydia Species

BACKGROUND Chlamydiae are spread globally and cause infectious diseases in both humans and animals. The existing detection methods for this disease have numerous shortcomings, including low sensitivity, time consuming procedures, and high contamination vulnerability. MATERIAL AND METHODS To overcome shortcomings for detecting animal chlamydiosis, a multiplex quantitative polymerase chain reaction (PCR) assay was established for simultaneously detecting and differentiating 3 Chlamydia species (C. pecorum, C. abortus, and C. psittaci) by real time PCR based on TaqMan-MGB technology. RESULTS The limit of detection was 20.2 copies/µL for Chlamydophila (Cp.) abortus, 30.8 copies/µL for Cp. pecorum, and 16 copies/µL for Cp. psittaci. This method has good repeatability and stability as coefficients of variation range from 0.04% to 1.38%. Furthermore, compared with OIE (World Organization for Animal Health) recommended PCR assay and previously reported animal chlamydia shell PCR, this multiplex PCR assay demonstrated 99% concordance in detecting clinical samples of porcine nasal swabs and vaginal swabs. CONCLUSIONS The novel established method in this study was able to detect 3 types of Chlamydia species simultaneously, and had high sensitivity, strong specificity, and good stability. It provided a rapid, reliable, and convenient method for epidemiological and clinical diagnosis of chlamydiosis in animals.

Chlamydiae from Down Under: The Curious Cases of Chlamydial Infections in Australia

In Australia, the most researched and perhaps the most successful chlamydial species are the human pathogen Chlamydia trachomatis, animal pathogens Chlamydia pecorum and Chlamydia psittaci. C. trachomatis remains the leading cause of sexually transmitted infections in Australians and trachoma in Australian Indigenous populations. C. pecorum is globally recognised as the infamous koala and widespread livestock pathogen, whilst the avian C. psittaci is emerging as a horse pathogen posing zoonotic risks to humans. Certainly not innocuous, the human infections with Chlamydia pneumoniae seem to be less prevalent that other human chlamydial pathogens (namely C. trachomatis). Interestingly, the complete host range for C. pecorum and C. psittaci remains unknown, and infections by other chlamydial organisms in Australian domesticated and wildlife animals are understudied. Considering that chlamydial organisms can be encountered by either host at the human/animal interface, I review the most recent findings of chlamydial organisms infecting Australians, domesticated animals and native wildlife. Furthermore, I also provide commentary from leading Australian Chlamydia experts on challenges and future directions in the Chlamydia research field.

Gestational Psittacosis Resulting in Neonatal Death Identified by Next-Generation RNA Sequencing of Postmortem, Formalin-Fixed Lung Tissue

Psittacosis is a rare zoonosis that can cause severe disease and adverse outcomes during pregnancy. We identified a previously elusive case of psittacosis causing premature delivery and infant death by next-generation RNA sequencing of postmortem tissues. Hypothesis-free pathogen detection in postmortem specimens can increase the yield of epidemiologic and cause-of-death studies.