Zoonotic Chlamydiae as rare causes of severe pneumonia.

Zoonotic species of the Chlamydiaceae family should be considered as rare pathogenic agents of severe atypical pneumonia. A fatal case of a severe pneumonia due to Chlamydia psittaci was traced back to pet birds, and pneumonia in a pregnant woman was attributed to abortions in a sheep and goat flock, being the source of Chlamydia abortus. The two SARS­CoV­2-negative pneumonia cases presented here were investigated in an inter-disciplinary approach involving physicians and veterinarians. State-of-art molecular methods allowed the identification and genotyping of zoonotic Chlamydiae.

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

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

Human-to-human transmission of Chlamydia psittaci in China, 2020: an epidemiological and aetiological investigation.

BACKGROUND: Chlamydia psittaci can infect a wide range of avian species, occasionally causing psittacosis (also known as parrot fever) in humans. Most human psittacosis cases are associated with close contact with pet birds or poultry. In December, 2020, an outbreak of severe community-acquired pneumonia of unknown aetiology was reported in a hospital in Shandong province, China, and some of the patients' close contacts had respiratory symptoms. Our aims were to determine the causative agent of this epidemic and whether there had been human-to-human transmission. METHODS: For this epidemiological and aetiological investigation study, we enrolled patients who had community-acquired pneumonia confirmed by chest CT at two local hospitals in Shandong Province in China. We collected sputum, bronchoalveolar lavage fluid, and nasopharyngeal swab samples from participants and detected pathogens by surveying for 22 target respiratory microbes using a commercial assay, followed by metagenomic next-generation sequencing, specific nested PCR, and qPCR tests. We excluded individuals who were C psittaci-negative on both tests. We recruited close contacts of the C psittaci-positive patients, and tested nasopharyngeal swabs from the close contacts and samples from ducks from the processing plant where these patients worked. We then integrated the epidemiological, clinical, and laboratory data to reveal the potential chain of transmission of C psittaci that characterised this outbreak. FINDINGS: Between Dec 4 and 29, 2020, we used metagenomic next-generation sequencing and different PCR-based approaches to test 12 inpatients with community-acquired pneumonia, of whom six (50%) were workers at a duck-meat processing plant and two (17%) were unemployed people, who were positive for C psittaci and enrolled in this study. We contacted 61 close contacts of the six patients who worked at the duck-meat processing plant, of whom 61 (100%) were enrolled and tested, and we determined that the community-acquired pneumonia outbreak was caused by C psittaci. Within the outbreak cluster, 17 (77%) of 22 participants had confirmed C psittaci infections and five (23%) of 22 participants were asymptomatic C psittaci carriers. The outbreak had begun with avian-to-human transmission, and was followed by secondary and tertiary human-to-human transmission, which included transmission by several asymptomatic carriers and by health-care workers. In addition, some of the participants with confirmed C psittaci infection had no identified source of infection, which suggested cryptic bacterial transmission. INTERPRETATION: Our study data might represent the first documented report of human-to-human transmission of C psittaci in China. Therefore, C psittaci has the potential to evolve human-to-human transmission via various routes, should be considered an elevated biosecurity and emergent risk, and be included as part of the routine diagnosis globally, especially for high-risk populations. FUNDING: Academic Promotion Programme of Shandong First Medical University, National Science and Technology Major Project, ARC Australian Laureate Fellowship.

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

OBJECTIVES: Here, we retrospectively described the diagnosis and treatment of 32 cases diagnosed with Chlamydia psittaci pneumonia during the COVID-19 pandemic. METHODS: Clinical information was collected from all the patients. Reverse transcription-PCR and ELISAs were conducted for the detection of COVID-19 using nasal swabs and bronchoalveolar lavage fluid (BALF) samples. Metagenomic next-generation sequencing (mNGS) was performed for the identification of causative pathogens using BALF, peripheral blood and sputum samples. End-point PCR was performed to confirm the mNGS results. RESULTS: All 32 patients showed atypical pneumonia and had infection-like symptoms that were similar to COVID-19. Results of reverse transcription-PCR and ELISAs ruled out COVID-19 infection. mNGS identified C. psittaci as the suspected pathogen in these patients within 48 hours, which was validated by PCR, except for three blood samples. The sequence reads that covered fragments of C. psittaci genome were detected more often in BALF than in sputum or blood samples. All patients received doxycycline-based treatment regimens and showed favorable outcomes. CONCLUSION: This retrospective study, with the highest number of C. psittaci pneumonia enrolled cases in China so far, suggests that human psittacosis may be underdiagnosed and misdiagnosed clinically, especially in the midst of the COVID-19 pandemic.

Clustering Cases of Chlamydia psittaci Pneumonia in Coronavirus Disease 2019 Screening Ward Staff.

We describe 4 cases of Chlamydia psittaci pneumonia among medical staff in a coronavirus disease 2019 (COVID-19) screening ward, as well as the experience of dealing with this nosocomial infection event. Atypical pneumonia, in addition to COVID-19, should be considered when clustering cases occur, even during a COVID-19 pneumonia pandemic.

Metagenomic next-generation sequencing in the family outbreak of psittacosis: the first reported family outbreak of psittacosis in China under COVID-19.

Chlamydia psittaci infection in humans, also known as psittacosis, is usually believed to be an uncommon disease which mainly presents as community-acquired pneumonia (CAP). It is usually sporadic, but outbreaks of infection may occasionally occur. In outbreaks, diagnosis and investigations were usually hampered by the non-specificity of laboratory testing methods to identify C. psittaci. In this study, we use metagenomic next-generation sequencing (mNGS) in the diagnosis of a family outbreak of psittacosis under COVID-19. Three members of an extended family of 6 persons developed psittacosis with pneumonia and hepatic involvement with common symptoms of fever and weakness. Two newly purchased pet parrots, which had died successively, were probably the primary source of infection. Imagings show lung consolidations and infiltrates, which are difficult to be differentiated from CAP caused by other common pathogens. mNGS rapidly identified the infecting agent as C. psittaci within 48 h. The results of this work suggest that there are not characteristic clinical manifestations and imagings of psittacosis pneumonia which can differentiate from CAP caused by other pathogens. The use of mNGS can improve accuracy and reduce the delay in the diagnosis of psittacosis especially during the outbreak, which can shorten the course of the disease control. Family outbreak under COVID-19 may be related to the familial aggregation due to the epidemic. To our knowledge, this is the first reported family outbreak of psittacosis in China, and the first reported psittacosis outbreak identified by the method of mNGS in the world.